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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
Dental composites are copolymers of?
Bis GMA, UDMA, TEGMA
26
3 types of copolymers
1. stastitical 2. alternating 3. AB block
27
polymer MW?
Molecualr weight is THE AVERAGE
28
major points if have higher MW
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
FOUR MAIN STEPS IN free radical polymerization
1. induction - activation (fast) - initiation (slow) 2. propagation 3. termination 4. chain transferring
30
activation overview? uses?
part of induction (step 1) - free radicals can be generated by activation of radical producing molecules aka via intiators
31
intitators commonly used (aka intitation system)
1. heat 2. redox reaction 3. light
32
describe heat as an iniator? major one we use?
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
describe redox chemical reaction
consists of two reactants when mixed undergo a reaction | - like tertiary amine (activator) and benzyl peroxide (intiator)
34
visible light or ultraviolet light use?
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
*definition and descrption of initiation
free radicals formed by intiator open double or triple carbon bonds in the monomer new free radicals with monomer structure form SLOW reaction
36
slowest part of the polymerization using free radicals
initiation
37
describe the propagation stage
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
result of propagation
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
describe chain transfer stage
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
describe termination stage
reaction terminates when insufficient free radicals eist | -reaction also may be stopped by any material that iwll reacti wtih free radical
41
T/F termination can occur from a chain trasnfer
TRUE
42
additiono polymeriation reaction is terminated by?
direct coupling of two free radical chains ends exchange of hydrogen atom from on growing chain to another
43
describe photo polymerizatoin
the use of a light source in the preparation of polymers
44
photinitiator for UV and Blue visible light
UV- Irgacure 2959 Blue visible light - camphorquinone (CQ), lucirin (TPO), and phenylproanedione (PPD)
45
% for most commercial dentla composite photo stimualtion
.5-1%
46
inhibitor
basically opposite of initiator | completely stop the conversion of monomer to polymer prduced by accidental initiation during storage
47
types of inhibitors
phenols, quinones, hydroxyquiones, and molecular oxygen (O2) are used to inhibit polymerization
48
inhibitor often used in dental composite
butylated hydroxytoluene (BHT) at 0.001-0.01 wt %
49
thermoset polymer has what chain structure?
cross-linking
50
working and setting time for restorative self cure
working - 90 s setting time - 5 min
51
working and setting time for restorative dual cure
workin - 90 s setting - 10
52
working and setting time for luting material self - cure and dual cure
working - 60 s setting - 10 min same for duel cure
53
T/F degree of conversion is same thing as degree of polymerization
false - conversion is fraction of monomer functional group that has reacted in polymerization - like how much monomer converts to polymer
54
silicone polymer condensation
alcohol is released and it contributes to contraction/ shrinkage of the impression - ends in crossed linked polymer of silicone rubber
55
additive silicone reaction? what material is this?
PVS - polyvinyl siloxane - stepwise polymerization - NOT polycondensation No small molecules released NOT free radical polymerization LESS shrinkage
56
implication of small molecules release
you get a dimensional change after polymerization
57
additive silicone is what type of polymerization reaction
poly-addition - step growth | not free radical
58
definition of creep of polymer materials
creep is the long-term deformation of a polymer under a sustained or intermittent load at stresses below the yield point
59
describe linear homopolymer vs statistical copolymer vs alternating copolymer
base unit = repeaating unit statistical copolymer base unit ! = repeating unit alternating copolymer = 2 base units = repeating unit

Biomaterials (16 decks)

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