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Biomaterials > Week 7 > Flashcards

Week 7 Flashcards

1
Q

What are 6 advantages of polymers?

A
  1. ease of manufacturability to produce different shapes
  2. cost
  3. desired mechanical and physical properties
  4. modification of surfaces to make them bioactive to body of biological processes
  5. low density
  6. biodegradeable
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2
Q

These are the largest molecules made of repeating parts

A

polymers

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3
Q

What does polymer mean when broken up?

A

poly = many
mer = part

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4
Q

a long chain molecule made up of many small identical units

A

polymer

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5
Q

the smallest repeating unit of a polymer

A

monomer

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6
Q

What is an example of a monomer?

A

ethylene in polyethylene

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7
Q

What is the reaction that occurs to allow bonds between monomers to form polymers?

A

polymerization

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8
Q

Polymers are primarily held by what two types of bonding

A
  1. primary covalent –> forces to form a chain and crosslinks between chains
  2. secondary bonding (van der waals & hydrogen)
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9
Q

What bond properties are represented by covalent bonds?

A

mechanical, thermal, photochemical

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10
Q

What bond properties are represented by secondary bonds?

A

physical, melting, flow, dissolution

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11
Q

How is the molecular weight of polymers determined?

A

calculated from the molecular weights of all the chains

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12
Q

What happens as molecular chains become longer?

A

mobility decreases

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13
Q

What happens as molecular weight increases?

A

less mobility of the chains (more entangled) –> higher strength –> greater thermal stability

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14
Q

What are the 4 ways which polymer chains can be arranged?

A
  1. linear
  2. branched
  3. cross-linked
  4. three-dimensional
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15
Q

In these type of polymers, the repeating units are joined end to end. There may also be extensive van der Waals and hydrogen bonding between chains

A

linear polymers

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16
Q

These type of polymers have branched side chains connected to the backbone which result from side reactions during polymersynthesis.

A

branched polymers

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17
Q

What happens to the chain packing efficiency when branches are formed within polymers?

A

reduced –> lower polymer density

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18
Q

How are cross-linking polymers obtained?

A

by adding a cross-linking agent

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19
Q

What three things can crosslinking of polymers change?

A
  1. melting temperature, strength, flexibility
  2. increase wear resistance
  3. degradation from solvents (i.e., alcohol)
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20
Q

This type of polymer has 3 active covalent bonds which forms 3-D networks and may be highly crosslinked

A

network polymer

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21
Q

How are polymers classified?

A

by type of polymers

  1. homopolymers
  2. copolymers
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22
Q

one type of monomer is used to form the polymer

A

homopolymers

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23
Q

if two types of monomers (a and B) are used in the polymerization reaction

A

copolymers

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24
Q

process which takes chemical bonds of monomer to form chains

A

polymerization

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25
Q

Not all monomers react during polymerization, so what is the result of this?

A

residual monomers trapped in the polymer

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26
Q

True or false: Polymerization may produce byproducts

A

true

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27
Q

What two things happen during polymerization?

A
  1. polymer chains with different lengths formed
  2. number of monomers per chain are different
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28
Q

the extent to which monomer is converted into polymers

A

degree of polymerization

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29
Q

This type of polymerization leads to more rigid, less soluble polymer netowrks

A

high degree

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30
Q

This type of polymerization has fewer longer polymer chains

A

high degree

31
Q

What are the 3 chemical stages to obtain the monomer’s bonding?

A
  1. initiation –> activation of monomer
  2. propogation –> chain growth
  3. termination –> reaction completion
32
Q

When does an addition polymerization begin?

A

when a free radical is formed

33
Q

True or false: In addition polymerization, there is co-generation of byproducts.

A

False, there is no co-generation of by-products

34
Q

What are 3 reasons why addition polymerization is preferred clinically?

A
  1. no risk of leaching of the by-product intraorally
  2. prevents increase shrinkage
  3. toxic reactions to the patient
35
Q

What is an example of polymerization?

A

PMMA

36
Q

a chemical species that reacts with a monomer to form an intermediate compound

A

initiator

37
Q

What do the most widely used initiators produce?

A

free radicals

38
Q

What are the 3 types of initiators?

A
  1. photo –> light
  2. chemical –> chemistry
  3. thermal –> heat
39
Q

increases the speed of polymerization

A

accelerator

40
Q

chemicals modify the interactions between the polymer strands

A

plasticizers

41
Q

solid particles that change their optical or physical properties

A

fillers

42
Q

What two things can happen when fillers are added into the polymer?

A
  1. increase wear resistance
  2. decrease shrinkage
43
Q

What do the physical states of polymers depend on?

A

phase, configuration and alignment of molecular chains
- amorphous
- crystalline
- semi-crystalline

44
Q

True or false: polymers are rarely 100% crystalline

A

True

45
Q

The temperature at which a significant loss of modulus (stiffness) or volume occurs

A

glass transition temperature (Tg)

46
Q

What are 5 properties of thermoplastic polymers?

A
  1. linear and branched structures (easy to fabricate)
  2. soften when heated, harden when cooled
  3. reversible
  4. reheating and reforming do not significantly change properties
  5. very long main chain of carbon atoms covalently bonded
47
Q

What are 5 properties of thermoset polymers?

A
  1. heat required to permanently set
  2. formed by temporary disabling of crosslinking
  3. once hardened, structure will not soften upon heating
  4. degrades or decomposed if heated at high temperature
  5. harder and stronger than thermoplastics
48
Q

Compare and contrast thermoplastics vs. thermoset polymers. Give 3 examples of each type.

A
49
Q

Polyethylenes are available commercially as what 5 things? Which is the most common? Which is implantable?

A
50
Q

What is the colour of polyethylene?

A

clear to whitish translucent thermoplastic

51
Q

What are the 3 different types of polyethylene?

A

low = short branches
high = long chain, long branches
linear low = like low density, but longer branches

52
Q

Compare and contrast HPDE (high density) and LPDE (low density)

A
53
Q

What are the applications of HDPE?

A

pharmaceutical bottles, nonwoven fabrics, caps

54
Q

What are the applications of LPDE?

A

flexible container, nonwoven disposabal and laminated foil, polymers for packaghing

55
Q

What are the applications of LLDPE

A

pouches and bags due to its excellent puncture resistance

56
Q

What are the applications of VLDPE

A

extruded tubes

57
Q

This has been used for orthopaedic implant fabrications because it has superior wear properties

A

UHMWPE

58
Q

What are the 3 load-bearing applications of UHMWPE?

A
  1. acetabular cup of total hip
  2. tibial plateau
  3. patellar surfaces of knee joints
59
Q

What are 5 specific properties of UHMWPE?

A
  1. low cost
  2. easy to process
  3. excellent electrical insulator
  4. excellent chemical resistance
  5. tough and flexible (even at low temps)
60
Q

bone loss in the vicinity of total joint prostheses caused by wear particles shed by the UHMWPE

A

osteolysis

61
Q

What does osteolysis result in?

A

loosening of implants

62
Q

True or false: Crosslinking has led to significantly reduced wear and osteolysis

A

True

63
Q

Polymethylmetacrylate (PMMA) is best known for what 4 things?

A
  1. biocompatibility
  2. light
  3. transparency
  4. good weathering properties
64
Q

What are the 4 medical applications of PMMA?

A
  1. bone cement
  2. bone pump
  3. IV systems
  4. contact lens
65
Q

How is PMMA formed?

A

free radical polymerization
- no by products, exothermic

66
Q

acrylic or acrylic glass as well as by the trade names Crylux, Plexiglas, Acrylite, Lucite, Perspex

A

poly (methyl methacrylate) - PMMA

67
Q

What are the chemical stages for PMMA initiated by?

A

benzoyl peroxide

68
Q

What are 8 PMMA properties?

A
69
Q

Comonomers such as ____ are often added to improve impact strength

A

butyl acrylate

70
Q

Comonomers such as ___ can be added to increase the glass transition temperature

A

methacrylic acid

71
Q

Crosslinking ____ and ____ can increase strength, hardness, stiffness, and creep resitance

A

ethylene glycol
dimethacrylate

72
Q

____ can be used to add translucency, inorganic pigments for colour and small coloured fibers to mimic blood vessels

A

ceramic oxide

73
Q

Traces of _____ can be used to prevent inappropriate polyermization by room light

A

inhibitor (hydroquinone)

Biomaterials (10 decks)

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