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7/30/2019 Patrics Hand-out 3

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Polymer Blends

- Homogeneous blends

- miscible on molecular scale,

mobility is averaged, consequently glass transition

temperatures are averaged

- Heterogeneous blends

p. 295

- not miscible but phase separated,

mobility of original phases present, consequently glass

transition temperatures of original phases are present

Miscibility and modulus

M

Purecomponents

Tg1 Tg2

Tg12

M

Miscibleblend

Tg1 Tg2

M

T

Immiscibleblend


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Phase Behaviour of Blends

Change of Gibbs free energy Gm should be negative and second derivativewith respect to volume fraction must be larger than zero for complete

Gm = Hm - TSm

.

- Complete miscibility seldom in highmolecular systems because of entropyeffects (Sm 0) favourable interactionsare necessary (0 > Hm)

p. 297

- Heterogeneous blends common

Phase Behaviour of Blends

Example: Polystyrene Polycarbonate blends shows LCST behaviour

Decreasing molecular

Lower Critical

Solution Temperature

weight of PS

p. 299


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Commercial Miscible Polymer Blends

p. 303

Glass Transition and Crystallisation in PVDF/PMMA

Poly(vinylidene fluoride) can crystallisedepending on composition andtemperature. PMMA serves like a diluent

and lowers the meltin tem erature.

p. 303


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Properties of Blends

p. 304

Toughened Plastics and Phase Separated Blends

Example: high-impact Polystyrene (HIPS)

Promotion ofextensive shearyielding or crazeformation

p. 306


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Interpenetrating Networks

Example: IPN of poly(ethyl acrylate) and polystyrene

p. 307

Properties of Fibers

p. 290


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Properties of Matrices

p. 309

Mechanical Properties

Modulus : in the fiber direction in uniaxial reinforced composite

EL = (1-f) Em + f Ef

Strength :

L = (1-f) m + f f

p. 310

Reinforcement in perpendicular direction much lower and dependent oninterfacial adhesion between fiber and matrix.


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Interfacial Adhesion and Coupling Agents

p. 312

Nanocomposites

p. 316


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Nanocomposites properties

p. 315

Nanocomposite Structure

Exfoliated nanoclay in a polymer matrix


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Polysulfone Nanocomposites

p. 317

Composite Processing: Filament Winding

Products: pipes,tanks, flagpoles

p. 318


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Composite Processing: Pultrusion

Continuous moulding process for profiles utilizing glassor other fibrous reinforcement in a polyester or otherresin matrix

p. 319

Polymer Processing and Rheology

Basic steps for processing thermoplastics and elastomers:

heating of material

Rheology is science of flow of materials

p. 427

transport of hot melt

shape realization

fixation of shape


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Extrusion Process

- Extrusion is a continuous process to produce:tubes, profiles, cables, plates, foils, fibers, bottles

tratt

silpaket

skruv

vrmeelement termoelement gngamatar-ficka

p. 429

matarzonkompressionszonskjuvzon

munstycke

mantel

Extrusion Process


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Molding Processes

Moldin : discontinuous rocess

- injection molding

- reaction injection molding

- compression molding

- transfer molding

- thermoforming termoformning, vacuumformning

formpressning

reaktiv formsprutning

formsprutning

sprutpressning

p. 429

- blow molding

- rotational molding

formblsning

rotationsgjutning

Injection Molding

un yc e

p. 432


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Injection Molding

Injection Molding

p. 433

inlopp frdelningskanal

formrumskanal

formrum

frgreningskanal

kallplugg


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Reaction Injection Molding

RIM process with two separate tanks for polymerisation reagents

Polyamides

Epoxies

Polyurethanes

p. 434

Compression Molding Process

A. View of open mold withmolding material in place

B. Closed mold showing formed partand flash formed from excess resin

p. 430


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Transfer Molding

A. Transfer potis loaded whilemold is in closed position

.into mold form

C. Mold opens and ejector pins pushout molded part

p. 431

Thermoforming

Also called vacuumforming

p. 435

A. Flat sheet is heated

B. Softened sheet is forcedto fit the mold contour byevacuating the spacebetween the sheet and themold


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Blow Molding

Extrusion blow-molding process in the production of plastic bottles

p. 436

PET preforms forinjection blow molding

Calendering

Production of plastic sheet of PVC, PVC blends and copolymers of PVC

Simplified representation ofa calendering process,usually several cylindersinvolved

p. 437


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Coating

A. Roll coating

B. Blade coating

p. 437

C. Curtain coating

Polymer Rheology

Shear stress is proportional to shear rate

The viscosit is

p. 440


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Viscosity of Polymer Melts

Typical behaviour of a polymeric melt

Zero-shear viscosity

-avarage molecular mass

p. 442

Rheometry

Measurement techniques:

Capillary rheometer

Couette rheometer

p. 461

Cone-and Plate rheometer


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Capillary Rheometer

Range : shear rates from 1 105 s-1

By measuring pressure drop over thecapillary and volumetric flow rate theshear stress and shear strain rate can becalculated and thus the viscosity.

p. 462

Couette Rheometer

The shear stress is determinedby measuring the torque, theshear rate is determined by theangular velocity and dimensions ofthe system.

p. 465


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Cone-and Plate Rheometer

Why using a cone ? Cone angle is very small, 1-3 degrees

Shear rate is independent on R !

p. 467

ear ra e

Shear stress is proportional to torque

Viscosity measurements

Polymer melts at 200 oC

HDPE

PP

PSPMMA

LDPE

p. 468

Cone-and-plate

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