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Plastics Design Library Introduction

Introduction

Polypropylene is a versatile thermoplastic mate-

rial, compatible with many processing techniques

and used in many different commercial applica-

tions. [797] It is one of the fastest growing classesof commodity thermoplastics, with a market share

growth of 67%/year, and the volume of polypro-

pylene produced is exceeded only by polyethylene

and polyvinyl chloride. [794, 790]

The moderate cost and favorable properties of

polypropylene contribute to its strong growth rate. It

is one of the lightest of all thermoplastics (0.9 g/cc),

so that fewer pounds are required for finished parts.

Due to its high strength-to-weight ratio, it is more

rigid than other polyolefins. It has the highest

melting temperature (160170C; 320338F) of allcommodity thermoplastics and better heat resistance

than other low-cost thermoplastics; unmodified

polypropylene, however, becomes brittle at subam-

bient temperatures. [696, 794]

Its excellent chemical resistance includes re-

sistance to most organic solvents, except for very

strong oxidizing agents; however, softening may

occur due to the permeation of chlorinated sol-

vents and hydrocarbons. Its good fatigue resistance

makes it widely used in living hinge applications in testing, oriented thin sections can withstand

more than one million repeated flexings. It is usu-

ally not susceptible to environmental stress crack-

ing. Its clarity is greater than that of other polyole-

fins, and many grades can withstand commonly

used sterilization methods. [696, 699]

Polypropylene is available in a wide variety of

melt flow rates, ranging from 0.3 to over 1000 g/10

min., and it is easily recycled. It can be processed

by virtually all methods, including injection mold-

ing, blow molding, extrusion, blown and cast film,and thermoforming. [795, 794, 797, 796, 693]

Many available grades with different properties

make polypropylene useful in applications such as

fibers, films, filaments, and injection molded parts

for automobiles, rigid packaging, appliances, medi-

cal equipment, food packaging, and consumer

products. It is being substituted for glass, metal, and

engineering plastics such as ABS, polycarbonate,

polystyrene, and nylon in kitchen appliances and

large appliances such as ovens, dishwashers, refrig-erators, and washing machines, and high flow

grades are used in molding large housewares. Su-

per-soft grades are replacing polyvinyl chloride in

medical bags and tubing and in hospital gowns.

[797, 791, 793, 792, 696, 776]

Polypropylene The Definitive Users Guideprovides detailed information on the science and

technology of polypropylene. The book includes

chapters on the chemistry and morphology of poly-

propylene, common additives and fillers, and design

and processing. Detailed discussions of injection

molding, extrusion, blow molding, thermoforming,

and fabricating polypropylene are presented in sepa-

rate chapters. Descriptions of common product

forms foams, fibers, films, and sheets are

provided, in addition to commercially available

forms of resins: homopolymer and random and im-pact copolymers. In other chapters, the many appli-

cations of polypropylene, recycling methods, and

the safety and health aspects of polypropylene in

use and processing are described. Properties and

characteristics of polypropylene and the effect of

chemistry, morphology, and processing on these

characteristics are discussed.

Other sections contain extensive lists of data

sheet properties for representative, commonly used

grades of polypropylene and an extensive compi-lation of data in tabular and graphical form that in-

cludes creep data, stress-strain data, fatigue, effect

of UV light and weathering, effect of sterilization

methods, film properties, temperature-mechanical

property relationships, composition-mechanical

property relationships, temperature-thermal prop-

erty relationships, stress relaxation data, viscosity

data, data on thermodynamic properties, and

chemical and environmental stress crack resis-

tance. Each table or graph is designed to stand

alone, be easy to interpret, and provide all relevantand available details of test conditions and results.

This publication serves to turn the vast amount

of disparate information from wide ranging

sources (i.e., conference proceedings, materials

suppliers, test laboratories, monographs, and trade

and technical journals) into useful engineering

knowledge. Although substantial effort is exerted

throughout the editorial process to maintain accu-

racy and consistency in presentation of informa-

tion, the possibility for error exists. Often these er-rors occur due to insufficient or inaccurate in-

formation in the source document.

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Plastics Design Library

How a material performs in its end use envi-

ronment is a critical consideration and the infor-

mation here gives useful guidelines. However, this

or any other information resource should not serve

as a substitute for actual testing in determining the

applicability of a particular part or material in a

given end use environment.Although the book contains information and

data from many sources, the information is ar-

ranged to be easily accessible to readers; flexibil-

ity and ease of use were carefully considered in

designing the layout of this book. It is organized

so that information of interest, whether general in-

formation or detailed test data, can be quickly

found, using the general index, the index of fig-

ures, the index of tables, the detailed table of con-

tents, or the numerous sub-headings within eachchapter. For readers who wish to delve beyond the

data presented, detailed source documentation is

provided in the reference index; for those for

whom polypropylene is a relatively new field, the

glossary of terms will prove useful.

We trust you will greet this reference publica-

tion with the same enthusiasm as previous Plastics

Design Library titles and that it will be a useful toolin your work. As always, your feedback on im-

proving this volume or others in the PDL Handbook

series is appreciated and encouraged.

Plastics Design Library

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E-mail: publishing@williamandrew.com

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