1

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

MMiscibleblend

Tg1 Tg2

M

T

Immiscibleblend

2

Phase Behaviour of Blends

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

Gm = Hm - TSm

miscibility.

- Complete miscibility seldom in high molecular systems because of entropy effects (Sm≈ 0) favourable interactions are 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

g

weight of PS

p. 299

3

Commercial Miscible Polymer Blends

p. 303

Glass Transition and Crystallisation in PVDF/PMMA

Poly(vinylidene fluoride) can crystallise depending on composition and temperature. PMMA serves like a diluent and lowers the melting temperature.

p. 303

and lowers the melting temperature.

4

Properties of Blends

p. 304

Toughened Plastics and Phase Separated Blends

Example: high-impact Polystyrene (HIPS)

Promotion of extensive shear yielding or craze formation

p. 306

5

Interpenetrating Networks

Example: IPN of poly(ethyl acrylate) and polystyrene

p. 307

Properties of Fibers

p. 290

6

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

f m f f

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

7

Interfacial Adhesion and Coupling Agents

p. 312

Nanocomposites

p. 316

8

Nanocomposites properties

p. 315

Nanocomposite Structure

Exfoliated nanoclay in a polymer matrix

9

Polysulfone Nanocomposites

p. 317

Composite Processing: Filament Winding

Products: pipes, tanks, flagpoles

p. 318

10

Composite Processing: Pultrusion

Continuous moulding process for profiles utilizing glass or other fibrous reinforcement in a polyester or other resin 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

11

Extrusion Process

- Extrusion is a continuous process to produce:

tubes, profiles, cables, plates, foils, fibers, bottles

tratt

silpaket

skruv

värmeelement termoelement gängamatar-ficka

p. 429

matarzonkompressionszonskjuvzon

munstycke

mantel

Extrusion Process

12

Molding Processes

Molding: discontinuous processMold ng d scont nuous process- injection molding

- reaction injection molding

- compression molding

- transfer molding

- thermoforming termoformning, vacuumformning

formpressning

reaktiv formsprutning

formsprutning

sprutpressning

p. 429

- blow molding

- rotational molding

formblåsning

rotationsgjutning

Injection Molding

m st k värmeelementmunstycke värmeelement

p. 432

13

Injection Molding

Injection Molding

p. 433

inlopp fördelningskanal

formrumskanal

formrum

förgreningskanal

kallplugg

14

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 with molding material in place

B. Closed mold showing formed part and flash formed from excess resin

p. 430

15

Transfer Molding

A. Transfer potis loaded while mold is in closed position

B Plunger pushes molding material B. Plunger pushes molding material into mold form

C. Mold opens and ejector pins push out molded part

p. 431

Thermoforming

Also called vacuum forming

p. 435

A. Flat sheet is heated

B. Softened sheet is forced to fit the mold contour by evacuating the space between the sheet and the mold

16

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 of a calendering process, usually several cylinders involved

p. 437

17

Coating

A. Roll coating

B. Blade coating

p. 437

C. Curtain coating

Polymer Rheology

Newton’s law of viscosity:Newton s law of viscosity:

Shear stress is proportional to shear rate

The viscosity is

p. 440

The viscosity is

18

Viscosity of Polymer Melts

Typical behaviour of a polymeric melt

Zero-shear viscosityis directly related to the weightis directly related to the weight-avarage molecular mass

p. 442

Rheometry

Measurement techniques:

Capillary rheometer

Couette rheometer

p. 461

Cone-and Plate rheometer

19

Capillary Rheometer

Range : shear rates from 1 – 105 s-1

By measuring pressure drop over the capillary and volumetric flow rate the shear stress and shear strain rate can be calculated and thus the viscosity.

p. 462

Couette Rheometer

The shear stress is determined by measuring the torque, the shear rate is determined by the angular velocity and dimensions of the system.

p. 465

20

Cone-and Plate Rheometer

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

Shear rate is independent on R !

Shear rate

p. 467

Shear rate

Shear stress is proportional to torque

Viscosity measurements

Polymer melts at 200 oC

HDPE

PP

PS PMMA

LDPE

p. 468

Cone-and-plate