polymer chem

Question 1

what do entanglements do

Answer 1

help hold the material together

Question 2

when does entanglement occur

Answer 2

high molecular weight

Question 3

polydispersity

Answer 3

weight average/number average

Question 4

weight average equals number average

Answer 4

PDI=1 so monodisperse

Question 5

if PDI = 2

Answer 5

polydispersed

Question 6

which is larger? weight or number average

Answer 6

weight average

Question 7

two things that chain branching and crosslinking do

Answer 7

• increase MW

- change bulk properties

Question 8

3 factors affecting polymer properties

Answer 8

chain length, branching, and crosslinking

Question 9

plasticizers do what?

Answer 9

• spread polymer chains apart

- facilitate slippage between chains (lubricant effect)

Question 10

properties that can be manipulated to improve dental resins

Answer 10

• mechanical
• rheometric
• thermal
• solvation

Question 11

factors affecting mechanical properties

Answer 11

• interpolymer interactions
• cross linking
• cross branching

Question 12

rheometric properties are about what

Answer 12

flow behaviour

Question 13

rheometric properties can include what types of recovery

Answer 13

• elastic

- viscoelastic

Question 14

solvation properties: long chains dissolve fast or slow?

Answer 14

slow

Question 15

what can affect polymer dissolution

Answer 15

Mw, pdi, crosslinking, crystallinity, chain branching, adsorbed molecules

Question 16

polymers can be molded above what?

Answer 16

Tg (glass transition temperature)

Question 17

temp at which an amorphous polymer goes from hard to soft

Answer 17

glass transition temp (Tg)

Question 18

temp at which an amorphous polymer goes from disordered to ordered

Answer 18

crystallization temp (Tc)

Question 19

temp at which a crystalline polymer goes from ordered to disordered

Answer 19

melting temp (Tm)

Question 20

what transitions are seen in completely amorphous polymers?

Answer 20

only Tg

Question 21

what transitions are seen in semicrystalline polymers?

Answer 21

Tg, Tc, and Tm

Question 22

polymers that are heated above Tg to be reshaped many times?

Answer 22

thermoplastic

Question 23

are thermoplastic polymers reversible or irreversible?

Answer 23

thermoplastic = reversible

Question 24

polymers that undergo chemical change above Tg and dont become soft again

Answer 24

thermoset

Question 25

are thermoset polymers reversible or irreversible?

Answer 25

thermoset = irreversible

Question 26

fatigue can be caused by 2 things?

Answer 26

1) cyclic loading | 2) steady loading + chemically active agent

Question 27

cyclic loading is due to what?

Answer 27

crack growth

Question 28

stress intensity factor (K) is based on what?

Answer 28

- applied stress - crack length - geometry

Question 29

first part of cyclic loading is what?

Answer 29

initiation, due to shear forces, needs to pass a threshold

Question 30

second part of cyclic loading is what?

Answer 30

growth, due to tension, propagation of the crack

Question 31

third part of cyclic loading is what?

Answer 31

unstable growth, very rapid crack leading to failure

Question 32

coupling reactions equation

Answer 32

carboxylic acid + alcohol => ester + water

Question 33

polymer used in invisalign

Answer 33

polyurethane

Question 34

synthesis of polyurethane?

Answer 34

alcohol and isocyanate

Question 35

another name for chain growth poly

Answer 35

addition poly

Question 36

another name for step growth poly

Answer 36

condensation poly

Question 37

monomer chemical structure of chain growth poly

Answer 37

strained 3 member ring and double bond

Question 38

monomer chemical structure for step growth poly

Answer 38

di-functional monomers

Question 39

rate of initiation, propagation, and termination for chain growth

Answer 39

slow initiation | fast propagation

Question 40

rate of initiation, propagation, and termination for step growth

Answer 40

all the same rate (depends on concentration)

Question 41

increase in MW for chain growth

Answer 41

quick

Question 42

increase in MW for step growth

Answer 42

slow (and random)

Question 43

loss of a water molecule is observed in what type of polymerization?

Answer 43

water

Question 44

part of the initiation in a chain growth poly is what

Answer 44

induction to form the reactive species

Question 45

two types of chain growth poly

Answer 45

1) free radical polymerization | 2) ring opening polymerization

Question 46

monomer and RS for free radical poly

Answer 46

monomer: double bond with vinyl group RS: free radical (acts as the initiator that becomes 2 R*) I->2R*, process required heat or light

Question 47

monomer and RS for ring opening poly

Answer 47

monomer: 3 membered ring RS: carbocation

Question 48

free radical sources for composite curing

Answer 48

1) auto-cute 2) light-cure 3) UV cure 4) dual cure

Question 49

what is required for auto-cure

Answer 49

benzoyl peroxide (BPO) (initiator) and tertiary amine

Question 50

what is required for light cure

Answer 50

camphorquinone (CQ) - absorbs light | amine (initiator) called DMAEMA

Question 51

what happens with light curing

Answer 51

light excites electrons to form a free radical

Question 52

how does free radical poly terminate?

Answer 52

2 free radicals react with another | transfer of hydrogen

Question 53

acrylate resins such as methyl methacrylate use what type of poly?

Answer 53

free radical poly

Question 54

example of dentistry use for free radical poly

Answer 54

resins

Question 55

example of dentistry use for ring opening poly

Answer 55

impression materials (polyether)