polymers

Question 1

what is condensation polymerisation

Answer 1

formation of large molecules w formation of by products, usually more than 1 monomer species, by product elimination–> small mw, slow reaction

Question 2

what is addition polymerisation

Answer 2

formation of large molecules without the formation of by products, only 1 monomer species, no change in composition. No by product elimination–> high mw, faster rxn, exothermic. There is polymerisation shrinkage–> decrease volume

Question 3

what are the stages of polymerisation

Answer 3

1. initiation
2. propagation
3. termination

Question 4

what does the initiator release

Answer 4

free radical

Question 5

what happens in the propagation stage

Answer 5

linear growth of molecules, free radical shift to end of growing chain, chain reaction continue untill all monomer converted to polymer, increases viscosity

Question 6

what can inhibit polymerisation

Answer 6

impurity in monomer which reacts with the growing chain or the initiator

inhibitors like hydroquinone, eugenol, large amount of O2

Question 7

how does larger monomer unit affect mechanical properties

Answer 7

increases mechanical properties

Question 8

how does a longer polymer chain affect mechanical properties

Answer 8

more difficult to distort as more entanglement form, increases mechanical properties

Question 9

what do plasticisers do

Answer 9

enter polymer network and break cross linkage, degrade polymer, decreases strength and glass transition temp (softening point)

Question 10

how can plasticiser exert its effect

Answer 10

external: penetrates between polymer chain increases distance betw chains decreases force betw chains

internal: copolymerisation with suitable co monomer and become part of main polymer chain