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CSA > intro to polymers e lec > Flashcards

intro to polymers e lec Flashcards

definitions polymerisation properties such as shrinkage molecular mass structure thermal

1
Q

what is alginate

A

a hydrocolloid

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2
Q

give an example of a natural polymer

A

collagen

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3
Q

what is a denture material made out of

A

the vulcanisation of rubber

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4
Q

when did we see alginate impressions

A

since the second world war

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5
Q

what did we see since the second world war

A

the poly methylmethacrylate and alginate impressions and acrylic base denture resin

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6
Q

what language does the world polymer come from

A

greek

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7
Q

what does polymer mean in greek

A

many parts

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8
Q

how many carbons does ethene have

A

it has 2 carbons

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9
Q

how many hydrogens does ethene have

A

it has 4 Hs

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10
Q

what is in the ethene molecule which makes it special

A

a double bond which is relatively easy to break

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11
Q

how can we write a repeated unit of a mer

A

by adding a bracket and a n outside the bracket

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12
Q

the n is called the

A

degree of polymerisation

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13
Q

how can we calculate the molecular mass of the polymer

A

by the degree of polymerisation and the product of the molecular mass

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14
Q

what are the three types of co polymer

A

block
graft
random co polymer

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15
Q

what can co polymers do

A

tailor the properties of the final material

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16
Q

what is a straight polymer called

A

a linear polymer- a simple polymer

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17
Q

if the chain is branched off the main backbone it can resemble a

A

graft co polymer

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18
Q

if the branched polymer attaches to another it can form

A

a 3D structure which is said to be cross linked

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19
Q

what is an example of cross linking in dentistry

A

a alginate impression material

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20
Q

which type of polymer can be melted and remodelled

A

linear or branched- and they are called thermoplastic

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21
Q

what type of waxes do we use in dentistry

A

thermoplastic

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22
Q

which type of polymer does not melt and rest

A

cross linked

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23
Q

in dentistry which example do we have of a thermoset polymer

A

poly methylmetacrylate(PMAA)/acrylic

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24
Q

what is polymerisation

A

the act of reacting the monomers or comonomers into a polymer

25
Q

what are the two main branches of polymerisation

A

condensation polymer

addition polymer

26
Q

what is condensation polymerisation

A

it is where the monomer reacts to form a polymer and a small by product is produced

27
Q

what is addition polymerisation

A

it is when monomers great together but no by product is produced

28
Q

condensation polymers grow by

A

step growth

29
Q

what is the most common by product

A

water

30
Q

what can also be a by product

A

low molecular weight alcohols

31
Q

how does addition polymerisation occur

A

by a chain reaction

32
Q

name the four steps of the chain reaction

A

activation
initiation
propagation
termination

33
Q

what chemical is added to the monomer

A

the initiator

34
Q

what is the initiator sensitive to

A

heat
light
additional chemicals

35
Q

what does activation do

A

split the initiator molecule so that there are very reactive free radicals

36
Q

what does the initiation stage have

A

the very reactive free radicals which hone into the weaker points in the monomer

37
Q

what happens in the propagation step

A

the free radical binds and then gets passed on to the other monomer

38
Q

during termination

A

the free radical must either meet another free radical or join to a hydrogen

39
Q

what is it called when two free radicals join in the termination step

A

combination

40
Q

what is it called when the free radical binds to a hydrogen in the termination step

A

disproportionation

41
Q

what happens when a double bond is broken

A

heat is given out exothermic

42
Q

what are the clinical considerations for breaking a double bond

A

it can become uncomfortable for the patient

43
Q

the conversation from methyl methacrylate to polymathy methacrylate

A

can reduce in volume by 30%

44
Q

how do we reduce the volume lost

A

by using filler particles of a material that doesn’t change volume

45
Q

which particle is used in PMAA

A

particles that have been previously polymerised polymer

46
Q

what does Mm stand for

A

mean molecular mass

47
Q

what is different amount the graph

A

the graph is skewed so the mean lies funny

48
Q

how can this be fixed that the graph is skewed

A

this can be rectified by taking the “number average molecular mass” this calculates what length chain the average (mean) monomer resides in.

49
Q

what structures can polymers form

A

crystalline or amorphous

50
Q

what structure is crystalline

A

a highly ordered structure

51
Q

what structure is amorphous

A

random loose net work which is toucher

52
Q

what structure are most polymers

A

a mixture of the two structures

53
Q

this can depend on

A

chemistry and processing

54
Q

what does Tg mean

A

gasses transition temperature

55
Q

what is the temp of tg

A

lower than the melting point

56
Q

polymers below Tg are said to be

A

glassy

57
Q

polymers above Tg are said to be

A

rubbery

58
Q

the longer the chain group the

A

lower the Tg

59
Q

why does the tg become lower in the longer chain group

A

as they push the pendants far apart

CSA (51 decks)

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