Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biomaterials > Week 10 - Biopolymers > Flashcards

Week 10 - Biopolymers Flashcards

1
Q

How are polymers made?

A

By linking together small molecules using covalent bonding along backbone

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

What affects the physical properties of polymers?

A

Their chemical composition, particularly molecular weight, functional groups and side chains

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

What effect does the length of the polymer chains have?

A

On the mechanical properties, due to the entanglements between chains and their mobility

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

What forms can polymers be fabricated into?

A
  • Solid polymer parts

- Fibres for composites

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

What are the three main types of polyethylene?

A
  • Low density (soft)
  • High density (stronger)
  • UHMWPE which is the toughest most wear resistant polymer known to mankind
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the advantages of UHMWPE?

A
  • High stability
  • Low toxicity
  • Stiff
  • Strong
  • Easily produced
  • No additives or leachants
  • Low friction coefficient
  • AMAZING wear resistance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the disadvantages of UHMWPE?

A

Can fail by fatigue and creep, inflexible processing (must be compression moulded and machined), can absorb fluid and is hard to injection mould

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are methods for enhancing polyethylene wear resistance?

A

Carbon fibre, cross-linking, vitamin E

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

What are polyethylene fibres?

A
  • Fabric woven from solvent spun UHMWPE

- Can be hotpressed with a HPPE or LDPE matrix to make bullet proof panels

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

What is the strength of polyethylene fibres?

A

120GPa, but modulus can be engineered directly to match bone

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

What is polyether ether ketone?

A
  • Expensive
  • High melting point
  • Very bioinert
  • Similar properties to PTE
  • Used almost exclusively for spinal fusion cages
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is PMMA?

A
  • Thermoset which comes as two parts that can be combine via curing
  • Often used for dental materials and bone cement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the advantages of PMMA?

A
  • Outstanding bond strength

- Many different mixing methods are used to prevent porosity and minimise shrinkage

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

What are the disadvantages of PMMA?

A
  • Deterioration over time
  • Potential for leachants and wear particles
  • Sets rapidly, heating to 70 degrees, causing potential necrosis
  • Precoatings required for bonding to metal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What elastomers have been used for implants?

A
  • Silicon used when large recoverable deformations at low stress are required e.g. wrist and finger joint, breast implants
  • However absorbs blood lipids and causes swelling means no longer applicable for ball in cage valves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What natural polymers have been used for implants?

A
  • Cellulose for dialysis membranes

- Collagen for dialysis membranes

17
Q

What have synthetic polymers been used for?

A
  • Dacron for composites and on surface of blood interfacing implants
  • Hydron for breast implants, soft contact lenses and wound coverings
18
Q

What are hydrogels used for and why?

A
  • Opthalmic devices
  • Spinal disc nucleus implants
  • Very soft but difficult to sterilise
19
Q

What are biodegradable biopolymers used for and why?

A
  • Mainly used in sutures and TE scaffolds
  • Degradation products are acidic monomers which cause inflammatory response
    e. g. PGLA
20
Q

What are the factors affecting the lifespan of biopolymers?

A
  • Can deteriorate due to chemical, thermal and physical factors
  • In vivo environment may cause polymers to degrade after implantation due to ionic attack, dissolved oxygen
  • Mechanical effects can also cause polymer degradation
21
Q

What sort of chemical affects impact polymers and how?

A
  • Depolymerisation, chain scission and loss of cross linking

- Can affect mechanical properties

22
Q

What are the implications of sterilisation for biopolymers?

A
  • Anything that can kill bacteria can damage polymers

- Causes changes to polymer’s structure, inducing early deterioration

23
Q

What does heat sterilisation involve?

A
  • High temperatures and pressures

- Can take polymers above their melting or softening points

24
Q

What does chemical sterilisation involve?

A

Can cause chemical reactions in polymer and induce degradation

25
Q

What does radiation sterilisation involve?

A

Can break polymer chains and therefore change mechanical properties

Biomaterials (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions