Thermoplastic and thermoset polymers

Question 1

What type of polymer can be repeatedly melted, shaped and cooled with little degredation of the polymer? what aspect of the polymer allows this?

Answer 1

Thermoplastic, the weak secondary bonds between polymer chains

Question 2

For semicrystalline thermoplastic polymers, which properties increase with increasing density (7)

Answer 2

stiffness, tensile strength, hardness, heat deflection, chemical resistance, shrinkage

Question 3

For semicrystalline thermoplastic polymers, which properties degrade with increasing density?

Answer 3

impact strength, ductility

Question 4

For semicrystalline thermoplastic polymers, what property remains constant regardless of how density changes?

Answer 4

weatherability

Question 5

What aspect of a high performance TP manufacture is important to of been specified?

Answer 5

it’s thermal history (thermal processing/cycles exposed during manufacture

Question 6

How can polymer crystal nucleation be enhanced, and why does this enhance it?

Answer 6

adding foreign bodies, as they act as convenient nucleation sites

Question 7

Without foreign bodies where will crystal nucleation occur?

Answer 7

on the surfaces of moulds or at impurities within a polymer melt

Question 8

How are Thermoset polymers typically recieved from the manufacturer?

Answer 8

with the crosslinking polymerisation reaction yet to be completed( can be handled in either liquid or solid form depending on the polymer)

Question 9

How is a crosslinked structure generated for a TS?

Answer 9

a solution of monomers or linear polymers must be mixed with a catalysing agent and a chemical reaction initiated

Question 10

describe the cure reaction for a TS

Answer 10

exothermic

Question 11

how is the cure reaction for a TS initiated?

Answer 11

after a period of time, with addition of heat, pressure or UV light

Question 12

With regards to Intermolecular structure, describe the states that could make up a Thermoset polymer?

Answer 12

only amorphous

Question 13

What type of bonds connect crosslinks for a TS?

Answer 13

strong covalent bonds

Question 14

What is the importance in ensuring the cure reaction is completed for a TS?

Answer 14

the better the cure the greater the density of crosslinks, the stiffer and stronger the polymer

Question 15

What measure is used to identify how far the cure reaction of a TS polymer has progressed?

Answer 15

degree of cure (symbol aplha)

Question 16

How is the “degree of cure” for a thermoset polymer defined?

Answer 16

Enthalpy released/total enthalpy to be released by reaction

alpha=0 at the start and alpha=1 at the end

Question 17

How does the degree of cure evolve over time for a thermoset undergoing a cure reaction? and what does it depend on?

Answer 17

depends on how heat is applied or removed from the curing component.
insert picture

Question 18

What is an elastomeric polymer?

Answer 18

elastomers (or rubbers) are polymers that exhibit high amounts of recoverable deformation. (elastic elongation typically > %

Question 19

Are elastomers thermoset or thermoplastic polymers?

Answer 19

both but majority are TS

Question 20

Name 5 common TS elastomers (NIBBS)

Answer 20

Natural rubber, Isoprene rubber, Butadiene rubber, Butyl rubber, Silicone

Question 21

what is the curing process that typical TS elastomers go through?

Answer 21

Volcanisation