Thermoset matrices

Question 1

What are the steps of curing?

Answer 1

1. Resin and curing agent monomers
2. Curing starts and dimers/trimers/oligomers start to form
3. Gelation occurs when fluidity is lost
4. Further reaction results in more crosslinking, improving most properties but reducing toughness

Question 2

What is the definition of shelf life?

Answer 2

• The time the unmixed, unreacted resin system can be stored without degradation’

Question 3

What is the definition of pot life or gel time?

Answer 3

’ The time the mixed resin can be handled before the viscosity increases to a point where processing is no longer possible’

Question 4

What is the order of common thermosets in increasing modulus, temp performance and cost?

Answer 4

Unsaturated polyesters
vinyl esters
epoxies
thermosetting polyimides
bismaleimides
cyanate esters
phenolics

Question 5

What are unsaturated polymers?

Answer 5

unsaturated C=C bond

Question 6

What does the resin consist of for unsaturated polyesters?

Answer 6

linear unsaturated polyester
Solvent/crosslinking agent
radical initiator

Question 7

What do unsaturated polyesters consist of?

Answer 7

Poor thermal resistance
Poor shrinkage on cure
Poor environmental resistance

Question 8

What is the structure of vinyl esters?

Answer 8

reactive groups at end of chain
C=C at end of chain
backbone phenylene rings

Question 9

What are the properties of vinyl esters?

Answer 9

tougher
better environmental resistance
reduced shrinkage

Question 10

What is the structure of epoxies?

Answer 10

most commonly used matrix for high performance
contains reactive, triangular epoxy
epoxy groups readily react with curing agent

Question 11

What are the properties of epoxies?

Answer 11

vary widely
high modulus and strength
low shrinkage
high temp resistance
good chemical resistance
highly crosslinked (aerospace)

Question 12

What is the structure and properties of cyanate esters?

Answer 12

Isocyanate NCO groups along and at end of chains
bond trimerises to create a very stable cyanurate ring C3N3
highly crosslinked structure

High cost
high temp
electrical applications
Radomes and attennas

Question 13

What is the structure of bismaleimides?

Answer 13

react through opening unsaturated C=C bond through heating
highly crosslinked
high performance
expensive
high temp performance

Question 14

What is the structure of phenolics?

Answer 14

fire resistant
nose cones for rockets
char layer prevents further burning