1

Polymer Blends

p. 295

- homogeneous blends

-miscible on molecular scale,

mobility is avaraged, consequently glass transition

temperatures are avaraged

-inhomogeneous blends

not miscible but phase separated,

mobility of original phases present, consequently glass

transition temperatures of original phases are present

Phase Behaviour of Blends

p. 297

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.

- complete miscibility seldom in high molecular systems because of entropy effects, interactions are necessary

- inhomogeneous blends common

2

Phase Behaviour of Blends

p. 299

Example: Polystyrene – Polycarbonate blends shows LCST behaviour

Lower Critical Solution Temperature

Decreasing molecular mass of PS

Commercial Miscible Polymer Blends

p. 303

3

Glass Transition and Crystallisation in PVDF/PMMA

p. 303

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

Properties of Blends

p. 304

4

Toughened Plastics and Phase Separated Blends

p. 306

Example: high-impact Polystyrene (HIPS)

Promotion of extensive shear yielding or craze formation

Interpenetrating Networks

p. 307

Example: IPN of poly(ethyl acrylate) and polystyrene

5

Properties of Fibers

p. 290

Properties of Matrices

p. 309

6

Mechanical Properties

p. 310

Μodulus : in the fiber direction in uniaxial reinforced composite

EL = (1-φf) Em + φf Ef

Strength :

σL = (1-φf) σm + φf σf

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

Interfacial Adhesion and Coupling Agents

p. 312

7

Nanocomposites

p. 316

Nanocomposites properties

p. 315

8

Polysulfone Nanocomposites

p. 317

Composite Processing: Filament Winding

p. 318

- Pipes

- Tanks

- Flagpoles

9

Composite Processing: Pultrusion

p. 319

Continuous process for profiles

Polymer Processing and Rheology

p. 427

Basic steps for processing thermoplastics and elastomers:

• heating of material

• transport of hot melt

• shape realization

• fixation of shape

Rheology is science of flow of materials

10

Extrusion Process

p. 429

- Extrusion is a continuous process to produce:

tubes, profiles, cables, plates, foils, fibers, botles

Molding Process

p. 429

Molding: discontinuous process

- injection moulding

- reaction injection moulding

- compression molding

- transfer molding

- thermoforming

- blow molding

- rotational molding

11

Injection Molding

p. 432

Injection Molding

p. 433

12

Reaction Injection Molding

p. 434

RIM process with two separate tanks for polymerization reagents

Polyamides

Epoxies

polyurethanes

Compression Molding Process

p. 430

A. View of open mold with molding material in place

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

13

Transfer Molding

p. 431

A. Transfer potis loaded while mold is in closed position

B. Plunger pushes molding material into mold form

C. Mold opens and ejector pins push out molded part

Thermoforming

p. 435

Vacuum forming

A. Flat sheat is heated

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

14

Blow Molding

p. 436

Extrusion blow-molding process in the production of plastic bottles

Calendering

p. 437

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

Simplified representation of a calendering process, usually several cylinders involved

15

Coating

p. 437

A. Roll coating

B. Blade coating

C. Curtain coating

Polymer Rheology

p. 440

Newton’s law of viscosity:

Shear stress τ is proportional to shear rate γ

The viscosity is η = τ / γ

16

Viscosity of Polymer Melts

p. 442

Typical behaviour of a polymeric melt

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

Rheometry

p. 461

Measurement techniques:

Capillary rheometer

Couette rheometer

Cone-and Plate rheometer

17

Capillary Rheometer

p. 462

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.

Couette Rheometer

p. 465

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

18

Cone-and Plate Rheometer

p. 467

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

Shear rate is independent on R !

Shear rate = Ω / β

Shear stress is proportional to torque

Viscosity measurements

p. 468

Polymer melts at 200 oC

HDPE

PP

PS PMMA

LDPE

Cone-and-plate

19

Membrane Science and Technology

p. 486

• Barrier polymers

• Membrane separations: general

• Gas separation

• Mechanisms of transport

• Measurement of gas diffusion

• Membrane preparation

Barrier Polymers

p. 486

Applications: packaging films, botles, encapsulation of electronic parts

Permeability coefficient P < 10-11 cm3-cm/cm2-sec cmHg

at 0% humidity and 25 0C

Examples: PAN, PMAN

poly(ethylene terephthalate) : CO2

20

Permeability Coefficients of Polymers

p. 487

Calculation of Gas Permeabilities

p. 488

Group contribution scheme for calculating gas permeabilities

Permachor:

P(298) = P*(298) exp(-sπ)

21

Membrane Separations

p. 489

Applications for Microfiltration and Ultrafiltration

p. 490

22

Gas Separations

p. 492

Thomas Graham has in 1866 reported that the oxygen content of air could be enriched from 21% to 41% by permeation through a membrane of natural rubber

Gas Separations

p. 492

Examples:

• oxygen enrichment of air

• hydrogen separation from carbon monoxide and other gases

• removal of carbon dioxide from natural gas

• reduction of organic vapor concentration in air

23

Permeability, Diffusivity, Solubility, Selectivity

p. 492

Permeability: with JA is the flux

l is thickness of membrane

∆p is pressure drop over membrane

P = D . S D is diffusivity

S is solubility

Selectivity:

Permeability and Permselectivity of Polymers

p. 494

24

Other Membrane Processes

p. 497

Measurement of Gas Permeability

p. 507

Diffusivity D: Permeability P is proportional to steady state transport rate dQ/dt

25

Membrane Preparation

p. 510

• dense non-porous membranes:melt extrusion, compression moulding, solution casting, spin coating

• porous membranes:

Asymmetric-Membrane Formation

p. 516

Hollow fiber

Coated asymmetric membrane

Production by using phase separation techniques

1. Coating

2. Dense layer

3. Pore

4. Substrate