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Biomaterials > Intro to Polymer > Flashcards

Intro to Polymer Flashcards

1
Q

polymer aka

A

macromolecule (bigger than 5000 molecular weight)

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2
Q

two major ways to forma a long chain?

A
  1. addition

2. condensation

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3
Q

describe addition reaction

A

uses concept of free radicals

  • a way to form a long chain
  • the double bonds OPEN
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4
Q

describe condensation reaction

A

two things coming togethe (monomers) like a and b with something else (like water) getting released as they form a long chain

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5
Q

degree of polymerization refers to?

A

(n) how long the chain is and how many units you have

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6
Q

describe monomer and repeating unit with polymerization with addition mechanism

A

uses free radical polymerization and the repeating unit = the base unit where the base unit is the smallest component of the repeating

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7
Q

material used as an example in free radical vinyl polymerization

A
  1. mathy methacrylate (acyrlic) as the repeating (base unit) to poly (methyl methacrylate)
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8
Q

describe base unit in addition vs condensation

A

in addition the base unit = the repeating unit but in condensation the repeating unit is a combination of a and b

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9
Q

*list the major dental monomers used

A
  1. Bis-GMA
  2. UDMA
  3. TEGMA
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10
Q

T/F polymer molecular weight is an averaged value?

A

TRUE

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11
Q

two major polymer chain structures

A
  1. linear

2. cross-linked

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12
Q

most composites are polymerized through? importance?

A

through cross-linking

- so energy required to break the cross link is same as energy to break the linear chain

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13
Q

what is the polymer material molecular model

A

semi-crystalline model

- cystalline domain and amorphous domain

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14
Q

describe amorphous and give example

A

polymers have molecular chains arranged randomly with no long term order

*they soften rather than melt suddenly
example – polystyrene

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15
Q

describe crystalline and give example

A

polymers have a regular order or pattern of molecular arrangement so they have a SHARP melting point

example – HDPE is semi-crystalline

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16
Q

glass transition temperature unit

A

Tg

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17
Q

glass transition temperature

A

second order reaction

depends on the rate of measurment

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18
Q

what is the material like between the tg and tm

A

rubbery and more viscoelastic

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19
Q

tg vs tm

A

glass transition point vs melting point

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20
Q

major point to compare between tg and tm

A

Tg is always lower than tm

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21
Q

melting temperature with semi-crystalline?

A

there is a RANGE

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22
Q

plastic working temperature?

A

LESS THAN TG

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23
Q

rubber working temperature

A

GREATER THAN TG

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24
Q

copolymer definition

A

polymer chain made by two or more monomers

  • this is a chemical bond
25
Q

Dental composites are copolymers of?

A

Bis GMA, UDMA, TEGMA

26
Q

3 types of copolymers

A
  1. stastitical
  2. alternating
  3. AB block
27
Q

polymer MW?

A

Molecualr weight is THE AVERAGE

28
Q

major points if have higher MW

A

higher transit in temperature

  1. Higher Tm (melting)
  2. more rigid
  3. higher modulus and stress
  4. higher viscosity
  5. higher wear resistence
  6. lower solubility
29
Q

FOUR MAIN STEPS IN free radical polymerization

A
  1. induction
    - activation (fast)
    - initiation (slow)
  2. propagation
  3. termination
  4. chain transferring
30
Q

activation overview? uses?

A

part of induction (step 1)
- free radicals can be generated by activation of radical producing molecules
aka via intiators

31
Q

intitators commonly used (aka intitation system)

A
  1. heat
  2. redox reaction
  3. light
32
Q

describe heat as an iniator? major one we use?

A

commonly employed intitator is benzyl peroide (BPO) which is activated rapidly between 50 and 100 degrees celcius to release two free radicals per BPO molecule

33
Q

describe redox chemical reaction

A

consists of two reactants when mixed undergo a reaction

- like tertiary amine (activator) and benzyl peroxide (intiator)

34
Q

visible light or ultraviolet light use?

A

intiators
- generate free radicals when irradiated by light in the blue to violet region

*light wave of about 470nm is needed to trigger the reaction

35
Q

*definition and descrption of initiation

A

free radicals formed by intiator open double or triple carbon bonds in the monomer

new free radicals with monomer structure form

SLOW reaction

36
Q

slowest part of the polymerization using free radicals

A

initiation

37
Q

describe the propagation stage

A

rapid addition of monomer molecules to free radical - free electrons shifted to the end of chain

resutls in free radical complex - which acts as a new center - approached by another monomer to form a diumer

VERY FAST
EXOTHERMAL RXN

38
Q

result of propagation

A

the resulting free radical monomer complex acts as a new free radical center which is approached by another monomer to form a dimer, which also becomes a free radical

39
Q

describe chain transfer stage

A

the active free radical of a growing chain is transfered to another molecule (monomer or inacgivated polymer chain) and a new free radical for further growth is created and termination occurs in the latter

40
Q

describe termination stage

A

reaction terminates when insufficient free radicals eist

-reaction also may be stopped by any material that iwll reacti wtih free radical

41
Q

T/F termination can occur from a chain trasnfer

A

TRUE

42
Q

additiono polymeriation reaction is terminated by?

A

direct coupling of two free radical chains ends

exchange of hydrogen atom from on growing chain to another

43
Q

describe photo polymerizatoin

A

the use of a light source in the preparation of polymers

44
Q

photinitiator for UV and Blue visible light

A

UV- Irgacure 2959

Blue visible light - camphorquinone (CQ), lucirin (TPO), and phenylproanedione (PPD)

45
Q

% for most commercial dentla composite photo stimualtion

A

.5-1%

46
Q

inhibitor

A

basically opposite of initiator

completely stop the conversion of monomer to polymer prduced by accidental initiation during storage

47
Q

types of inhibitors

A

phenols, quinones, hydroxyquiones, and molecular oxygen (O2) are used to inhibit polymerization

48
Q

inhibitor often used in dental composite

A

butylated hydroxytoluene (BHT) at 0.001-0.01 wt %

49
Q

thermoset polymer has what chain structure?

A

cross-linking

50
Q

working and setting time for restorative self cure

A

working - 90 s

setting time - 5 min

51
Q

working and setting time for restorative dual cure

A

workin - 90 s

setting - 10

52
Q

working and setting time for luting material self - cure and dual cure

A

working - 60 s

setting - 10 min

same for duel cure

53
Q

T/F degree of conversion is same thing as degree of polymerization

A

false -
conversion is fraction of monomer functional group that has reacted in polymerization
- like how much monomer converts to polymer

54
Q

silicone polymer condensation

A

alcohol is released and it contributes to contraction/ shrinkage of the impression

  • ends in crossed linked polymer of silicone rubber
55
Q

additive silicone reaction? what material is this?

A

PVS - polyvinyl siloxane
- stepwise polymerization - NOT polycondensation

No small molecules released

NOT free radical polymerization

LESS shrinkage

56
Q

implication of small molecules release

A

you get a dimensional change after polymerization

57
Q

additive silicone is what type of polymerization reaction

A

poly-addition - step growth

not free radical

58
Q

definition of creep of polymer materials

A

creep is the long-term deformation of a polymer under a sustained or intermittent load at stresses below the yield point

59
Q

describe linear homopolymer vs statistical copolymer vs alternating copolymer

A

base unit = repeaating unit

statistical copolymer base unit ! = repeating unit

alternating copolymer = 2 base units = repeating unit

Biomaterials (16 decks)

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