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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

These are the largest molecules made of repeating parts

A

polymers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does polymer mean when broken up?

A

poly = many
mer = part

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

a long chain molecule made up of many small identical units

A

polymer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

the smallest repeating unit of a polymer

A

monomer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is an example of a monomer?

A

ethylene in polyethylene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

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

A

polymerization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What bond properties are represented by covalent bonds?

A

mechanical, thermal, photochemical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What bond properties are represented by secondary bonds?

A

physical, melting, flow, dissolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How is the molecular weight of polymers determined?

A

calculated from the molecular weights of all the chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens as molecular chains become longer?

A

mobility decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens as molecular weight increases?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

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

A
  1. linear
  2. branched
  3. cross-linked
  4. three-dimensional
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

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

A

branched polymers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

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

A

reduced –> lower polymer density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How are cross-linking polymers obtained?

A

by adding a cross-linking agent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

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

A

network polymer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How are polymers classified?

A

by type of polymers

  1. homopolymers
  2. copolymers
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

one type of monomer is used to form the polymer

A

homopolymers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

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

A

copolymers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

process which takes chemical bonds of monomer to form chains

A

polymerization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Not all monomers react during polymerization, so what is the result of this?
residual monomers trapped in the polymer
26
True or false: Polymerization may produce byproducts
true
27
What two things happen during polymerization?
1. polymer chains with different lengths formed 2. number of monomers per chain are different
28
the extent to which monomer is converted into polymers
degree of polymerization
29
This type of polymerization leads to more rigid, less soluble polymer netowrks
high degree
30
This type of polymerization has fewer longer polymer chains
high degree
31
What are the 3 chemical stages to obtain the monomer's bonding?
1. initiation --> activation of monomer 2. propogation --> chain growth 3. termination --> reaction completion
32
When does an addition polymerization begin?
when a free radical is formed
33
True or false: In addition polymerization, there is co-generation of byproducts.
False, there is no co-generation of by-products
34
What are 3 reasons why addition polymerization is preferred clinically?
1. no risk of leaching of the by-product intraorally 2. prevents increase shrinkage 3. toxic reactions to the patient
35
What is an example of polymerization?
PMMA
36
a chemical species that reacts with a monomer to form an intermediate compound
initiator
37
What do the most widely used initiators produce?
free radicals
38
What are the 3 types of initiators?
1. photo --> light 2. chemical --> chemistry 3. thermal --> heat
39
increases the speed of polymerization
accelerator
40
chemicals modify the interactions between the polymer strands
plasticizers
41
solid particles that change their optical or physical properties
fillers
42
What two things can happen when fillers are added into the polymer?
1. increase wear resistance 2. decrease shrinkage
43
What do the physical states of polymers depend on?
phase, configuration and alignment of molecular chains - amorphous - crystalline - semi-crystalline
44
True or false: polymers are rarely 100% crystalline
True
45
The temperature at which a significant loss of modulus (stiffness) or volume occurs
glass transition temperature (Tg)
46
What are 5 properties of thermoplastic polymers?
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
What are 5 properties of thermoset polymers?
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
Compare and contrast thermoplastics vs. thermoset polymers. Give 3 examples of each type.
49
Polyethylenes are available commercially as what 5 things? Which is the most common? Which is implantable?
50
What is the colour of polyethylene?
clear to whitish translucent thermoplastic
51
What are the 3 different types of polyethylene?
low = short branches high = long chain, long branches linear low = like low density, but longer branches
52
Compare and contrast HPDE (high density) and LPDE (low density)
53
What are the applications of HDPE?
pharmaceutical bottles, nonwoven fabrics, caps
54
What are the applications of LPDE?
flexible container, nonwoven disposabal and laminated foil, polymers for packaghing
55
What are the applications of LLDPE
pouches and bags due to its excellent puncture resistance
56
What are the applications of VLDPE
extruded tubes
57
This has been used for orthopaedic implant fabrications because it has superior wear properties
UHMWPE
58
What are the 3 load-bearing applications of UHMWPE?
1. acetabular cup of total hip 2. tibial plateau 3. patellar surfaces of knee joints
59
What are 5 specific properties of UHMWPE?
1. low cost 2. easy to process 3. excellent electrical insulator 4. excellent chemical resistance 5. tough and flexible (even at low temps)
60
bone loss in the vicinity of total joint prostheses caused by wear particles shed by the UHMWPE
osteolysis
61
What does osteolysis result in?
loosening of implants
62
True or false: Crosslinking has led to significantly reduced wear and osteolysis
True
63
Polymethylmetacrylate (PMMA) is best known for what 4 things?
1. biocompatibility 2. light 3. transparency 4. good weathering properties
64
What are the 4 medical applications of PMMA?
1. bone cement 2. bone pump 3. IV systems 4. contact lens
65
How is PMMA formed?
free radical polymerization - no by products, exothermic
66
acrylic or acrylic glass as well as by the trade names Crylux, Plexiglas, Acrylite, Lucite, Perspex
poly (methyl methacrylate) - PMMA
67
What are the chemical stages for PMMA initiated by?
benzoyl peroxide
68
What are 8 PMMA properties?
69
Comonomers such as ____ are often added to improve impact strength
butyl acrylate
70
Comonomers such as ___ can be added to increase the glass transition temperature
methacrylic acid
71
Crosslinking ____ and ____ can increase strength, hardness, stiffness, and creep resitance
ethylene glycol dimethacrylate
72
____ can be used to add translucency, inorganic pigments for colour and small coloured fibers to mimic blood vessels
ceramic oxide
73
Traces of _____ can be used to prevent inappropriate polyermization by room light
inhibitor (hydroquinone)