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DDS1-biomaterials > polymer chem > Flashcards

polymer chem Flashcards

1
Q

what do entanglements do

A

help hold the material together

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2
Q

when does entanglement occur

A

high molecular weight

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3
Q

polydispersity

A

weight average/number average

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4
Q

weight average equals number average

A

PDI=1 so monodisperse

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5
Q

if PDI = 2

A

polydispersed

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6
Q

which is larger? weight or number average

A

weight average

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7
Q

two things that chain branching and crosslinking do

A
  • increase MW

- change bulk properties

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8
Q

3 factors affecting polymer properties

A

chain length, branching, and crosslinking

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9
Q

plasticizers do what?

A
  • spread polymer chains apart

- facilitate slippage between chains (lubricant effect)

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10
Q

properties that can be manipulated to improve dental resins

A
  • mechanical
  • rheometric
  • thermal
  • solvation
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11
Q

factors affecting mechanical properties

A
  • interpolymer interactions
  • cross linking
  • cross branching
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12
Q

rheometric properties are about what

A

flow behaviour

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13
Q

rheometric properties can include what types of recovery

A
  • elastic

- viscoelastic

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14
Q

solvation properties: long chains dissolve fast or slow?

A

slow

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15
Q

what can affect polymer dissolution

A

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

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16
Q

polymers can be molded above what?

A

Tg (glass transition temperature)

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17
Q

temp at which an amorphous polymer goes from hard to soft

A

glass transition temp (Tg)

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18
Q

temp at which an amorphous polymer goes from disordered to ordered

A

crystallization temp (Tc)

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19
Q

temp at which a crystalline polymer goes from ordered to disordered

A

melting temp (Tm)

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20
Q

what transitions are seen in completely amorphous polymers?

A

only Tg

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21
Q

what transitions are seen in semicrystalline polymers?

A

Tg, Tc, and Tm

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22
Q

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

A

thermoplastic

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23
Q

are thermoplastic polymers reversible or irreversible?

A

thermoplastic = reversible

24
Q

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

A

thermoset

25
Q

are thermoset polymers reversible or irreversible?

A

thermoset = irreversible

26
Q

fatigue can be caused by 2 things?

A

1) cyclic loading

2) steady loading + chemically active agent

27
Q

cyclic loading is due to what?

A

crack growth

28
Q

stress intensity factor (K) is based on what?

A
  • applied stress
  • crack length
  • geometry
29
Q

first part of cyclic loading is what?

A

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

30
Q

second part of cyclic loading is what?

A

growth, due to tension, propagation of the crack

31
Q

third part of cyclic loading is what?

A

unstable growth, very rapid crack leading to failure

32
Q

coupling reactions equation

A

carboxylic acid + alcohol => ester + water

33
Q

polymer used in invisalign

A

polyurethane

34
Q

synthesis of polyurethane?

A

alcohol and isocyanate

35
Q

another name for chain growth poly

A

addition poly

36
Q

another name for step growth poly

A

condensation poly

37
Q

monomer chemical structure of chain growth poly

A

strained 3 member ring and double bond

38
Q

monomer chemical structure for step growth poly

A

di-functional monomers

39
Q

rate of initiation, propagation, and termination for chain growth

A

slow initiation

fast propagation

40
Q

rate of initiation, propagation, and termination for step growth

A

all the same rate (depends on concentration)

41
Q

increase in MW for chain growth

A

quick

42
Q

increase in MW for step growth

A

slow (and random)

43
Q

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

A

water

44
Q

part of the initiation in a chain growth poly is what

A

induction to form the reactive species

45
Q

two types of chain growth poly

A

1) free radical polymerization

2) ring opening polymerization

46
Q

monomer and RS for free radical poly

A

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

47
Q

monomer and RS for ring opening poly

A

monomer: 3 membered ring
RS: carbocation

48
Q

free radical sources for composite curing

A

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

49
Q

what is required for auto-cure

A

benzoyl peroxide (BPO) (initiator) and tertiary amine

50
Q

what is required for light cure

A

camphorquinone (CQ) - absorbs light

amine (initiator) called DMAEMA

51
Q

what happens with light curing

A

light excites electrons to form a free radical

52
Q

how does free radical poly terminate?

A

2 free radicals react with another

transfer of hydrogen

53
Q

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

A

free radical poly

54
Q

example of dentistry use for free radical poly

A

resins

55
Q

example of dentistry use for ring opening poly

A

impression materials (polyether)

DDS1-biomaterials (7 decks)

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