Polymers

Question 1

Natural polymer applications?

Answer 1

Collagen - artificial ligaments
Fibrin glue - bone glue
Coral substitutes - microporous bone
x-linked pericardium - artificial heart valves

Question 2

Synthetic polymer applications?

Answer 2

PMMA - lenses, bone cements
UHMWPE - bearing surfaces on artificial joints
silicones - breast implants
PGA - biodegradable sutures

Question 3

Thermoset polymers?

Answer 3

X-linked

generally polymerised in final shape

Question 4

Thermoplastic polymers?

Answer 4

not x-linked

can be moulded to shape by extrusion type processes in molten state

Question 5

Describe the two ways to make polymers (with example)

Answer 5

Addition - free radical opens double bond (PMMA)

Condensation - small molecule eliminated (nylon, PET)

Question 6

Polymer molecular weight

Answer 6

graph

higher mw, high properties

Question 7

Mechanical properties of amorphous and semicrystalline polymers

Answer 7

Graph
amorphous - rubbery, low E, reversibly extensible (due to xlinks and entanglements)
cryst - higher E, brittle

Question 8

Fatigue behaviour?

Answer 8

Graph

Question 9

What is Tm?

Answer 9

melting of the crystalline phase

Question 10

What is Tg?

Answer 10

glass transition temperature - hard and glassy to rubbery

Question 11

Effects of MW and xlinking on Tm?

Answer 11

inc MW - inc #free chains - dec Tm

inc xlinks - inc Tm

Question 12

E vs Temperature graph

Answer 12

-

Question 13

Characterisation techniques

Answer 13

MW - gel permeation chromatography
Structure - IR spec, NMR, electron microscopy
Mechanical and thermal props - dynamical mechanical anaylsis
Surface Characterisation - xray photoelectron spectroscopy