12 Polymer Processing

Question 1

types Polymer processing

Answer 1

• Solution casting of films
  – Melt-fabrication of films
  – Fabrication of fibers
  – Injection molding
  – Thermoforming
  – Blow molding

Question 2

Solution casting of film

Answer 2

• Commonly used in research settings
• small,
  thin films

The dissolved polymer is
placed on a flat substrate and:
– The solvent is allowed to evaporate (drop
coating), OR,
– The substrate is spun at high speeds (spin
coating).

Question 3

Drop coating

diff spin drop in produced polymer?

Answer 3

drops polymer dissolved in solvent, dry, uneven film

Spin coating more uniform, smaller then drop coating

Question 4

What to worry about in drop coating

Answer 4

Solubility in range solvents, BP solvent

Question 5

control film thickness?-

Answer 5

changing polymer conc in drop/spin coating

• spin: change spin speed

Question 6

Melt-fabrication of films

Answer 6

• for large films
  -polymer
  melted and extruded through rollers

Question 7

Fiber extrusion

Answer 7

Polymer is melted and
extruded through a
spinerette.

The fibers are
then cooled and stretched
on a roller.

Alternatively the
polymer is dissolved and
extruded through a
spinerette while the solvent
is evaporated using hot air.

most important: polymer MP, viscostity, mechanical strenth

Question 8

Fiber extrusion – Electrospinning

Answer 8

A small droplet of
polymer solution is
extruded from a needle
to a grounded mat by
means of a potential
field.

A film of
nanometer size fibers
are obtained using this
technique

Question 9

Injection molding

Answer 9

A melted polymer is injected into a mold and
cooled below its liquefaction temperature.

This
is a rapid mass manufacturing processes.

important: polymer MP, Viscosity, mechanical strength

Question 10

Thermoforming

Answer 10

A softened sheet of polymer is pressed into a
mold.

Thermoforming can be performed under
high pressure conditions (top) or under vacuum
(bottom)

Question 11

Blow molding

Answer 11

A softened or melted preformed material is
molded by exposing it to high pressures. Plastic
bottles are prepared in this way.

Question 12

Polymerization + Fabrication

Answer 12

A polymer can be synthesized and formed at the
same time.

• Plexiglas is produced by adding
  MMA to two parallel glass plates before starting
  polymerization.

Question 13

Blowmolding/thermofolding need polymer to be ______

Answer 13

Processed

• Blow: 3D cavity generally made by injection molding
• thermomoulding: sheet