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Page 1: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 138

Osswald Menges

Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 238

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 338

Material Science

of Polymersfor Engineers

Tim A Osswald

Georg Menges

Hanser Publishers Munich Hanser Publications Cincinnati

3rd Edition

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 438

Te Author

Pro Dr im A OsswaldUniversity o Wisconsin-Madison Polymer Processing Research GroupDepartment o Mechanical Engineering 1513 University Avenue Madison USA

Pro Dr-Ing Georg MengesAm Beulardstein 19 Aachen Germany

Distributed in North and South America byHanser Publications6915 Valley Avenue Cincinnati Ohio 45244-3029 USAFax (513) 527-8801Phone (513) 527-8977wwwhanserpublicationscom

Distributed in all other countries byCarl Hanser VerlagPostach 86 04 20 81631 Muumlnchen GermanyFax +49 (89) 98 48 09wwwhanserde

Te use o general descriptive names trademarks etc in this publication even i the ormer are not especiallyidentified is not to be taken as a sign that such names as understood by the rade Marks and Merchandise MarksAct may accordingly be used reely by anyoneWhile the advice and inormation in this book are believed to be true and accurate at the date o going to pressneither the authors nor the editors nor the publisher can accept any legal responsibility or any errors or omissionsthat may be made Te publisher makes no warranty express or implied with respect to the material containedherein

Library o Congress Cataloging-in-Publication Data

Osswald im A Material science o polymers or engineers im A Osswald Georg Menges -- 3rd edition pages cm Includes bibliographical reerences and indexes ISBN 978-1-56990-514-2 (hardcover) -- ISBN (invalid) 978-1-56990-524-1 (e-book) 1 Polymers 2 Plastics--Molding I Menges Georg 1923- II itle

P1120O848 2012 6689--dc23

2012019893

Bibliografische Inormation Der Deutschen BibliothekDie Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografiedetaillierte bibliografische Daten sind im Internet uumlber lthttpdnbd-nbdegt abrufar

ISBN 978-1-56990-514-2E-Book-ISBN 9781569905241

All rights reserved No part o this book may be reproduced or transmitted in any orm or by any meanselectronic or mechanical including photocopying or by any inormation storage and retrieval systemwithout permission in writing rom the publisher

copy Carl Hanser Verlag Munich 2010Production Management Steffen Joumlrg

Coverconcept Marc Muumlller-Bremer wwwrebrandingde MuumlnchenCoverdesign Stephan Roumlnigk ypeset printed and bound by Koumlsel KrugzellPrinted in Germany

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 538

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 638

VI Preface to the First Edition

are grateul to Richard Theriault or prooreading the entire manuscript We also

thank the ollowing people who helped prooread or gave suggestions during the

preparation o the book Susanne Belovari Bruce A Davis Jeffrey Giacomin Paul J

Gramann Matthew Kaegebein Gwan-Wan Lai Maria del Pilar Noriega E Antoine C

Rios B Linards U Stradins and Ester M Sun Susanne Belovari and Andrea Jung-Mack are acknowledged or translating portions o Werkstoffkunde Kunststoffe rom

German to English We also thank Tara Ruggiero or preparing the camera-ready

manuscript Many o the figures were taken rom class notes o the mechanical engi-

neering senior elective course Engineering Design with Polymers Special thanks

are offered to Lynda Litzkow Philipp Ehrenstein and Bryan Hutchinson or the

superb job o drawing those figures Matthias Mahlke o Bayer AG in Leverkusen

Germany Laura Dietsche Joseph Dooley and Kevin Hughes o Dow Chemical in Mid-

land Michigan and Mauricio DeGrei and Juan Diego Sierra o the ICIPC in Medelliacuten

Colombia are acknowledged or some o the figures Thanks are due to Marcia

Sanders or copy editing the final manuscript We are grateul to Wolgang Glenz

Martha Kuumlrzl Ed Immergut and Carol Radtke o Hanser Publishers or their support

throughout the development o this book Above all the authors thank their wives

or their patience

Summer 1995

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

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The first edition o this book was adopted by several universities in North and

South America Europe and Asia as a textbook to introduce engineering students

to the materials science o polymers The book was also translated into Japanese in

1998 Korean in 1999 and Spanish in 2008 The proessors who taught with thefirst and second editions as well as their students liked the unified approach we

took The changes and additions that were introduced in this edition are based on

suggestions rom these proessors and their students as well as rom our own

experience using it as a class textbook

Afer two revisions and two decades o teaching it has become clear that sustaina-

bility and profits are important when dealing with polymeric materials Thereore

the 4Prsquos o the first edition have expanded to the 6Prsquos in the third edition polymer

processing product perormace post-consumer lie and profit In the last 18

years this book has become a reerence or many practicing engineers most o

whom were introduced to the book as students The first and second editions were

praised because o the vast number o graphs and data that can be used as reer-

ences We have urther strengthened this attribute by expanding a comprehensive

table in the appendix that contains material property graphs or several polymers

Furthermore in this edition we added color to the figures and graphs making the

book more appealing to the reader

With this edition we owe our gratitude to Dr Christine Strohm or editing the book

and catching those small typos and inconsistencies in the text and equations Wethank Dr Nadine Warkotsch and Steffen Joerg o Hanser Publishers or their coop-

eration during the production o this book We are grateul to Luz Mayed D

Nouguez and Tobias Mattner or the superb job drawing the figures and to Tobias

Mattner or his suggestions on how to make many o the figures more understand-

able A special thanks to Katerina Saacutenchez or the graphs related to recycling o

plastics in Chapter 1 and to Nora Catalina Restrepo or generating the polymer

statistic graphs in Chapter 2 My graduate students Roberto Monroy Luisa Loacutepez

Tom Mulholland Jakob Onken Camilo Peacuterez Daniel Ramiacuterez Jochen Wellekoetter

and Yuxiao Zhang organized by William Aquite supplied extra problems and solu-

tions or the third edition thank you Special thanks to Diane or ndash as always ndash

serving as a sounding board and advisor during this project

Spring 2012

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

Preface to the

Third Edition

3

Z e i l e n

Uuml b e r s a t z

b i t t e

k uuml r z e n

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7252019 CH-1Material Science of Polymers for Engineers

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Contents

Preface to the First Edition V

Preface to the Third Edition VII

983089 Introduction 983091

983089983089 The 983094 Prsquos 983091

983089983090 General Information 983094

983089983091 Identification of Polymers 983089983091

983089983092 Sustainability ndash The 983094th P 983089983093

References 983090983088

983090 Historical Background 983090983089

983090983089 From Natural to Synthetic Rubber 983090983089

983090983090 Cellulose and the $983089983088983088983088983088 Idea 983090983095

983090983091 Galalith ndash The Milk Stone 983091983088

983090983092 Leo Baekeland and the Plastics Industry 983091983089

983090983093 Herman Mark and the American Polymer Education 983091983092

983090983094 Wallace Hume Carothers and Synthetic Polymers 983091983095

983090983095 Polyethylene ndash A Product of Brain and Brawn 983091983097

983090983096 The Super Fiber and the Woman Who Invented It 983092983090

983090983097 One Last Word ndash Plastics 983092983092

References 983092983095

983091 Structure of Polymers 983092983097

983091983089 Macromolecular Structure of Polymers 983092983097983091983090 Molecular Bonds and Inter-Molecular Attraction 983093983088

983091983091 Molecular Weight 983093983089

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X Contents

983091983092 Conformation and Configuration of Polymer Molecules 983093983094

983091983093 Arrangement of Polymer Molecules 983093983097

983091983093983089 Thermoplastic Polymers 983094983088

983091983093983090 Amorphous Thermoplastics 983094983088

983091983093983091 Semi-Crystalline Thermoplastics 983094983090

983091983093983092 Thermosets and Cross-Linked Elastomers 983095983090

983091983094 Copolymers and Polymer Blends 983095983091

983091983095 Polymer Additives 983095983093

983091983095983089 Flame Retardants 983095983093

983091983095983090 Stabilizers 983095983095

983091983095983091 Antistatic Agents 983095983096

983091983095983092 Fillers 983095983096

983091983095983093 Blowing Agents 983095983097

References 983096983090

983092 Thermal Properties of Polymers 983096983091

983092983089 Material Properties 983096983093

983092983089983089 Thermal Conductivity 983096983093

983092983089983090 Specific Heat 983097983089

983092983089983091 Density 983097983091

983092983089983092 Thermal Diffusivity 983097983094 983092983089983093 Linear Coefficient of Thermal Expansion 983097983095

983092983089983094 Thermal Penetration 983097983096

983092983089983095 Glass Transition Temperature 983097983097

983092983089983096 Melting Temperature 983097983097

983092983090 Measuring Thermal Data 983097983097

983092983090983089 Differential Thermal Analysis (DTA) 983089983088983088

983092983090983090 Differential Scanning Calorimeter (DSC) 983089983088983089

983092983090983091 Thermomechanical Analysis (TMA) 983089983088983091 983092983090983092 Thermogravimetry (TGA) 983089983088983092

983092983090983093 Density Measurements 983089983088983093

References 983089983088983097

983093 Rheology of Polymer Melts 983089983089983089

983093983089 Introduction 983089983089983089

983093983089983089 Continuum Mechanics 983089983089983089

983093983089983090 The Generalized Newtonian Fluid 983089983089983091983093983089983091 Normal Stresses in Shear Flow 983089983089983093

983093983089983092 Deborah Number 983089983089983094

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XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

7252019 CH-1Material Science of Polymers for Engineers

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 2: CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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Material Science

of Polymersfor Engineers

Tim A Osswald

Georg Menges

Hanser Publishers Munich Hanser Publications Cincinnati

3rd Edition

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 438

Te Author

Pro Dr im A OsswaldUniversity o Wisconsin-Madison Polymer Processing Research GroupDepartment o Mechanical Engineering 1513 University Avenue Madison USA

Pro Dr-Ing Georg MengesAm Beulardstein 19 Aachen Germany

Distributed in North and South America byHanser Publications6915 Valley Avenue Cincinnati Ohio 45244-3029 USAFax (513) 527-8801Phone (513) 527-8977wwwhanserpublicationscom

Distributed in all other countries byCarl Hanser VerlagPostach 86 04 20 81631 Muumlnchen GermanyFax +49 (89) 98 48 09wwwhanserde

Te use o general descriptive names trademarks etc in this publication even i the ormer are not especiallyidentified is not to be taken as a sign that such names as understood by the rade Marks and Merchandise MarksAct may accordingly be used reely by anyoneWhile the advice and inormation in this book are believed to be true and accurate at the date o going to pressneither the authors nor the editors nor the publisher can accept any legal responsibility or any errors or omissionsthat may be made Te publisher makes no warranty express or implied with respect to the material containedherein

Library o Congress Cataloging-in-Publication Data

Osswald im A Material science o polymers or engineers im A Osswald Georg Menges -- 3rd edition pages cm Includes bibliographical reerences and indexes ISBN 978-1-56990-514-2 (hardcover) -- ISBN (invalid) 978-1-56990-524-1 (e-book) 1 Polymers 2 Plastics--Molding I Menges Georg 1923- II itle

P1120O848 2012 6689--dc23

2012019893

Bibliografische Inormation Der Deutschen BibliothekDie Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografiedetaillierte bibliografische Daten sind im Internet uumlber lthttpdnbd-nbdegt abrufar

ISBN 978-1-56990-514-2E-Book-ISBN 9781569905241

All rights reserved No part o this book may be reproduced or transmitted in any orm or by any meanselectronic or mechanical including photocopying or by any inormation storage and retrieval systemwithout permission in writing rom the publisher

copy Carl Hanser Verlag Munich 2010Production Management Steffen Joumlrg

Coverconcept Marc Muumlller-Bremer wwwrebrandingde MuumlnchenCoverdesign Stephan Roumlnigk ypeset printed and bound by Koumlsel KrugzellPrinted in Germany

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 638

VI Preface to the First Edition

are grateul to Richard Theriault or prooreading the entire manuscript We also

thank the ollowing people who helped prooread or gave suggestions during the

preparation o the book Susanne Belovari Bruce A Davis Jeffrey Giacomin Paul J

Gramann Matthew Kaegebein Gwan-Wan Lai Maria del Pilar Noriega E Antoine C

Rios B Linards U Stradins and Ester M Sun Susanne Belovari and Andrea Jung-Mack are acknowledged or translating portions o Werkstoffkunde Kunststoffe rom

German to English We also thank Tara Ruggiero or preparing the camera-ready

manuscript Many o the figures were taken rom class notes o the mechanical engi-

neering senior elective course Engineering Design with Polymers Special thanks

are offered to Lynda Litzkow Philipp Ehrenstein and Bryan Hutchinson or the

superb job o drawing those figures Matthias Mahlke o Bayer AG in Leverkusen

Germany Laura Dietsche Joseph Dooley and Kevin Hughes o Dow Chemical in Mid-

land Michigan and Mauricio DeGrei and Juan Diego Sierra o the ICIPC in Medelliacuten

Colombia are acknowledged or some o the figures Thanks are due to Marcia

Sanders or copy editing the final manuscript We are grateul to Wolgang Glenz

Martha Kuumlrzl Ed Immergut and Carol Radtke o Hanser Publishers or their support

throughout the development o this book Above all the authors thank their wives

or their patience

Summer 1995

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

7252019 CH-1Material Science of Polymers for Engineers

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The first edition o this book was adopted by several universities in North and

South America Europe and Asia as a textbook to introduce engineering students

to the materials science o polymers The book was also translated into Japanese in

1998 Korean in 1999 and Spanish in 2008 The proessors who taught with thefirst and second editions as well as their students liked the unified approach we

took The changes and additions that were introduced in this edition are based on

suggestions rom these proessors and their students as well as rom our own

experience using it as a class textbook

Afer two revisions and two decades o teaching it has become clear that sustaina-

bility and profits are important when dealing with polymeric materials Thereore

the 4Prsquos o the first edition have expanded to the 6Prsquos in the third edition polymer

processing product perormace post-consumer lie and profit In the last 18

years this book has become a reerence or many practicing engineers most o

whom were introduced to the book as students The first and second editions were

praised because o the vast number o graphs and data that can be used as reer-

ences We have urther strengthened this attribute by expanding a comprehensive

table in the appendix that contains material property graphs or several polymers

Furthermore in this edition we added color to the figures and graphs making the

book more appealing to the reader

With this edition we owe our gratitude to Dr Christine Strohm or editing the book

and catching those small typos and inconsistencies in the text and equations Wethank Dr Nadine Warkotsch and Steffen Joerg o Hanser Publishers or their coop-

eration during the production o this book We are grateul to Luz Mayed D

Nouguez and Tobias Mattner or the superb job drawing the figures and to Tobias

Mattner or his suggestions on how to make many o the figures more understand-

able A special thanks to Katerina Saacutenchez or the graphs related to recycling o

plastics in Chapter 1 and to Nora Catalina Restrepo or generating the polymer

statistic graphs in Chapter 2 My graduate students Roberto Monroy Luisa Loacutepez

Tom Mulholland Jakob Onken Camilo Peacuterez Daniel Ramiacuterez Jochen Wellekoetter

and Yuxiao Zhang organized by William Aquite supplied extra problems and solu-

tions or the third edition thank you Special thanks to Diane or ndash as always ndash

serving as a sounding board and advisor during this project

Spring 2012

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

Preface to the

Third Edition

3

Z e i l e n

Uuml b e r s a t z

b i t t e

k uuml r z e n

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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Contents

Preface to the First Edition V

Preface to the Third Edition VII

983089 Introduction 983091

983089983089 The 983094 Prsquos 983091

983089983090 General Information 983094

983089983091 Identification of Polymers 983089983091

983089983092 Sustainability ndash The 983094th P 983089983093

References 983090983088

983090 Historical Background 983090983089

983090983089 From Natural to Synthetic Rubber 983090983089

983090983090 Cellulose and the $983089983088983088983088983088 Idea 983090983095

983090983091 Galalith ndash The Milk Stone 983091983088

983090983092 Leo Baekeland and the Plastics Industry 983091983089

983090983093 Herman Mark and the American Polymer Education 983091983092

983090983094 Wallace Hume Carothers and Synthetic Polymers 983091983095

983090983095 Polyethylene ndash A Product of Brain and Brawn 983091983097

983090983096 The Super Fiber and the Woman Who Invented It 983092983090

983090983097 One Last Word ndash Plastics 983092983092

References 983092983095

983091 Structure of Polymers 983092983097

983091983089 Macromolecular Structure of Polymers 983092983097983091983090 Molecular Bonds and Inter-Molecular Attraction 983093983088

983091983091 Molecular Weight 983093983089

7252019 CH-1Material Science of Polymers for Engineers

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X Contents

983091983092 Conformation and Configuration of Polymer Molecules 983093983094

983091983093 Arrangement of Polymer Molecules 983093983097

983091983093983089 Thermoplastic Polymers 983094983088

983091983093983090 Amorphous Thermoplastics 983094983088

983091983093983091 Semi-Crystalline Thermoplastics 983094983090

983091983093983092 Thermosets and Cross-Linked Elastomers 983095983090

983091983094 Copolymers and Polymer Blends 983095983091

983091983095 Polymer Additives 983095983093

983091983095983089 Flame Retardants 983095983093

983091983095983090 Stabilizers 983095983095

983091983095983091 Antistatic Agents 983095983096

983091983095983092 Fillers 983095983096

983091983095983093 Blowing Agents 983095983097

References 983096983090

983092 Thermal Properties of Polymers 983096983091

983092983089 Material Properties 983096983093

983092983089983089 Thermal Conductivity 983096983093

983092983089983090 Specific Heat 983097983089

983092983089983091 Density 983097983091

983092983089983092 Thermal Diffusivity 983097983094 983092983089983093 Linear Coefficient of Thermal Expansion 983097983095

983092983089983094 Thermal Penetration 983097983096

983092983089983095 Glass Transition Temperature 983097983097

983092983089983096 Melting Temperature 983097983097

983092983090 Measuring Thermal Data 983097983097

983092983090983089 Differential Thermal Analysis (DTA) 983089983088983088

983092983090983090 Differential Scanning Calorimeter (DSC) 983089983088983089

983092983090983091 Thermomechanical Analysis (TMA) 983089983088983091 983092983090983092 Thermogravimetry (TGA) 983089983088983092

983092983090983093 Density Measurements 983089983088983093

References 983089983088983097

983093 Rheology of Polymer Melts 983089983089983089

983093983089 Introduction 983089983089983089

983093983089983089 Continuum Mechanics 983089983089983089

983093983089983090 The Generalized Newtonian Fluid 983089983089983091983093983089983091 Normal Stresses in Shear Flow 983089983089983093

983093983089983092 Deborah Number 983089983089983094

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7252019 CH-1Material Science of Polymers for Engineers

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XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

7252019 CH-1Material Science of Polymers for Engineers

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 1538

983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 3: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 338

Material Science

of Polymersfor Engineers

Tim A Osswald

Georg Menges

Hanser Publishers Munich Hanser Publications Cincinnati

3rd Edition

7252019 CH-1Material Science of Polymers for Engineers

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Te Author

Pro Dr im A OsswaldUniversity o Wisconsin-Madison Polymer Processing Research GroupDepartment o Mechanical Engineering 1513 University Avenue Madison USA

Pro Dr-Ing Georg MengesAm Beulardstein 19 Aachen Germany

Distributed in North and South America byHanser Publications6915 Valley Avenue Cincinnati Ohio 45244-3029 USAFax (513) 527-8801Phone (513) 527-8977wwwhanserpublicationscom

Distributed in all other countries byCarl Hanser VerlagPostach 86 04 20 81631 Muumlnchen GermanyFax +49 (89) 98 48 09wwwhanserde

Te use o general descriptive names trademarks etc in this publication even i the ormer are not especiallyidentified is not to be taken as a sign that such names as understood by the rade Marks and Merchandise MarksAct may accordingly be used reely by anyoneWhile the advice and inormation in this book are believed to be true and accurate at the date o going to pressneither the authors nor the editors nor the publisher can accept any legal responsibility or any errors or omissionsthat may be made Te publisher makes no warranty express or implied with respect to the material containedherein

Library o Congress Cataloging-in-Publication Data

Osswald im A Material science o polymers or engineers im A Osswald Georg Menges -- 3rd edition pages cm Includes bibliographical reerences and indexes ISBN 978-1-56990-514-2 (hardcover) -- ISBN (invalid) 978-1-56990-524-1 (e-book) 1 Polymers 2 Plastics--Molding I Menges Georg 1923- II itle

P1120O848 2012 6689--dc23

2012019893

Bibliografische Inormation Der Deutschen BibliothekDie Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografiedetaillierte bibliografische Daten sind im Internet uumlber lthttpdnbd-nbdegt abrufar

ISBN 978-1-56990-514-2E-Book-ISBN 9781569905241

All rights reserved No part o this book may be reproduced or transmitted in any orm or by any meanselectronic or mechanical including photocopying or by any inormation storage and retrieval systemwithout permission in writing rom the publisher

copy Carl Hanser Verlag Munich 2010Production Management Steffen Joumlrg

Coverconcept Marc Muumlller-Bremer wwwrebrandingde MuumlnchenCoverdesign Stephan Roumlnigk ypeset printed and bound by Koumlsel KrugzellPrinted in Germany

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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VI Preface to the First Edition

are grateul to Richard Theriault or prooreading the entire manuscript We also

thank the ollowing people who helped prooread or gave suggestions during the

preparation o the book Susanne Belovari Bruce A Davis Jeffrey Giacomin Paul J

Gramann Matthew Kaegebein Gwan-Wan Lai Maria del Pilar Noriega E Antoine C

Rios B Linards U Stradins and Ester M Sun Susanne Belovari and Andrea Jung-Mack are acknowledged or translating portions o Werkstoffkunde Kunststoffe rom

German to English We also thank Tara Ruggiero or preparing the camera-ready

manuscript Many o the figures were taken rom class notes o the mechanical engi-

neering senior elective course Engineering Design with Polymers Special thanks

are offered to Lynda Litzkow Philipp Ehrenstein and Bryan Hutchinson or the

superb job o drawing those figures Matthias Mahlke o Bayer AG in Leverkusen

Germany Laura Dietsche Joseph Dooley and Kevin Hughes o Dow Chemical in Mid-

land Michigan and Mauricio DeGrei and Juan Diego Sierra o the ICIPC in Medelliacuten

Colombia are acknowledged or some o the figures Thanks are due to Marcia

Sanders or copy editing the final manuscript We are grateul to Wolgang Glenz

Martha Kuumlrzl Ed Immergut and Carol Radtke o Hanser Publishers or their support

throughout the development o this book Above all the authors thank their wives

or their patience

Summer 1995

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

7252019 CH-1Material Science of Polymers for Engineers

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The first edition o this book was adopted by several universities in North and

South America Europe and Asia as a textbook to introduce engineering students

to the materials science o polymers The book was also translated into Japanese in

1998 Korean in 1999 and Spanish in 2008 The proessors who taught with thefirst and second editions as well as their students liked the unified approach we

took The changes and additions that were introduced in this edition are based on

suggestions rom these proessors and their students as well as rom our own

experience using it as a class textbook

Afer two revisions and two decades o teaching it has become clear that sustaina-

bility and profits are important when dealing with polymeric materials Thereore

the 4Prsquos o the first edition have expanded to the 6Prsquos in the third edition polymer

processing product perormace post-consumer lie and profit In the last 18

years this book has become a reerence or many practicing engineers most o

whom were introduced to the book as students The first and second editions were

praised because o the vast number o graphs and data that can be used as reer-

ences We have urther strengthened this attribute by expanding a comprehensive

table in the appendix that contains material property graphs or several polymers

Furthermore in this edition we added color to the figures and graphs making the

book more appealing to the reader

With this edition we owe our gratitude to Dr Christine Strohm or editing the book

and catching those small typos and inconsistencies in the text and equations Wethank Dr Nadine Warkotsch and Steffen Joerg o Hanser Publishers or their coop-

eration during the production o this book We are grateul to Luz Mayed D

Nouguez and Tobias Mattner or the superb job drawing the figures and to Tobias

Mattner or his suggestions on how to make many o the figures more understand-

able A special thanks to Katerina Saacutenchez or the graphs related to recycling o

plastics in Chapter 1 and to Nora Catalina Restrepo or generating the polymer

statistic graphs in Chapter 2 My graduate students Roberto Monroy Luisa Loacutepez

Tom Mulholland Jakob Onken Camilo Peacuterez Daniel Ramiacuterez Jochen Wellekoetter

and Yuxiao Zhang organized by William Aquite supplied extra problems and solu-

tions or the third edition thank you Special thanks to Diane or ndash as always ndash

serving as a sounding board and advisor during this project

Spring 2012

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

Preface to the

Third Edition

3

Z e i l e n

Uuml b e r s a t z

b i t t e

k uuml r z e n

7252019 CH-1Material Science of Polymers for Engineers

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Contents

Preface to the First Edition V

Preface to the Third Edition VII

983089 Introduction 983091

983089983089 The 983094 Prsquos 983091

983089983090 General Information 983094

983089983091 Identification of Polymers 983089983091

983089983092 Sustainability ndash The 983094th P 983089983093

References 983090983088

983090 Historical Background 983090983089

983090983089 From Natural to Synthetic Rubber 983090983089

983090983090 Cellulose and the $983089983088983088983088983088 Idea 983090983095

983090983091 Galalith ndash The Milk Stone 983091983088

983090983092 Leo Baekeland and the Plastics Industry 983091983089

983090983093 Herman Mark and the American Polymer Education 983091983092

983090983094 Wallace Hume Carothers and Synthetic Polymers 983091983095

983090983095 Polyethylene ndash A Product of Brain and Brawn 983091983097

983090983096 The Super Fiber and the Woman Who Invented It 983092983090

983090983097 One Last Word ndash Plastics 983092983092

References 983092983095

983091 Structure of Polymers 983092983097

983091983089 Macromolecular Structure of Polymers 983092983097983091983090 Molecular Bonds and Inter-Molecular Attraction 983093983088

983091983091 Molecular Weight 983093983089

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X Contents

983091983092 Conformation and Configuration of Polymer Molecules 983093983094

983091983093 Arrangement of Polymer Molecules 983093983097

983091983093983089 Thermoplastic Polymers 983094983088

983091983093983090 Amorphous Thermoplastics 983094983088

983091983093983091 Semi-Crystalline Thermoplastics 983094983090

983091983093983092 Thermosets and Cross-Linked Elastomers 983095983090

983091983094 Copolymers and Polymer Blends 983095983091

983091983095 Polymer Additives 983095983093

983091983095983089 Flame Retardants 983095983093

983091983095983090 Stabilizers 983095983095

983091983095983091 Antistatic Agents 983095983096

983091983095983092 Fillers 983095983096

983091983095983093 Blowing Agents 983095983097

References 983096983090

983092 Thermal Properties of Polymers 983096983091

983092983089 Material Properties 983096983093

983092983089983089 Thermal Conductivity 983096983093

983092983089983090 Specific Heat 983097983089

983092983089983091 Density 983097983091

983092983089983092 Thermal Diffusivity 983097983094 983092983089983093 Linear Coefficient of Thermal Expansion 983097983095

983092983089983094 Thermal Penetration 983097983096

983092983089983095 Glass Transition Temperature 983097983097

983092983089983096 Melting Temperature 983097983097

983092983090 Measuring Thermal Data 983097983097

983092983090983089 Differential Thermal Analysis (DTA) 983089983088983088

983092983090983090 Differential Scanning Calorimeter (DSC) 983089983088983089

983092983090983091 Thermomechanical Analysis (TMA) 983089983088983091 983092983090983092 Thermogravimetry (TGA) 983089983088983092

983092983090983093 Density Measurements 983089983088983093

References 983089983088983097

983093 Rheology of Polymer Melts 983089983089983089

983093983089 Introduction 983089983089983089

983093983089983089 Continuum Mechanics 983089983089983089

983093983089983090 The Generalized Newtonian Fluid 983089983089983091983093983089983091 Normal Stresses in Shear Flow 983089983089983093

983093983089983092 Deborah Number 983089983089983094

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XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

7252019 CH-1Material Science of Polymers for Engineers

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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7252019 CH-1Material Science of Polymers for Engineers

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 4: CH-1Material Science of Polymers for Engineers

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Te Author

Pro Dr im A OsswaldUniversity o Wisconsin-Madison Polymer Processing Research GroupDepartment o Mechanical Engineering 1513 University Avenue Madison USA

Pro Dr-Ing Georg MengesAm Beulardstein 19 Aachen Germany

Distributed in North and South America byHanser Publications6915 Valley Avenue Cincinnati Ohio 45244-3029 USAFax (513) 527-8801Phone (513) 527-8977wwwhanserpublicationscom

Distributed in all other countries byCarl Hanser VerlagPostach 86 04 20 81631 Muumlnchen GermanyFax +49 (89) 98 48 09wwwhanserde

Te use o general descriptive names trademarks etc in this publication even i the ormer are not especiallyidentified is not to be taken as a sign that such names as understood by the rade Marks and Merchandise MarksAct may accordingly be used reely by anyoneWhile the advice and inormation in this book are believed to be true and accurate at the date o going to pressneither the authors nor the editors nor the publisher can accept any legal responsibility or any errors or omissionsthat may be made Te publisher makes no warranty express or implied with respect to the material containedherein

Library o Congress Cataloging-in-Publication Data

Osswald im A Material science o polymers or engineers im A Osswald Georg Menges -- 3rd edition pages cm Includes bibliographical reerences and indexes ISBN 978-1-56990-514-2 (hardcover) -- ISBN (invalid) 978-1-56990-524-1 (e-book) 1 Polymers 2 Plastics--Molding I Menges Georg 1923- II itle

P1120O848 2012 6689--dc23

2012019893

Bibliografische Inormation Der Deutschen BibliothekDie Deutsche Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografiedetaillierte bibliografische Daten sind im Internet uumlber lthttpdnbd-nbdegt abrufar

ISBN 978-1-56990-514-2E-Book-ISBN 9781569905241

All rights reserved No part o this book may be reproduced or transmitted in any orm or by any meanselectronic or mechanical including photocopying or by any inormation storage and retrieval systemwithout permission in writing rom the publisher

copy Carl Hanser Verlag Munich 2010Production Management Steffen Joumlrg

Coverconcept Marc Muumlller-Bremer wwwrebrandingde MuumlnchenCoverdesign Stephan Roumlnigk ypeset printed and bound by Koumlsel KrugzellPrinted in Germany

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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VI Preface to the First Edition

are grateul to Richard Theriault or prooreading the entire manuscript We also

thank the ollowing people who helped prooread or gave suggestions during the

preparation o the book Susanne Belovari Bruce A Davis Jeffrey Giacomin Paul J

Gramann Matthew Kaegebein Gwan-Wan Lai Maria del Pilar Noriega E Antoine C

Rios B Linards U Stradins and Ester M Sun Susanne Belovari and Andrea Jung-Mack are acknowledged or translating portions o Werkstoffkunde Kunststoffe rom

German to English We also thank Tara Ruggiero or preparing the camera-ready

manuscript Many o the figures were taken rom class notes o the mechanical engi-

neering senior elective course Engineering Design with Polymers Special thanks

are offered to Lynda Litzkow Philipp Ehrenstein and Bryan Hutchinson or the

superb job o drawing those figures Matthias Mahlke o Bayer AG in Leverkusen

Germany Laura Dietsche Joseph Dooley and Kevin Hughes o Dow Chemical in Mid-

land Michigan and Mauricio DeGrei and Juan Diego Sierra o the ICIPC in Medelliacuten

Colombia are acknowledged or some o the figures Thanks are due to Marcia

Sanders or copy editing the final manuscript We are grateul to Wolgang Glenz

Martha Kuumlrzl Ed Immergut and Carol Radtke o Hanser Publishers or their support

throughout the development o this book Above all the authors thank their wives

or their patience

Summer 1995

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

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The first edition o this book was adopted by several universities in North and

South America Europe and Asia as a textbook to introduce engineering students

to the materials science o polymers The book was also translated into Japanese in

1998 Korean in 1999 and Spanish in 2008 The proessors who taught with thefirst and second editions as well as their students liked the unified approach we

took The changes and additions that were introduced in this edition are based on

suggestions rom these proessors and their students as well as rom our own

experience using it as a class textbook

Afer two revisions and two decades o teaching it has become clear that sustaina-

bility and profits are important when dealing with polymeric materials Thereore

the 4Prsquos o the first edition have expanded to the 6Prsquos in the third edition polymer

processing product perormace post-consumer lie and profit In the last 18

years this book has become a reerence or many practicing engineers most o

whom were introduced to the book as students The first and second editions were

praised because o the vast number o graphs and data that can be used as reer-

ences We have urther strengthened this attribute by expanding a comprehensive

table in the appendix that contains material property graphs or several polymers

Furthermore in this edition we added color to the figures and graphs making the

book more appealing to the reader

With this edition we owe our gratitude to Dr Christine Strohm or editing the book

and catching those small typos and inconsistencies in the text and equations Wethank Dr Nadine Warkotsch and Steffen Joerg o Hanser Publishers or their coop-

eration during the production o this book We are grateul to Luz Mayed D

Nouguez and Tobias Mattner or the superb job drawing the figures and to Tobias

Mattner or his suggestions on how to make many o the figures more understand-

able A special thanks to Katerina Saacutenchez or the graphs related to recycling o

plastics in Chapter 1 and to Nora Catalina Restrepo or generating the polymer

statistic graphs in Chapter 2 My graduate students Roberto Monroy Luisa Loacutepez

Tom Mulholland Jakob Onken Camilo Peacuterez Daniel Ramiacuterez Jochen Wellekoetter

and Yuxiao Zhang organized by William Aquite supplied extra problems and solu-

tions or the third edition thank you Special thanks to Diane or ndash as always ndash

serving as a sounding board and advisor during this project

Spring 2012

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

Preface to the

Third Edition

3

Z e i l e n

Uuml b e r s a t z

b i t t e

k uuml r z e n

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Contents

Preface to the First Edition V

Preface to the Third Edition VII

983089 Introduction 983091

983089983089 The 983094 Prsquos 983091

983089983090 General Information 983094

983089983091 Identification of Polymers 983089983091

983089983092 Sustainability ndash The 983094th P 983089983093

References 983090983088

983090 Historical Background 983090983089

983090983089 From Natural to Synthetic Rubber 983090983089

983090983090 Cellulose and the $983089983088983088983088983088 Idea 983090983095

983090983091 Galalith ndash The Milk Stone 983091983088

983090983092 Leo Baekeland and the Plastics Industry 983091983089

983090983093 Herman Mark and the American Polymer Education 983091983092

983090983094 Wallace Hume Carothers and Synthetic Polymers 983091983095

983090983095 Polyethylene ndash A Product of Brain and Brawn 983091983097

983090983096 The Super Fiber and the Woman Who Invented It 983092983090

983090983097 One Last Word ndash Plastics 983092983092

References 983092983095

983091 Structure of Polymers 983092983097

983091983089 Macromolecular Structure of Polymers 983092983097983091983090 Molecular Bonds and Inter-Molecular Attraction 983093983088

983091983091 Molecular Weight 983093983089

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X Contents

983091983092 Conformation and Configuration of Polymer Molecules 983093983094

983091983093 Arrangement of Polymer Molecules 983093983097

983091983093983089 Thermoplastic Polymers 983094983088

983091983093983090 Amorphous Thermoplastics 983094983088

983091983093983091 Semi-Crystalline Thermoplastics 983094983090

983091983093983092 Thermosets and Cross-Linked Elastomers 983095983090

983091983094 Copolymers and Polymer Blends 983095983091

983091983095 Polymer Additives 983095983093

983091983095983089 Flame Retardants 983095983093

983091983095983090 Stabilizers 983095983095

983091983095983091 Antistatic Agents 983095983096

983091983095983092 Fillers 983095983096

983091983095983093 Blowing Agents 983095983097

References 983096983090

983092 Thermal Properties of Polymers 983096983091

983092983089 Material Properties 983096983093

983092983089983089 Thermal Conductivity 983096983093

983092983089983090 Specific Heat 983097983089

983092983089983091 Density 983097983091

983092983089983092 Thermal Diffusivity 983097983094 983092983089983093 Linear Coefficient of Thermal Expansion 983097983095

983092983089983094 Thermal Penetration 983097983096

983092983089983095 Glass Transition Temperature 983097983097

983092983089983096 Melting Temperature 983097983097

983092983090 Measuring Thermal Data 983097983097

983092983090983089 Differential Thermal Analysis (DTA) 983089983088983088

983092983090983090 Differential Scanning Calorimeter (DSC) 983089983088983089

983092983090983091 Thermomechanical Analysis (TMA) 983089983088983091 983092983090983092 Thermogravimetry (TGA) 983089983088983092

983092983090983093 Density Measurements 983089983088983093

References 983089983088983097

983093 Rheology of Polymer Melts 983089983089983089

983093983089 Introduction 983089983089983089

983093983089983089 Continuum Mechanics 983089983089983089

983093983089983090 The Generalized Newtonian Fluid 983089983089983091983093983089983091 Normal Stresses in Shear Flow 983089983089983093

983093983089983092 Deborah Number 983089983089983094

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XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

7252019 CH-1Material Science of Polymers for Engineers

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

7252019 CH-1Material Science of Polymers for Engineers

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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7252019 CH-1Material Science of Polymers for Engineers

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 5: CH-1Material Science of Polymers for Engineers

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VI Preface to the First Edition

are grateul to Richard Theriault or prooreading the entire manuscript We also

thank the ollowing people who helped prooread or gave suggestions during the

preparation o the book Susanne Belovari Bruce A Davis Jeffrey Giacomin Paul J

Gramann Matthew Kaegebein Gwan-Wan Lai Maria del Pilar Noriega E Antoine C

Rios B Linards U Stradins and Ester M Sun Susanne Belovari and Andrea Jung-Mack are acknowledged or translating portions o Werkstoffkunde Kunststoffe rom

German to English We also thank Tara Ruggiero or preparing the camera-ready

manuscript Many o the figures were taken rom class notes o the mechanical engi-

neering senior elective course Engineering Design with Polymers Special thanks

are offered to Lynda Litzkow Philipp Ehrenstein and Bryan Hutchinson or the

superb job o drawing those figures Matthias Mahlke o Bayer AG in Leverkusen

Germany Laura Dietsche Joseph Dooley and Kevin Hughes o Dow Chemical in Mid-

land Michigan and Mauricio DeGrei and Juan Diego Sierra o the ICIPC in Medelliacuten

Colombia are acknowledged or some o the figures Thanks are due to Marcia

Sanders or copy editing the final manuscript We are grateul to Wolgang Glenz

Martha Kuumlrzl Ed Immergut and Carol Radtke o Hanser Publishers or their support

throughout the development o this book Above all the authors thank their wives

or their patience

Summer 1995

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

7252019 CH-1Material Science of Polymers for Engineers

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The first edition o this book was adopted by several universities in North and

South America Europe and Asia as a textbook to introduce engineering students

to the materials science o polymers The book was also translated into Japanese in

1998 Korean in 1999 and Spanish in 2008 The proessors who taught with thefirst and second editions as well as their students liked the unified approach we

took The changes and additions that were introduced in this edition are based on

suggestions rom these proessors and their students as well as rom our own

experience using it as a class textbook

Afer two revisions and two decades o teaching it has become clear that sustaina-

bility and profits are important when dealing with polymeric materials Thereore

the 4Prsquos o the first edition have expanded to the 6Prsquos in the third edition polymer

processing product perormace post-consumer lie and profit In the last 18

years this book has become a reerence or many practicing engineers most o

whom were introduced to the book as students The first and second editions were

praised because o the vast number o graphs and data that can be used as reer-

ences We have urther strengthened this attribute by expanding a comprehensive

table in the appendix that contains material property graphs or several polymers

Furthermore in this edition we added color to the figures and graphs making the

book more appealing to the reader

With this edition we owe our gratitude to Dr Christine Strohm or editing the book

and catching those small typos and inconsistencies in the text and equations Wethank Dr Nadine Warkotsch and Steffen Joerg o Hanser Publishers or their coop-

eration during the production o this book We are grateul to Luz Mayed D

Nouguez and Tobias Mattner or the superb job drawing the figures and to Tobias

Mattner or his suggestions on how to make many o the figures more understand-

able A special thanks to Katerina Saacutenchez or the graphs related to recycling o

plastics in Chapter 1 and to Nora Catalina Restrepo or generating the polymer

statistic graphs in Chapter 2 My graduate students Roberto Monroy Luisa Loacutepez

Tom Mulholland Jakob Onken Camilo Peacuterez Daniel Ramiacuterez Jochen Wellekoetter

and Yuxiao Zhang organized by William Aquite supplied extra problems and solu-

tions or the third edition thank you Special thanks to Diane or ndash as always ndash

serving as a sounding board and advisor during this project

Spring 2012

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

Preface to the

Third Edition

3

Z e i l e n

Uuml b e r s a t z

b i t t e

k uuml r z e n

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Contents

Preface to the First Edition V

Preface to the Third Edition VII

983089 Introduction 983091

983089983089 The 983094 Prsquos 983091

983089983090 General Information 983094

983089983091 Identification of Polymers 983089983091

983089983092 Sustainability ndash The 983094th P 983089983093

References 983090983088

983090 Historical Background 983090983089

983090983089 From Natural to Synthetic Rubber 983090983089

983090983090 Cellulose and the $983089983088983088983088983088 Idea 983090983095

983090983091 Galalith ndash The Milk Stone 983091983088

983090983092 Leo Baekeland and the Plastics Industry 983091983089

983090983093 Herman Mark and the American Polymer Education 983091983092

983090983094 Wallace Hume Carothers and Synthetic Polymers 983091983095

983090983095 Polyethylene ndash A Product of Brain and Brawn 983091983097

983090983096 The Super Fiber and the Woman Who Invented It 983092983090

983090983097 One Last Word ndash Plastics 983092983092

References 983092983095

983091 Structure of Polymers 983092983097

983091983089 Macromolecular Structure of Polymers 983092983097983091983090 Molecular Bonds and Inter-Molecular Attraction 983093983088

983091983091 Molecular Weight 983093983089

7252019 CH-1Material Science of Polymers for Engineers

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X Contents

983091983092 Conformation and Configuration of Polymer Molecules 983093983094

983091983093 Arrangement of Polymer Molecules 983093983097

983091983093983089 Thermoplastic Polymers 983094983088

983091983093983090 Amorphous Thermoplastics 983094983088

983091983093983091 Semi-Crystalline Thermoplastics 983094983090

983091983093983092 Thermosets and Cross-Linked Elastomers 983095983090

983091983094 Copolymers and Polymer Blends 983095983091

983091983095 Polymer Additives 983095983093

983091983095983089 Flame Retardants 983095983093

983091983095983090 Stabilizers 983095983095

983091983095983091 Antistatic Agents 983095983096

983091983095983092 Fillers 983095983096

983091983095983093 Blowing Agents 983095983097

References 983096983090

983092 Thermal Properties of Polymers 983096983091

983092983089 Material Properties 983096983093

983092983089983089 Thermal Conductivity 983096983093

983092983089983090 Specific Heat 983097983089

983092983089983091 Density 983097983091

983092983089983092 Thermal Diffusivity 983097983094 983092983089983093 Linear Coefficient of Thermal Expansion 983097983095

983092983089983094 Thermal Penetration 983097983096

983092983089983095 Glass Transition Temperature 983097983097

983092983089983096 Melting Temperature 983097983097

983092983090 Measuring Thermal Data 983097983097

983092983090983089 Differential Thermal Analysis (DTA) 983089983088983088

983092983090983090 Differential Scanning Calorimeter (DSC) 983089983088983089

983092983090983091 Thermomechanical Analysis (TMA) 983089983088983091 983092983090983092 Thermogravimetry (TGA) 983089983088983092

983092983090983093 Density Measurements 983089983088983093

References 983089983088983097

983093 Rheology of Polymer Melts 983089983089983089

983093983089 Introduction 983089983089983089

983093983089983089 Continuum Mechanics 983089983089983089

983093983089983090 The Generalized Newtonian Fluid 983089983089983091983093983089983091 Normal Stresses in Shear Flow 983089983089983093

983093983089983092 Deborah Number 983089983089983094

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XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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7252019 CH-1Material Science of Polymers for Engineers

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 6: CH-1Material Science of Polymers for Engineers

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VI Preface to the First Edition

are grateul to Richard Theriault or prooreading the entire manuscript We also

thank the ollowing people who helped prooread or gave suggestions during the

preparation o the book Susanne Belovari Bruce A Davis Jeffrey Giacomin Paul J

Gramann Matthew Kaegebein Gwan-Wan Lai Maria del Pilar Noriega E Antoine C

Rios B Linards U Stradins and Ester M Sun Susanne Belovari and Andrea Jung-Mack are acknowledged or translating portions o Werkstoffkunde Kunststoffe rom

German to English We also thank Tara Ruggiero or preparing the camera-ready

manuscript Many o the figures were taken rom class notes o the mechanical engi-

neering senior elective course Engineering Design with Polymers Special thanks

are offered to Lynda Litzkow Philipp Ehrenstein and Bryan Hutchinson or the

superb job o drawing those figures Matthias Mahlke o Bayer AG in Leverkusen

Germany Laura Dietsche Joseph Dooley and Kevin Hughes o Dow Chemical in Mid-

land Michigan and Mauricio DeGrei and Juan Diego Sierra o the ICIPC in Medelliacuten

Colombia are acknowledged or some o the figures Thanks are due to Marcia

Sanders or copy editing the final manuscript We are grateul to Wolgang Glenz

Martha Kuumlrzl Ed Immergut and Carol Radtke o Hanser Publishers or their support

throughout the development o this book Above all the authors thank their wives

or their patience

Summer 1995

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

7252019 CH-1Material Science of Polymers for Engineers

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The first edition o this book was adopted by several universities in North and

South America Europe and Asia as a textbook to introduce engineering students

to the materials science o polymers The book was also translated into Japanese in

1998 Korean in 1999 and Spanish in 2008 The proessors who taught with thefirst and second editions as well as their students liked the unified approach we

took The changes and additions that were introduced in this edition are based on

suggestions rom these proessors and their students as well as rom our own

experience using it as a class textbook

Afer two revisions and two decades o teaching it has become clear that sustaina-

bility and profits are important when dealing with polymeric materials Thereore

the 4Prsquos o the first edition have expanded to the 6Prsquos in the third edition polymer

processing product perormace post-consumer lie and profit In the last 18

years this book has become a reerence or many practicing engineers most o

whom were introduced to the book as students The first and second editions were

praised because o the vast number o graphs and data that can be used as reer-

ences We have urther strengthened this attribute by expanding a comprehensive

table in the appendix that contains material property graphs or several polymers

Furthermore in this edition we added color to the figures and graphs making the

book more appealing to the reader

With this edition we owe our gratitude to Dr Christine Strohm or editing the book

and catching those small typos and inconsistencies in the text and equations Wethank Dr Nadine Warkotsch and Steffen Joerg o Hanser Publishers or their coop-

eration during the production o this book We are grateul to Luz Mayed D

Nouguez and Tobias Mattner or the superb job drawing the figures and to Tobias

Mattner or his suggestions on how to make many o the figures more understand-

able A special thanks to Katerina Saacutenchez or the graphs related to recycling o

plastics in Chapter 1 and to Nora Catalina Restrepo or generating the polymer

statistic graphs in Chapter 2 My graduate students Roberto Monroy Luisa Loacutepez

Tom Mulholland Jakob Onken Camilo Peacuterez Daniel Ramiacuterez Jochen Wellekoetter

and Yuxiao Zhang organized by William Aquite supplied extra problems and solu-

tions or the third edition thank you Special thanks to Diane or ndash as always ndash

serving as a sounding board and advisor during this project

Spring 2012

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

Preface to the

Third Edition

3

Z e i l e n

Uuml b e r s a t z

b i t t e

k uuml r z e n

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7252019 CH-1Material Science of Polymers for Engineers

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Contents

Preface to the First Edition V

Preface to the Third Edition VII

983089 Introduction 983091

983089983089 The 983094 Prsquos 983091

983089983090 General Information 983094

983089983091 Identification of Polymers 983089983091

983089983092 Sustainability ndash The 983094th P 983089983093

References 983090983088

983090 Historical Background 983090983089

983090983089 From Natural to Synthetic Rubber 983090983089

983090983090 Cellulose and the $983089983088983088983088983088 Idea 983090983095

983090983091 Galalith ndash The Milk Stone 983091983088

983090983092 Leo Baekeland and the Plastics Industry 983091983089

983090983093 Herman Mark and the American Polymer Education 983091983092

983090983094 Wallace Hume Carothers and Synthetic Polymers 983091983095

983090983095 Polyethylene ndash A Product of Brain and Brawn 983091983097

983090983096 The Super Fiber and the Woman Who Invented It 983092983090

983090983097 One Last Word ndash Plastics 983092983092

References 983092983095

983091 Structure of Polymers 983092983097

983091983089 Macromolecular Structure of Polymers 983092983097983091983090 Molecular Bonds and Inter-Molecular Attraction 983093983088

983091983091 Molecular Weight 983093983089

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X Contents

983091983092 Conformation and Configuration of Polymer Molecules 983093983094

983091983093 Arrangement of Polymer Molecules 983093983097

983091983093983089 Thermoplastic Polymers 983094983088

983091983093983090 Amorphous Thermoplastics 983094983088

983091983093983091 Semi-Crystalline Thermoplastics 983094983090

983091983093983092 Thermosets and Cross-Linked Elastomers 983095983090

983091983094 Copolymers and Polymer Blends 983095983091

983091983095 Polymer Additives 983095983093

983091983095983089 Flame Retardants 983095983093

983091983095983090 Stabilizers 983095983095

983091983095983091 Antistatic Agents 983095983096

983091983095983092 Fillers 983095983096

983091983095983093 Blowing Agents 983095983097

References 983096983090

983092 Thermal Properties of Polymers 983096983091

983092983089 Material Properties 983096983093

983092983089983089 Thermal Conductivity 983096983093

983092983089983090 Specific Heat 983097983089

983092983089983091 Density 983097983091

983092983089983092 Thermal Diffusivity 983097983094 983092983089983093 Linear Coefficient of Thermal Expansion 983097983095

983092983089983094 Thermal Penetration 983097983096

983092983089983095 Glass Transition Temperature 983097983097

983092983089983096 Melting Temperature 983097983097

983092983090 Measuring Thermal Data 983097983097

983092983090983089 Differential Thermal Analysis (DTA) 983089983088983088

983092983090983090 Differential Scanning Calorimeter (DSC) 983089983088983089

983092983090983091 Thermomechanical Analysis (TMA) 983089983088983091 983092983090983092 Thermogravimetry (TGA) 983089983088983092

983092983090983093 Density Measurements 983089983088983093

References 983089983088983097

983093 Rheology of Polymer Melts 983089983089983089

983093983089 Introduction 983089983089983089

983093983089983089 Continuum Mechanics 983089983089983089

983093983089983090 The Generalized Newtonian Fluid 983089983089983091983093983089983091 Normal Stresses in Shear Flow 983089983089983093

983093983089983092 Deborah Number 983089983089983094

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XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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7252019 CH-1Material Science of Polymers for Engineers

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 7: CH-1Material Science of Polymers for Engineers

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The first edition o this book was adopted by several universities in North and

South America Europe and Asia as a textbook to introduce engineering students

to the materials science o polymers The book was also translated into Japanese in

1998 Korean in 1999 and Spanish in 2008 The proessors who taught with thefirst and second editions as well as their students liked the unified approach we

took The changes and additions that were introduced in this edition are based on

suggestions rom these proessors and their students as well as rom our own

experience using it as a class textbook

Afer two revisions and two decades o teaching it has become clear that sustaina-

bility and profits are important when dealing with polymeric materials Thereore

the 4Prsquos o the first edition have expanded to the 6Prsquos in the third edition polymer

processing product perormace post-consumer lie and profit In the last 18

years this book has become a reerence or many practicing engineers most o

whom were introduced to the book as students The first and second editions were

praised because o the vast number o graphs and data that can be used as reer-

ences We have urther strengthened this attribute by expanding a comprehensive

table in the appendix that contains material property graphs or several polymers

Furthermore in this edition we added color to the figures and graphs making the

book more appealing to the reader

With this edition we owe our gratitude to Dr Christine Strohm or editing the book

and catching those small typos and inconsistencies in the text and equations Wethank Dr Nadine Warkotsch and Steffen Joerg o Hanser Publishers or their coop-

eration during the production o this book We are grateul to Luz Mayed D

Nouguez and Tobias Mattner or the superb job drawing the figures and to Tobias

Mattner or his suggestions on how to make many o the figures more understand-

able A special thanks to Katerina Saacutenchez or the graphs related to recycling o

plastics in Chapter 1 and to Nora Catalina Restrepo or generating the polymer

statistic graphs in Chapter 2 My graduate students Roberto Monroy Luisa Loacutepez

Tom Mulholland Jakob Onken Camilo Peacuterez Daniel Ramiacuterez Jochen Wellekoetter

and Yuxiao Zhang organized by William Aquite supplied extra problems and solu-

tions or the third edition thank you Special thanks to Diane or ndash as always ndash

serving as a sounding board and advisor during this project

Spring 2012

Tim A Osswald Georg Menges

Madison Wisconsin USA Aachen Germany

Preface to the

Third Edition

3

Z e i l e n

Uuml b e r s a t z

b i t t e

k uuml r z e n

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Contents

Preface to the First Edition V

Preface to the Third Edition VII

983089 Introduction 983091

983089983089 The 983094 Prsquos 983091

983089983090 General Information 983094

983089983091 Identification of Polymers 983089983091

983089983092 Sustainability ndash The 983094th P 983089983093

References 983090983088

983090 Historical Background 983090983089

983090983089 From Natural to Synthetic Rubber 983090983089

983090983090 Cellulose and the $983089983088983088983088983088 Idea 983090983095

983090983091 Galalith ndash The Milk Stone 983091983088

983090983092 Leo Baekeland and the Plastics Industry 983091983089

983090983093 Herman Mark and the American Polymer Education 983091983092

983090983094 Wallace Hume Carothers and Synthetic Polymers 983091983095

983090983095 Polyethylene ndash A Product of Brain and Brawn 983091983097

983090983096 The Super Fiber and the Woman Who Invented It 983092983090

983090983097 One Last Word ndash Plastics 983092983092

References 983092983095

983091 Structure of Polymers 983092983097

983091983089 Macromolecular Structure of Polymers 983092983097983091983090 Molecular Bonds and Inter-Molecular Attraction 983093983088

983091983091 Molecular Weight 983093983089

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X Contents

983091983092 Conformation and Configuration of Polymer Molecules 983093983094

983091983093 Arrangement of Polymer Molecules 983093983097

983091983093983089 Thermoplastic Polymers 983094983088

983091983093983090 Amorphous Thermoplastics 983094983088

983091983093983091 Semi-Crystalline Thermoplastics 983094983090

983091983093983092 Thermosets and Cross-Linked Elastomers 983095983090

983091983094 Copolymers and Polymer Blends 983095983091

983091983095 Polymer Additives 983095983093

983091983095983089 Flame Retardants 983095983093

983091983095983090 Stabilizers 983095983095

983091983095983091 Antistatic Agents 983095983096

983091983095983092 Fillers 983095983096

983091983095983093 Blowing Agents 983095983097

References 983096983090

983092 Thermal Properties of Polymers 983096983091

983092983089 Material Properties 983096983093

983092983089983089 Thermal Conductivity 983096983093

983092983089983090 Specific Heat 983097983089

983092983089983091 Density 983097983091

983092983089983092 Thermal Diffusivity 983097983094 983092983089983093 Linear Coefficient of Thermal Expansion 983097983095

983092983089983094 Thermal Penetration 983097983096

983092983089983095 Glass Transition Temperature 983097983097

983092983089983096 Melting Temperature 983097983097

983092983090 Measuring Thermal Data 983097983097

983092983090983089 Differential Thermal Analysis (DTA) 983089983088983088

983092983090983090 Differential Scanning Calorimeter (DSC) 983089983088983089

983092983090983091 Thermomechanical Analysis (TMA) 983089983088983091 983092983090983092 Thermogravimetry (TGA) 983089983088983092

983092983090983093 Density Measurements 983089983088983093

References 983089983088983097

983093 Rheology of Polymer Melts 983089983089983089

983093983089 Introduction 983089983089983089

983093983089983089 Continuum Mechanics 983089983089983089

983093983089983090 The Generalized Newtonian Fluid 983089983089983091983093983089983091 Normal Stresses in Shear Flow 983089983089983093

983093983089983092 Deborah Number 983089983089983094

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XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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7252019 CH-1Material Science of Polymers for Engineers

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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7252019 CH-1Material Science of Polymers for Engineers

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 8: CH-1Material Science of Polymers for Engineers

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Contents

Preface to the First Edition V

Preface to the Third Edition VII

983089 Introduction 983091

983089983089 The 983094 Prsquos 983091

983089983090 General Information 983094

983089983091 Identification of Polymers 983089983091

983089983092 Sustainability ndash The 983094th P 983089983093

References 983090983088

983090 Historical Background 983090983089

983090983089 From Natural to Synthetic Rubber 983090983089

983090983090 Cellulose and the $983089983088983088983088983088 Idea 983090983095

983090983091 Galalith ndash The Milk Stone 983091983088

983090983092 Leo Baekeland and the Plastics Industry 983091983089

983090983093 Herman Mark and the American Polymer Education 983091983092

983090983094 Wallace Hume Carothers and Synthetic Polymers 983091983095

983090983095 Polyethylene ndash A Product of Brain and Brawn 983091983097

983090983096 The Super Fiber and the Woman Who Invented It 983092983090

983090983097 One Last Word ndash Plastics 983092983092

References 983092983095

983091 Structure of Polymers 983092983097

983091983089 Macromolecular Structure of Polymers 983092983097983091983090 Molecular Bonds and Inter-Molecular Attraction 983093983088

983091983091 Molecular Weight 983093983089

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X Contents

983091983092 Conformation and Configuration of Polymer Molecules 983093983094

983091983093 Arrangement of Polymer Molecules 983093983097

983091983093983089 Thermoplastic Polymers 983094983088

983091983093983090 Amorphous Thermoplastics 983094983088

983091983093983091 Semi-Crystalline Thermoplastics 983094983090

983091983093983092 Thermosets and Cross-Linked Elastomers 983095983090

983091983094 Copolymers and Polymer Blends 983095983091

983091983095 Polymer Additives 983095983093

983091983095983089 Flame Retardants 983095983093

983091983095983090 Stabilizers 983095983095

983091983095983091 Antistatic Agents 983095983096

983091983095983092 Fillers 983095983096

983091983095983093 Blowing Agents 983095983097

References 983096983090

983092 Thermal Properties of Polymers 983096983091

983092983089 Material Properties 983096983093

983092983089983089 Thermal Conductivity 983096983093

983092983089983090 Specific Heat 983097983089

983092983089983091 Density 983097983091

983092983089983092 Thermal Diffusivity 983097983094 983092983089983093 Linear Coefficient of Thermal Expansion 983097983095

983092983089983094 Thermal Penetration 983097983096

983092983089983095 Glass Transition Temperature 983097983097

983092983089983096 Melting Temperature 983097983097

983092983090 Measuring Thermal Data 983097983097

983092983090983089 Differential Thermal Analysis (DTA) 983089983088983088

983092983090983090 Differential Scanning Calorimeter (DSC) 983089983088983089

983092983090983091 Thermomechanical Analysis (TMA) 983089983088983091 983092983090983092 Thermogravimetry (TGA) 983089983088983092

983092983090983093 Density Measurements 983089983088983093

References 983089983088983097

983093 Rheology of Polymer Melts 983089983089983089

983093983089 Introduction 983089983089983089

983093983089983089 Continuum Mechanics 983089983089983089

983093983089983090 The Generalized Newtonian Fluid 983089983089983091983093983089983091 Normal Stresses in Shear Flow 983089983089983093

983093983089983092 Deborah Number 983089983089983094

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XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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7252019 CH-1Material Science of Polymers for Engineers

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 9: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

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Contents

Preface to the First Edition V

Preface to the Third Edition VII

983089 Introduction 983091

983089983089 The 983094 Prsquos 983091

983089983090 General Information 983094

983089983091 Identification of Polymers 983089983091

983089983092 Sustainability ndash The 983094th P 983089983093

References 983090983088

983090 Historical Background 983090983089

983090983089 From Natural to Synthetic Rubber 983090983089

983090983090 Cellulose and the $983089983088983088983088983088 Idea 983090983095

983090983091 Galalith ndash The Milk Stone 983091983088

983090983092 Leo Baekeland and the Plastics Industry 983091983089

983090983093 Herman Mark and the American Polymer Education 983091983092

983090983094 Wallace Hume Carothers and Synthetic Polymers 983091983095

983090983095 Polyethylene ndash A Product of Brain and Brawn 983091983097

983090983096 The Super Fiber and the Woman Who Invented It 983092983090

983090983097 One Last Word ndash Plastics 983092983092

References 983092983095

983091 Structure of Polymers 983092983097

983091983089 Macromolecular Structure of Polymers 983092983097983091983090 Molecular Bonds and Inter-Molecular Attraction 983093983088

983091983091 Molecular Weight 983093983089

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 1038

X Contents

983091983092 Conformation and Configuration of Polymer Molecules 983093983094

983091983093 Arrangement of Polymer Molecules 983093983097

983091983093983089 Thermoplastic Polymers 983094983088

983091983093983090 Amorphous Thermoplastics 983094983088

983091983093983091 Semi-Crystalline Thermoplastics 983094983090

983091983093983092 Thermosets and Cross-Linked Elastomers 983095983090

983091983094 Copolymers and Polymer Blends 983095983091

983091983095 Polymer Additives 983095983093

983091983095983089 Flame Retardants 983095983093

983091983095983090 Stabilizers 983095983095

983091983095983091 Antistatic Agents 983095983096

983091983095983092 Fillers 983095983096

983091983095983093 Blowing Agents 983095983097

References 983096983090

983092 Thermal Properties of Polymers 983096983091

983092983089 Material Properties 983096983093

983092983089983089 Thermal Conductivity 983096983093

983092983089983090 Specific Heat 983097983089

983092983089983091 Density 983097983091

983092983089983092 Thermal Diffusivity 983097983094 983092983089983093 Linear Coefficient of Thermal Expansion 983097983095

983092983089983094 Thermal Penetration 983097983096

983092983089983095 Glass Transition Temperature 983097983097

983092983089983096 Melting Temperature 983097983097

983092983090 Measuring Thermal Data 983097983097

983092983090983089 Differential Thermal Analysis (DTA) 983089983088983088

983092983090983090 Differential Scanning Calorimeter (DSC) 983089983088983089

983092983090983091 Thermomechanical Analysis (TMA) 983089983088983091 983092983090983092 Thermogravimetry (TGA) 983089983088983092

983092983090983093 Density Measurements 983089983088983093

References 983089983088983097

983093 Rheology of Polymer Melts 983089983089983089

983093983089 Introduction 983089983089983089

983093983089983089 Continuum Mechanics 983089983089983089

983093983089983090 The Generalized Newtonian Fluid 983089983089983091983093983089983091 Normal Stresses in Shear Flow 983089983089983093

983093983089983092 Deborah Number 983089983089983094

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7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 1238

XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

7252019 CH-1Material Science of Polymers for Engineers

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

7252019 CH-1Material Science of Polymers for Engineers

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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7252019 CH-1Material Science of Polymers for Engineers

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PART 983089Basic Principles

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7252019 CH-1Material Science of Polymers for Engineers

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2238

983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

7252019 CH-1Material Science of Polymers for Engineers

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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7252019 CH-1Material Science of Polymers for Engineers

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 10: CH-1Material Science of Polymers for Engineers

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X Contents

983091983092 Conformation and Configuration of Polymer Molecules 983093983094

983091983093 Arrangement of Polymer Molecules 983093983097

983091983093983089 Thermoplastic Polymers 983094983088

983091983093983090 Amorphous Thermoplastics 983094983088

983091983093983091 Semi-Crystalline Thermoplastics 983094983090

983091983093983092 Thermosets and Cross-Linked Elastomers 983095983090

983091983094 Copolymers and Polymer Blends 983095983091

983091983095 Polymer Additives 983095983093

983091983095983089 Flame Retardants 983095983093

983091983095983090 Stabilizers 983095983095

983091983095983091 Antistatic Agents 983095983096

983091983095983092 Fillers 983095983096

983091983095983093 Blowing Agents 983095983097

References 983096983090

983092 Thermal Properties of Polymers 983096983091

983092983089 Material Properties 983096983093

983092983089983089 Thermal Conductivity 983096983093

983092983089983090 Specific Heat 983097983089

983092983089983091 Density 983097983091

983092983089983092 Thermal Diffusivity 983097983094 983092983089983093 Linear Coefficient of Thermal Expansion 983097983095

983092983089983094 Thermal Penetration 983097983096

983092983089983095 Glass Transition Temperature 983097983097

983092983089983096 Melting Temperature 983097983097

983092983090 Measuring Thermal Data 983097983097

983092983090983089 Differential Thermal Analysis (DTA) 983089983088983088

983092983090983090 Differential Scanning Calorimeter (DSC) 983089983088983089

983092983090983091 Thermomechanical Analysis (TMA) 983089983088983091 983092983090983092 Thermogravimetry (TGA) 983089983088983092

983092983090983093 Density Measurements 983089983088983093

References 983089983088983097

983093 Rheology of Polymer Melts 983089983089983089

983093983089 Introduction 983089983089983089

983093983089983089 Continuum Mechanics 983089983089983089

983093983089983090 The Generalized Newtonian Fluid 983089983089983091983093983089983091 Normal Stresses in Shear Flow 983089983089983093

983093983089983092 Deborah Number 983089983089983094

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

7252019 CH-1Material Science of Polymers for Engineers

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

7252019 CH-1Material Science of Polymers for Engineers

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

7252019 CH-1Material Science of Polymers for Engineers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

7252019 CH-1Material Science of Polymers for Engineers

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 11: CH-1Material Science of Polymers for Engineers

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XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

7252019 CH-1Material Science of Polymers for Engineers

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3238

983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3338

983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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7252019 CH-1Material Science of Polymers for Engineers

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 12: CH-1Material Science of Polymers for Engineers

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XII Contents

983094983090983090 Dispersive Mixing 983089983096983092

983094983090983090983089 Break-Up of Particulate Agglomerates 983089983096983092

983094983090983090983090 Break-Up of Fluid Droplets 983089983096983094

983094983090983091 Mixing Devices 983089983096983097

983094983090983091983089 Static Mixers 983089983097983088983094983090983091983090 Banbury Mixer 983089983097983088

983094983090983091983091 Mixing in Single Screw Extruders 983089983097983090

983094983090983091983092 Co-Kneader 983089983097983092

983094983090983091983093 Twin Screw Extruders 983089983097983093

983094983090983092 Energy Consumption During Mixing 983089983097983096

983094983090983093 Mixing Quality and Efficiency 983089983097983097

983094983090983094 Plasticization 983090983088983089

983094983091 Injection Molding 983090983088983094983094983091983089 The Injection Molding Cycle 983090983088983095

983094983091983090 The Injection Molding Machine 983090983089983088

983094983091983090983089 The Plasticating and Injection Unit 983090983089983088

983094983091983090983090 The Clamping Unit 983090983089983089

983094983091983090983091 The Mold Cavity 983090983089983091

983094983092 Special Injection Molding Processes 983090983089983094

983094983092983089 Multi-Component Injection Molding 983090983089983094

983094983092983090 Co-Injection Molding 983090983089983096

983094983092983091 Gas-Assisted Injection Molding (GAIM) 983090983089983097983094983092983092 Injection-Compression Molding 983090983090983089

983094983092983093 Reaction Injection Molding (RIM) 983090983090983090

983094983092983094 Liquid Silicone Rubber Injection Molding 983090983090983093

983094983093 Secondary Shaping 983090983090983094

983094983093983089 Fiber Spinning 983090983090983094

983094983093983090 Film Production 983090983090983095

983094983093983090983089 Cast Film Extrusion 983090983090983095

983094983093983090983090 Film Blowing 983090983090983096983094983093983091 Blow Molding 983090983091983088

983094983093983091983089 Extrusion Blow Molding 983090983091983088

983094983093983091983090 Injection Blow Molding 983090983091983090

983094983093983091983091 Thermoforming 983090983091983091

983094983094 Calendering 983090983091983093

983094983095 Coating 983090983091983096

983094983096 Compression Molding 983090983092983088

983094983097 Foaming 983090983092983090

983094983089983088 Rotational Molding 983090983092983092

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 1538

983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

7252019 CH-1Material Science of Polymers for Engineers

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 1938

PART 983089Basic Principles

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2038

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2138

1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 13: CH-1Material Science of Polymers for Engineers

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983094983089983089 Computer Simulation in Polymer Processing 983090983092983093

983094983089983089983089 Mold Filling Simulation 983090983092983094

983094983089983089983090 Orientation Predictions 983090983092983096

983094983089983089983091 Shrinkage and Warpage Predictions 983090983092983097

References 983090983094983088

983095 Anisotropy Development During Processing 983090983094983091

983095983089 Orientation in the Final Part 983090983094983091

983095983089983089 Processing Thermoplastic Polymers 983090983094983091

983095983089983090 Processing Thermoset Polymers 983090983095983089

983095983090 Predicting Orientation in the Final Part 983090983095983093

983095983090983089 Planar Orientation Distribution Function 983090983095983094

983095983090983090 Single Particle Motion 983090983095983096 983095983090983091 Jefferyrsquos Model 983090983095983097

983095983090983092 Folgar-Tucker Model 983090983096983088

983095983090983093 Tensor Representation of Fiber Orientation 983090983096983089

983095983090983093983089 Predicting Orientation in Complex Parts Using

Computer Simulation 983090983096983090

983095983091 Fiber Damage 983090983096983095

References 983090983097983091

983096 Solidification of Polymers 983090983097983093

983096983089 Solidification of Thermoplastics 983090983097983093

983096983089983089 Thermodynamics During Cooling 983090983097983093

983096983089983090 Morphological Structure 983090983097983097

983096983089983091 Crystallization 983091983088983088

983096983089983092 Heat Transfer During Solidification 983091983088983091

983096983090 Solidification of Thermosets 983091983088983095

983096983090983089 Curing Reaction 983091983088983096983096983090983090 Cure Kinetics 983091983088983097

983096983090983091 Heat Transfer During Cure 983091983089983092

983096983091 Residual Stresses and Warpage of Polymeric Parts 983091983089983094

983096983091983089 Residual Stress Models 983091983089983097

983096983091983089983089 Residual Stress Model Without Phase Change Effects 983091983090983089

983096983091983089983090 Model to Predict Residual Stresses with

Phase Change Effects 983091983090983090

983096983091983090 Other Simple Models to Predict Residual Stresses and Warpage 983091983090983092983096983091983090983089 Uneven Mold Temperature 983091983090983094

983096983091983090983090 Residual Stress in a Thin Thermoset Part 983091983090983095

983096983091983090983091 Anisotropy Induced Curvature Change 983091983090983096

Contents XIII

7252019 CH-1Material Science of Polymers for Engineers

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 1538

983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

7252019 CH-1Material Science of Polymers for Engineers

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

7252019 CH-1Material Science of Polymers for Engineers

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

7252019 CH-1Material Science of Polymers for Engineers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

7252019 CH-1Material Science of Polymers for Engineers

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 14: CH-1Material Science of Polymers for Engineers

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XIV Contents

983096983091983091 Predicting Warpage in Actual Parts 983091983090983097

References 983091983091983094

983097 Mechanical Behavior of Polymers 983091983092983089

983097983089 Basic Concepts of Stress and Strain 983091983092983089

983097983089983089 Plane Stress 983091983092983090

983097983089983090 Plane Strain 983091983092983091

983097983090 Viscoelastic Behavior of Polymers 983091983092983091

983097983090983089 Stress Relaxation Test 983091983092983092

983097983090983090 Time-Temperature Superposition (WLF-Equation) 983091983092983094

983097983090983091 The Boltzmann Superposition Principle 983091983092983095

983097983091 Applying Linear Viscoelasticity to Describe the Behavior of Polymers 983091983092983096

983097983091983089 The Maxwell Model 983091983092983097

983097983091983090 Kelvin Model 983091983093983088

983097983091983091 Jeffrey Model 983091983093983090

983097983091983092 Standard Linear Solid Model 983091983093983092

983097983091983093 The Generalized Maxwell Model 983091983093983094

983097983092 The Short-Term Tensile Test 983091983094983089

983097983092983089 Rubber Elasticity 983091983094983090

983097983092983090 The Tensile Test and Thermoplastic Polymers 983091983094983095

983097983093 Creep Test 983091983095983092

983097983093983089 Isochronous and Isometric Creep Plots 983091983095983096

983097983094 Dynamic Mechanical Tests 983091983095983097

983097983094983089 Torsion Pendulum 983091983095983097

983097983094983090 Sinusoidal Oscillatory Test 983091983096983091

983097983095 Effects of Structure and Composition on Mechanical Properties 983091983096983093

983097983095983089 Amorphous Thermoplastics 983091983096983093

983097983095983090 Semi-Crystalline Thermoplastics 983091983096983096

983097983095983091 Oriented Thermoplastics 983091983097983088983097983095983092 Crosslinked Polymers 983091983097983093

983097983096 Mechanical Behavior of Filled and Reinforced Polymers 983091983097983095

983097983096983089 Anisotropic Strain-Stress Relation 983091983097983097

983097983096983090 Aligned Fiber Reinforced Composite Laminates 983092983088983088

983097983096983091 Transformation of Fiber Reinforced Composite Laminate

Properties 983092983088983090

983097983096983092 Reinforced Composite Laminates with a Fiber Orientation

Distribution Function 983092983088983092983097983097 Strength Stability Under Heat 983092983088983093

References 983092983090983089

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 15: CH-1Material Science of Polymers for Engineers

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983089983088 Failure and Damage of Polymers 983092983090983091

983089983088983089 Fracture Mechanics 983092983090983091

983089983088983089983089 Fracture Predictions Based on the Stress Intensity Factor 983092983090983092

983089983088983089983090 Fracture Predictions Based on an Energy Balance 983092983090983094

983089983088983089983091 Linear Viscoelastic Fracture Predictions Based on J -Integrals 983092983090983096

983089983088983090 Short-Term Tensile Strength 983092983091983088

983089983088983090983089 Brittle Failure 983092983091983088

983089983088983090983090 Ductile Failure 983092983091983092

983089983088983090983091 Failure of Highly Filled Systems or Composites 983092983091983095

983089983088983091 Impact Strength 983092983092983088

983089983088983091983089 Impact Test Methods 983092983092983094

983089983088983091983090 Fracture Mechanics Analysis of Impact Failure 983092983093983088

983089983088983092 Creep Rupture 983092983093983093

983089983088983092983089 Creep Rupture Tests 983092983093983094

983089983088983092983090 Fracture Mechanics Analysis of Creep Rupture 983092983093983097

983089983088983093 Fatigue 983092983093983097

983089983088983093983089 Fatigue Test Methods 983092983094983088

983089983088983093983090 Fracture Mechanics Analysis of Fatigue Failure 983092983094983096

983089983088983094 Friction and Wear 983092983095983088

983089983088983095 Stability of Polymer Structures 983092983095983091983089983088983096 Environmental Effects on Polymer Failure 983092983095983093

983089983088983096983089 Weathering 983092983095983093

983089983088983096983090 Chemical Degradation 983092983096983088

983089983088983096983091 Thermal Degradation of Polymers 983092983096983090

References 983092983096983094

983089983089 Electrical Properties of Polymers 983092983096983097

983089983089983089 Dielectric Behavior 983092983096983097983089983089983089983089 Dielectric Coefficient 983092983096983097

983089983089983089983090 Mechanisms of Dielectrical Polarization 983092983097983091

983089983089983089983091 Dielectric Dissipation Factor 983092983097983094

983089983089983089983092 Implications of Electrical and Thermal Loss in a Dielectric 983092983097983097

983089983089983090 Electric Conductivity 983093983088983088

983089983089983090983089 Electric Resistance 983093983088983088

983089983089983090983090 Physical Causes of Volume Conductivity 983093983088983089

983089983089983091 Application Problems 983093983088983092983089983089983091983089 Electric Breakdown 983093983088983092

983089983089983091983090 Electrostatic Charge 983093983088983096

Contents XV

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 16: CH-1Material Science of Polymers for Engineers

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XVI Contents

983089983089983091983091 Electrets 983093983088983097

983089983089983091983092 Electromagnetic Interference Shielding (EMI Shielding) 983093983088983097

983089983089983092 Magnetic Properties 983093983089983088

983089983089983092983089 Magnetizability 983093983089983088

983089983089983092983090 Magnetic Resonance 983093983089983088

References 983093983089983089

983089983090 Optical Properties of Polymers 983093983089983091

983089983090983089 Index of Refraction 983093983089983091

983089983090983090 Photoelasticity and Birefringence 983093983089983094

983089983090983091 Transparency Reflection Absorption and Transmittance 983093983090983088

983089983090983092 Gloss 983093983090983094983089983090983093 Color 983093983090983095

983089983090983094 Infrared Spectroscopy 983093983091983089

983089983090983095 Infrared Pyrometry 983093983091983090

983089983090983096 Heating with Infrared Radiation 983093983091983092

References 983093983091983094

983089983091 Permeability Properties of Polymers 983093983091983095 983089983091983089 Sorption 983093983091983095

983089983091983090 Diffusion and Permeation 983093983091983097

983089983091983091 Measuring S D and P 983093983092983092

983089983091983092 Corrosion of Polymers and Cracking [983093] 983093983092983093

983089983091983093 Diffusion of Polymer Molecules and Self-diffusion 983093983092983096

References 983093983092983096

983089983092 Acoustic Properties of Polymers 983093983092983097

983089983092983089 Speed of Sound 983093983092983097

983089983092983090 Sound Reflection 983093983093983089

983089983092983091 Sound Absorption 983093983093983090

References 983093983093983091

Appendix 983093983093983093

Appendix I 983093983093983094

Appendix II 983093983094983092

Appendix III 983093983094983093

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 17: CH-1Material Science of Polymers for Engineers

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Appendix IV ndash Balance Equations 983093983096983091

Continuity Equation 983093983096983091

Energy Equation for a Newtonian Fluid 983093983096983091

Momentum Balance 983093983096983092

Momentum Equation in Terms of τ 983093983096983092Navier-Stokes Equation 983093983096983092

Index 983093983096983095

Contents XVII

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httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 1938

PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

7252019 CH-1Material Science of Polymers for Engineers

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

7252019 CH-1Material Science of Polymers for Engineers

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 18: CH-1Material Science of Polymers for Engineers

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PART 983089Basic Principles

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2138

1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

7252019 CH-1Material Science of Polymers for Engineers

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

7252019 CH-1Material Science of Polymers for Engineers

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

7252019 CH-1Material Science of Polymers for Engineers

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 19: CH-1Material Science of Polymers for Engineers

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PART 983089Basic Principles

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 20: CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 21: CH-1Material Science of Polymers for Engineers

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1As the word itsel suggests polymers1 are materials composed o many molecules

or parts that result in long chains These large molecules are generally reerred to

as macromolecules The unique material properties o polymers and the versatility

o their processing methods are attributed to their molecular structure For many

applications the ease with which polymers and plastics 2 are processed makes

them the most sought-afer material today Because o their relatively low density

and their ability to be shaped and molded at relatively low temperatures compared

to traditional materials such as metals plastics and polymers are the material o

choice when integrating several parts into a single component ndash a design aspect

usually called part consolidation In act parts and components that have tra-

ditionally been made o wood metal ceramic or glass are redesigned or plastics

on a daily basisHowever the properties o a finished product depend not only on the choice o

material and additives but also on the process used to manuacture the part The

relation that exists between the material and product perormance is reerred to as

the 6 Prsquos Polymer Process Product Performance Post-consumer Life and Profit

This approach and philosophy is used throughout this book

11 The 6 Prsquos

As a result o years o experience in plastics engineering a technique has emerged

that the authors ofen reer to as the 6 Prsquos Basically this approach which is used

throughout this book states that when addressing any one particular o the 6 Prsquos

all other Prsquos must be taken into account To design a product exhibiting a desired

performance at a specific cost (profit) the material (plastic) and the manuacturing

1 From the Greek poli which means many andmeros which means parts

2 The term ldquoplasticsrdquo describes a compound o polymers and various additives fillers and reinorcing

agents

Introduction

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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7252019 CH-1Material Science of Polymers for Engineers

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

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httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 22: CH-1Material Science of Polymers for Engineers

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983092 1 Introduction

technique (process) as well as sustainability issues (post-consumer life) must be

considered The 6 Prsquos is a way to uniy polymer or plastics engineering not only

or students in the classroom but also or practicing engineers and researchers

Figure 11 presents a summary o the 6 Prsquos Each o the 6 Prsquos can be described

individually

Plastic Plastic signifies the molecule the material used and additives such as

fillers fibers pigments mold release agents to name a ew

Process The process can be extrusion injection molding compression molding

or any other process during which the polymeric material is heated melted

mixed pumped shaped and solidified As a result o the thermal history and the

deormation the material in the final part will exhibit a certain morphology a

molecular or filler orientation and even a certain level o degradation that may

influence the properties o the material in the product Product The product can be a pellet a film a fiber a component or an assembly

Performance The product needs to ulfill certain requirements such as with-

standing a thermal load exhibiting specific mechanical properties or having a

certain optical quality to name a ew Furthermore all this may be required in

an environment that can be damaging to the plastic product

Polymer

Post-consumer Life

Performance

Product

Process

MoleculeFillersFibersAdditives

ExtrusionInjectionCompression

CompatibilityAdhesionRegulationLegislation

Properties of polymerProperties of fiberProperties of additives

HeatingMixingPumpingForming

MorphologyOrientationDegradation

PelletFilmFiberComponentAssembly

ThermalMechanicalOpticalEnvironmental

RecyclingEnvironment

SustainabilityRegulationLegislation

Profit

Material costDie and mold costMachine and energy costLabor and automation cost

Figure 11 The 6 Prsquos

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

7252019 CH-1Material Science of Polymers for Engineers

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 23: CH-1Material Science of Polymers for Engineers

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983089983089 The 983094 Prsquos 983093

Profit The success o any product or project is measured by how this product

contributes to the bottom line profits The cost o a product is one o many ac-

tors determining the success o a product It depends on material costs mold and

die costs machine costs and labor costs decisions about automation versus

labor play a significant role

Post-consumer life and Sustainability Today post-consumer lie is primarily

concerned with recycling However issues such as environmental impact and

sustainability should be in every engineerrsquos mind when designing a plastic

product or developing a material to manuacture the product Furthermore engi-

neers should always stay one step ahead o legislation and government regula-

tions regarding products materials and additives

Figure 12 is an illustrative example o how the 6 Prsquos are interrelated within a

single design It depicts an assembly injection molded saety gear clutch where aninner gear is injection molded first and then overmolded with an outer gear The

outer gear shrinks over the inner gear generating sufficient residual hoop stress

to orce the two gears together The combination o the hoop stress between the

gears and the coefficient o riction between the two materials used to mold the

gears results in a maximum torque that the two gears can be subjected to beore

they start sliding past each other One application or such a system is the saety

device or side mirrors in an automobile that allows them to rotate beore breaking

Polymer

Post-consumer Life Performance

Product

(1) Flow

(3) Heat transfer(5) Fiber orientation

(6) Fiber damage

(7) Degradation

(2) Rheological properties

(4) Thermal properties(10) Mechanical properties

(14) Friction coefficients

(12) Assembly(13) Functionality

(15) Disassembly

(16) Choice of materials(17) Regulations and legislation

(8) Anisotropy

(9) Mechanical behavior

(11) Stresses

Process

Profit(18) Material cost

(19) Mold cost(20) Machine cost

(21) Energy cost(22) Value of recycled material

Figure 12 The 6 Prsquos and an assembly injection molded clutch gear (Courtesy Institute or

Plastics Technology (LKT) University o Erlangen-Nuremberg)

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 24: CH-1Material Science of Polymers for Engineers

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983094 1 Introduction

Figure 12 presents a filled mold (right) and a short shot (lef) The short shot shows

how the polymer (1) flows during mold filling The flow depends on the (2) rheo-

logical properties o the polymer melt which in turn depends on the (3) heat trans-

fer inside the cavity The heat transer is dependent on the (4) thermal properties o

the polymer The deormation during flow causes (5) fiber orientation (6) fiber dam- age and possibly (7) material degradation The orientation and fiber length dis-

tribution resulting rom the fiber damage lead to (8) anisotropy in the finished

product that determines the (9) mechanical behavior o the part The anisotropic

mechanical behavior o the finished product depends on the combined (10) mechan-

ical properties o the basic materials that compose the original resin The final

mechanical properties control the (11) stresses and mechanical response o the

(12) assembly and its (13) functionality In turn the maximum torque within this

system is also controlled by the (14) friction coefficients o the materials At the end

o its service lie it may be necessary to (15) disassemble the gears i the (16)

choice of materials does not permit recycling o the assembled part Furthermore

at the end o product service lie the (17) regulations and legislations may have

changed perhaps banning the use o a specific material or additive Furthermore

the (18) material cost (19) mold cost (20) machine or molding costs (21) energy

consumption during processing and the (22) value of the recovered resin from sprue

and runner systems as well as from post-service life recycling are all o extreme

importance

12 General Information

Plastics have become the most important material in many fields and applications

They are lightweight some have excellent optical properties some are electric and

thermal insulators and in general they are easier and less expensive to make and

to process into a final product Some o their properties exceed the properties omore traditional materials while in other areas they are no match to conventional

engineering materials Figure 13 compares polymers to other materials with steel

providing the reerence (= 10) While the mechanical properties o steel aluminum

and ceramics all clearly outperorm those o thermoplastics thermoplastic mate-

rials are much lighter can be processed at significantly lower temperatures and

are excellent thermal insulators

Polymers are differentiated in three categories thermoplastics thermosets or

elastomers Thermoplastics in turn include a special amily called thermoplastic

elastomers However all these material have in common that they are made o

large molecules Some o these molecules are not crosslinked which means that

each molecule can move reely relative to its neighbors and others are crosslinked

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

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983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

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983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

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983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

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983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

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983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

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Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

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983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 25: CH-1Material Science of Polymers for Engineers

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983089983090 General Information 983095

which means that ldquobridgesrdquo or physical links interconnect the polymer molecules

Thermoplastics and un-vulcanized elastomers are non-crosslinked Vulcanized

rubbers or elastomers and thermosets are crosslinked

Thermoplastics are polymers that solidiy as they are cooled no longer allowing

the long molecules to move reely and when heated again these materials regain

the ability to ldquoflowrdquo as the molecules are able to slide past each other with ease

Thermoplastic polymers are divided into two classes amorphous and semi-crystal-

line polymers Amorphous thermoplastics are those with molecules that remain

in disorder as they cool leading to materials with a airly random molecular struc-

tures An amorphous polymer solidifies or vitrifies as it is cooled below its glass

transition temperature T g Semi-crystalline thermoplastics on the other hand

solidiy while establishing a certain order in their molecular structure Hence asthey are cooled they harden when the molecules begin to arrange in a regular

order below what is usually reerred to as the melting temperature T m The mole-

cules in semi-crystalline polymers that are not transormed into ordered regions

remain in small amorphous regions These amorphous regions within the semi-

crystalline domains lose their ldquoflowabilityrdquo below their glass transition tempera-

ture Most semi-crystalline polymers have a glass transition temperature at subzero

temperatures hence behaving like rubbery or leathery materials at room tempe-

rature On the other hand thermosetting polymers solidiy by a chemical curing

process Here the long macromolecules crosslink with each other during curing

resulting in a network o molecules that cannot slide past each other The orma-

tion o these networks causes the material to lose the ability to ldquoflowrdquo even afer

Figure 13 Properties o thermoplastics aluminum and ceramics with respect to steel

(Courtesy E Schmachtenberg)

Density

0001

Pricedm3

Pricekg

Strength

Stiffness

Thermal expansion

Thermal conductivity

Melting temperature

10010100001001

Properties with respect to steel (steel = 10)

Thermoplastics

Aluminum

Ceramics

Steel

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

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983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

7252019 CH-1Material Science of Polymers for Engineers

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983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3138

983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3238

983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3338

983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3538

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 26: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

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983096 1 Introduction

reheating A high crosslinking density between the molecules makes thermo-

setting materials stiff and brittle Thermosets also exhibit a glass transition tem-

perature that is sometimes near or above thermal degradation temperatures The

crosslinks between the molecules are chemical bonds such as covalent and ionic

bonds Another general type o bond between molecules in polymers is a physicalbond such as van der Waals forces Finally another type o bond is the hydrogen

bond that results rom the attraction between a hydrogen atom and an electro-

negative atom such as oxygen or nitrogen The highest bond strength results rom

a chemical bond and the lowest rom a physical bond [1]

Compared to thermosets elastomers are only lightly crosslinked which permits

almost ull extension o the molecules However the links across the molecules

hinder them rom sliding past each other making even large deormations rever-

sible One common characteristic o elastomeric materials is that the glass tran-sition temperature is much lower than room temperature Their ability to ldquoflowrdquo is

lost afer they are vulcanized or crosslinked Because at room temperature

crosslinked elastomers are significantly above their glass transition temperature

they are very sof and very compliant elastic solids

Table 11 presents the most common amorphous and semi-crystalline thermoplas-

tics as well as thermosets and elastomers with some o their applications Table

12 presents many polymers and their ISO abbreviations Today polymers are

ound everywhere The skier in Fig 14 presents just one example o where we can

find polymers in everyday lie He is protected by a helmet that is composed o

various polymer components His skiing equipment is also composed o a variety

o polymers and polymer composites and he is keeping warm using layers o

polymer abrics and insulating materials It should be pointed out that not all the

polymer components the skier is wearing are listed in the figure and that in

addition to the specific polymers listed in Fig 14 there are many more options o

polymeric materials to choose rom For example some skiing boots are reinorced

with aramid fibers

There are thousands o different grades o polymers available to the design engi-neer These materials cover a wide range o properties rom sof to hard ductile to

brittle and weak to tough Figure 15 shows this range by plotting important aver-

age properties or selected polymers The values corresponding to each material in

Fig 15 represent only an average There is a wide range in properties even or

materials o the same class The range in properties is ofen increased by the di-

erent additives and fillers that a resin may contain At this point it is important to

note that the properties listed in Fig 15 should not be used or design decisions

The properties represent a general trend in stiffness and toughness o the various

materials and should be used only when comparing one material against another

As will be discussed in later chapters properties that are used in design need to be

time-dependent such that loading time or loading rate can be included as design

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2738

983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2838

983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2938

7252019 CH-1Material Science of Polymers for Engineers

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3138

983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3238

983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3338

983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3538

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 27: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2738

983089983090 General Information 983097

Table 11 Common Polymers and Some o Their Applications

Polymer Applications

Thermoplastics

Amorphous

Polystyrene Mass-produced transparent articles thermoormed packaging

oamed packaging and thermal insulation products etc

Polymethyl methacrylate Skylights airplane windows lenses bulletproo windows

automotive stop lights etc

Polycarbonate Helmets eyeglass lenses CDrsquos hockey masks bulletproo

windows blinker lights head lights etc

Unplasticized polyvinyl chloride Tubes window rames siding rain gutters bottles thermoormed

packaging etc

Plasticized polyvinyl chloride Shoes hoses roto-molded hollow articles such as balls and other

toys calendered films or raincoats and tablecloths etcSemi-crystalline

High density polyethylene Milk and soap bottles mass production o household goods o

higher quality tubes paper coating etc

Low density polyethylene Mass production o household goods squeeze bottles grocery

bags etc

Polypropylene Goods such as suitcases tubes engineering application

(fiberglass-reinorced) housings or electric appliances etc

Polytetrafluoroethylene Coating o cooking pans lubricant-ree bearings etc

Polyamide Bearings gears bolts skate wheels pipes fishing line textiles

ropes etc

Thermosets

Epoxy Adhesive glass fiber reinorced automotive lea springs carbon

fiber reinorced bicycle rames aircraf wings and uselage etc

Melamine Decorative heat-resistant suraces or kitchens and urniture

dishes etc

Phenolics Heat-resistant handles or pans irons and toasters electric

outlets etc

Unsaturated polyester Toaster sides iron handles satellite dishes glass fiber reinorced

breaker switch housings and automotive body panels etc

Elastomers

Polybutadiene Automotive tires (blended with natural rubber and styrene

butadiene rubber) gol ball skin etc

Ethylene propylene rubber Automotive radiator hoses and window seals roo covering etc

Natural rubber (polyisoprene) Automotive tires engine mounts etc

Polyurethane elastomer Roller skate wheels sport arena floors ski boots automotive

seats (oamed) shoe soles (oamed) etc

Silicone rubber Seals parts or medical applications membranes heat resistant

kitchen containers etc

Styrene butadiene rubber Automotive tire treads etc

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2838

983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2938

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3038

983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3138

983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3238

983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3338

983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3538

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 28: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2838

983089983088 1 Introduction

Table 12 Abbreviations o Common Polymers (TP = thermoplastic E = elastomer

TS = thermoset)

Polymer Abbrev (Type) Polymer Abbrev (Type)

Acrylonitrile-butadiene-styrene ABS (TP) Polyether ether ketone PEEK (TP)

Butadiene rubber BR (E) Polyether sulone PES (TP)

Cellulose acetate CA (TP) Polyethylene

terephthalate

PET (TP)

Cellulose acetate butyrate CAB (TP) Polyimide PI (TP)

Cellulose nitrate CN (TP) Polyisobutylene PIB (TP)

Epoxy EP (TS) Polymethyl

methacrylate

PMMA (TP)

Ethylene-propylene-diene rubber EPDM (E) Polyphenylene sulfide PPS (TP)

Expanded polystyrene EPS (TP) Polyphenylene sulone PPSU (TP)

High density polyethylene PE-HD (TP) Polypropylene PP (TP)

Impact resistant polystyrene PS-HI (TP) Polypropylene

copolymer

PP-CO (TP)

Linear low density polyethylene PE-LLD (TP) Polystyrene PS (TP)

Linear medium density polyethylene PE-LMD (TP)

Liquid crystalline polymer LCP (TP) Polysulone PSU (TP)

Low density polyethylene PE-LD (TP) Polytetrafluoroethylene PTFE (TP)

Melamine-ormaldehyde MF (TS) Polyurethane PUR (TS)

Metallocene catalyzed polyethylene mPE (TP) Polyvinylidene acetate PVAC (TP)

Natural rubber NR (E) Polyvinyl alcohol PVAL (TP)

Olefinic thermoplastic elastomer TPO (TP) Polyvinyl carbazole PVK (TP)

Phenol-ormaldehyde (phenolic) PF (TS) Polyvinyl chloride PVC (TP)

PF mineral filled moldings PF-m (TS) Polyvinylidene fluoride PVDF (TP)

PF organic filled moldings PF-o (TS) Rigid PVC PVC-U (TP)

Plasticized PVC PVC-P (TP) Silicone SI (E)

Polyacetal (polyoxymethylene) POM (TP) Silicone rubber SI (E)

Polyacrylate PAR (TP) Styrene-acrylonitrile

copolymer

SAN (TP)

Polyacrylonitrile PAN (TP) Thermoplastic

elastomer

TPE (TP)

Polyamide 6 PA6 (TP) Thermoplastic poly-

urethane elastomer

TPU (TP)

Polyamide 66 PA66 (TP) Unsaturated polyester UP (TS)

Polybutylene terephthalate PBT (TP) Urea-ormaldehyde UF (TS)

Polycarbonate PC (TP) Vinyl ester resin VE (TP)

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2938

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3038

983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3138

983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3238

983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3338

983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

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7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 29: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 2938

7252019 CH-1Material Science of Polymers for Engineers

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983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3138

983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3238

983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3338

983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3538

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 30: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3038

983089983090 1 Introduction

100

10

1000 20

15

10

10

10

100

1000

Elongationat break

at 23degC ASTM D 638

IZOD impactstrength

Jm (notched 23degC) ASTM D 256

Specific gravity ASTM D 792

HIPS HIPS

HIPS

PP

PP

PP

PC PC

PC

PVC

PVC

PVC

Epoxy

Epoxy

EpoxyPhenolic

Phenolic

Phenolic

POM

POM

POM

PMMA

PMMA

PMMA

PET

PET

PET

PA66

PA66PA66

HDPE

HDPE

HDPE

LDPE

LDPE no break

LDPE

05

PSPS

PS

SANSAN

SAN

ABS

ABS

ABS

PTFE

PTFE

PTFE

PI

PI

PI

UP

UP

UP

20

Market price $ lb(March 2010)

300

200

100

00

5

10

15200

150

100

50

0

1000

10000

100

Deflectiontemperature degCunder flexuralload (182 MPa) ASTM D 648

Thermalexpansioncoefficient

10-5 mm degC ASTM D 696

Tensilestrength MPaat 23degC ASTM D 638

Flexuralmodulus MPaat 23degC ASTM D 790

HIPS

HIPS

HIPS

HIPSPP

PP

PP

PP

PC PC

PC

PC PVC

PVC

PVC

PVC

Epoxy

Epoxy

Epoxy

EpoxyPhenolic

PhenolicPhenolic

Phenolic

POM

POM

POM

POM

PMMA

PMMA

PMMA

PMMA

PET

PET

PET

PET

PA66

PA66

PA66

PA66

HDPE

HDPE

HDPE

HDPELDPE

LDPE

LDPE

LDPEPS

PS

PS

PS

SAN

SAN

SAN

SAN

ABS

ABS

ABS

ABS

PTFE

PTFE

PTFE

PTFE

PI

PI

PI

PI

UP

UP

UP

UP

20

10

15

10

07PETHDPE Phenolic

LDPEPS

PMMA

HIPS

PI

EpoxyPP

SAN

UP

PVC

PC

ABSPOM

PTFE

PA66

ABS HDPEPET Recycled

grades

Figure 15 Average properties or common polymers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3138

983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3238

983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3338

983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3538

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 31: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3138

983089983091 Identification of Polymers 983089983091

13 Identification of Polymers

Perhaps one o the most important skills a plastics design engineer needs to haveis the ability to identiy a specific polymer or polymer component An experienced

plastics engineer can ofen identiy a polymer by touching smelling or tapping it

However the complete identification o the chemical composition additives and

fillers o a plastic material is an extremely complicated task To achieve this equip-

ment that perorms differential scanning calorimetry inrared spectroscopy and

dynamic mechanical analysis to name a ew is available3 Most process and design

engineers do not have these measuring devices at hand nor do they have the ana-

lytical experience to run them and interpret the resulting data However ofen only

simple means are needed in addition to basic knowledge o polymer chemistry to

identiy a polymer Through simple observation a burn test and experience an

engineer is able to identiy most plastics Figure 16 presents a summarized guide

to aid in the identification o polymers

Inormation presented in guides such as in Fig 16 are only helpul when used

with common sense and engineering insight For example the attribute labeled

ldquoAppearancerdquo can sometimes be misleading Depending on the additives or color-

ants added even an amorphous thermoplastic such as polystyrene can be opaque

The stiffness attribute is broken down into three categories flexible semi-rigidand rigid Flexible are those materials that eel rubbery or leathery while mate-

rials are semi-rigid when they are strong and stiff but can deflect a substantial

amount The materials that all under the rigid category are those that are stiff but

brittle During the burn test make sure not to inhale the umes released by a burn-

ing plastic or those released soon afer extinguishing the burning polymer Even

without directly inhaling the umes one can still discern the particular smells o

the material during the burning test Due to the benzene ring in their molecular

structure styrenic materials such as PS ABS and SAN have a sweet smell while

polyolefin plastics such as PE and PP smell waxy Because o the nitrogen atoms in

their structure polyamides can smell like burning hair When burning POM a

strong smell o ormaldehyde is released Burning PVC releases HCl To no sur-

prise cellulose plastics smell like burning paper All burn tests must be perormed

under a ventilation hood or in a well ventilated room

3 These tests are discussed in detail in Chapters 3 and 8 o this book

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3238

983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3338

983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3538

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 32: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3238

983089983092 1 Introduction

Appearance SurfaceStiffness Burn test

T r a n s p a r e n t

T r a n s p a r e n t ( t h i n f i l m )

T r a n s l u s c e n t

O p a q u e

F l e x i b l e ( r e s i l i e n t )

S e m i - r i g i d

R i g i d ( B r i t t l e )

G l a s s y

W a x y

D u l l

B l a c k s o o t

B u r n s c l e a n

S e l f e x t i n g u i s h i n g

D r i p s

D o e s n o t d r i p

Y e l l o w f l a m e

B l u e f l a m e

G r e e n f l a m e

PE-LD

PE-HD

PP

PP-CO

PS

PS-HI

SAN

ABS

PVC-R

PVC-P

PTFE

PVDF

PVAC

PVAL

PMMAPOM

PA6

PA66

PSU

PI

CA

CAB

CN

PCPET

PBT

PF

PF-MF

PF-OF

UP

EP

PUR

SI

Figure 16 Plastics identification attributes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3338

983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3538

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 33: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3338

983089983092 Sustainability ndash The 983094th P 983089983093

14 Sustainability ndash The 6th P

The first edition o this book was published at the end o the 20th century when theterm bdquosustainabilityldquo was used by only a ew and recycling o plastics was starting

to become a topic o environmental and economic interest Today 15 years afer the

publication o that first edition and already in the second decade o the 21st

century we live in a world that is orced to think and act with the environment in

mind While topics such as biopolymers biodegradability and biocompatibility are

playing an increasingly more important role in this arena recycling is the main

topic that we consider within the 6th P Post-consumer lie

We can divide plastics recycling into two major categories industrial and postcon-sumer plastic scrap recycling Industrial scrap is easily recycled and re-introduced

into the manuacturing stream either within the same company as a regrind or

sold to third parties as a homogeneous reliable and uncontaminated source o

resin Post-consumer plastic scrap recycling requires the material to go through a

ull lie cycle prior to being reclaimed This lie cycle can last rom a ew days or

packaging material to several years or electronic equipment housing material

Post-consumer plastic scrap can origin rom commercial agricultural or muni-

cipal waste Municipal plastic scrap primarily consists o packaging waste but also

plastics rom de-manuactured retired appliances and electronic equipment

Post-consumer plastic scrap recycling requires collecting handling cleaning sort-

ing and grinding Availability and collection o post-consumer plastic scrap is per-

haps one o the most critical aspects Today the demand or recycled plastics is

higher than the availability o these materials Although the availability o HDPE

rom bottles has seen a slight increase the availability o recycled PET bottles has

decreased in the last ew years One o the main reasons or the decrease o post-

consumer PET is the act that single-serving PET bottles are primarily consumed

outside o the home making recycling and collection more difficult On the other

hand HDPE bottles which come rom milk containers soap and cleaner bottles

are consumed in the home and are thereore thrown into the recycling bin by the

consumer A crucial issue when collecting plastic waste is identiying the type o

plastic used to manuacture the product Packaging is ofen identified with the

standard SPI identification symbol which contains the triangular-shaped recyc-

ling arrows and a number between 1 and 7 Ofen this is accompanied by the

abbre viated name o the plastic Table 13 and Fig 17 present the seven commonly

recycled plastic materials in the United States along with the characteristics o

each plastic the main sources or packaging applications and the common appli-cations or the recycled materials Electronic housings are ofen identified with a

molded-in name o the polymer used such as ABS as well as an identifier that

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3538

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 34: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3438

983089983094 1 Introduction

Table 13 Plastics Characteristics Applications and Use Afer Recycling

Codes Characteristics Packaging Applications Recycled Products

(1) PET Clarity strength

toughness barrier to

gas and moisture

resistance to heat

Plastic bottles or sof drink

water sports drink beer

mouthwash catsup and salad

dressing peanut butter

pickle jelly and jam jars

heatable film and ood trays

Fiber tote bags clothing film

and sheet ood and beverage

containers carpet strapping

fleece wear luggage and

bottles

(2) PE-HD Stiffness strength

toughness resistance

to chemicals and

moisture permeability

to gas ease o pro-

cessing and ease o

orming

Milk water juice shampoo

dish and laundry detergent

bottles yogurt and margarine

tubs cereal box liners

grocery trash and retail bags

Liquid laundry detergent

shampoo conditioner and

motor oil bottles pipe

buckets crates flower pots

garden edging film and sheet

recycling bins benches dog

houses plastic lumber floor

tiles picnic tables encing

(3) PVC Versatility clarity

ease o blendingstrength toughness

resistance to grease

oil and chemicals

Clear ood and non-ood

packaging medical tubingwire and cable insulation film

and sheet construction pro-

ducts such as pipes fittings

siding floor tiles carpet

backing and window rames

Packaging loose-lea binders

decking paneling guttersmud flaps film and sheet

floor tiles and mats resilient

flooring electrical boxes

cables traffic cones garden

hose mobile home skirting

(4) PE-LD Ease o processing

strength toughness

flexibility ease o

sealing barrier to

moisture

Dry cleaning bread and

rozen ood bags squeezable

bottles e g honey mustard

Shipping envelopes garbage

can liners floor tile urniture

film and sheet compost bins

paneling trash cans land-

scape timber lumber

(5) PP Strength toughnessresistance to heat

chemicals grease and

oil versatile barrier to

moisture

Catsup bottles yogurtcontainers and margarine

tubs medicine bottles

Automobile battery casessignal lights battery cables

brooms brushes ice scrapers

oil unnels bicycle racks

rakes bins pallets sheeting

trays

(6) PS Versatility insulation

clarity easily ormed

Compact disc jackets ood

service applications grocery

store meat trays egg cartons

aspirin bottles cups plates

cutlery

Thermometers light switch

plates thermal insulation egg

cartons vents desk trays

rulers license plate rames

oam packing oam plates

cups utensils

(7) Other Dependent on resin or

combination o resins

Three and five gallon reusable

water bottles some citrus

juice and catsup bottles

Bottles plastic lumber

applications

1 2 3 4 5 6 7

PETE HDPE V LDPE PP PS OTHER

Figure 17 SPI resin identification codes

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3538

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 35: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3538

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 36: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3638

983089983096 1 Introduction

Table 14 Plastic Bottle Recycling Statistics or 2010 (American Plastics Council)

Plastic bottle type Resin sold (mill Lb) Recycled plastic Recycling rate

PET 5350 1557 291

PE-HD natural 1604 4341 271

PE-HD pigmented 1682 5500 327

Total PE-HD bottles 3286 9841 299

PVC 68 14 20

PE-LD 56 10 19

PP 193 354 183

Total 8953 2579 288

-100

-80

-60

-40

-20

0

POM (MFI0 = 1548)

PC (MFI0 = 210)

PP (MFI0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 029)

Extrusion

Processing event number

( ( M F I 0 -

M F I

F ) M F I 0 ) x 1 0 0

0 1 2 3 4 5

20

40

Figure 18 Change in MFI as a unction o number o extrusion processing events

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 37: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3738

Problems

1 Determine what material was used to abricate the samples supplied to

you by the instructor

2 An opaque semi-rigid plastic toy with a smooth surace is subjected to a

burn test It does not drip as it burns clean with a blue flame There is a

penetrating smell when the flame is extinguished What material was

used to manuacture this toy Which o the above attributes shouldusually not be taken into account in the decision process

3 A transparent and stiff cup that is involved in a Hamburger-Burger ldquocold

juice spillrdquo lawsuit is given to you by a group o lawyers O the various

materials it could be made o what is your first guess Explain

4 A competitor o yours makes a toy that is opaque stiff and has a smooth

surace You want to know what material it is made o You burn a corner

o the toy The flame is yellow What do you conclude rom your tables

Which one o the attributes can you eliminate to make your decision

easier5 What general type o plastic are you dealing with that does not melt

when heated and remains relatively rigid

-100

-80

-

60

-40

-20

0

20

40

( ( M F I 0 -

M F I F ) M F I 0 ) x 1 0 0

Processing event number

PC (MFI0 = 210)

PP (MFI 0 = 305)

PLA (MFI0 = 1420)

PMMA (MFI0 = 2110)

LDPE (MFI0 = 197)

HDPE (MFI0 = 3780)

Injection

0 1 2 3 4 5

Figure 19 Change in MFI as a unction o number o injection molding processing events

983089983092 Sustainability ndash The 983094th P 983089983097

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)

Page 38: CH-1Material Science of Polymers for Engineers

7252019 CH-1Material Science of Polymers for Engineers

httpslidepdfcomreaderfullch-1material-science-of-polymers-for-engineers 3838

983090983088 1 Introduction

6 Write the combustion reaction when burning a PVC sample

7 What material would you select to manuacture saety helmets to be

used in a chemical plant

References

[1] Calhoun A and Peacock A Polymer Chemistry ndash Properties and Applications

Hanser Publishers Munich (2006)

[2] Termonia Y and Smith P High Modulus Polymers A E Zachariades and R S Por-

ter Eds Marcel Dekker Inc New York (1988)[3] Ehrenstein G W Faserverbund-Kunststoffe Hanser Publishers Munich (2006)

[4] Naranjo A Noriega M Osswald T A Roldaacuten A and Sierra J Plastics Testing and

Characterization ndash Industrial Applications Hanser Verlag Muumlnchen (2006)

[5] Saacutenchez K Stoumlckl K Perdomo A and Osswald T A Journal of Plastics Tech-

nology accepted or publication (2012)