Polymers and Emerging Materials

Question 1

Addition Polymerisation

Answer 1

• one carbon-carbon double bond add to another. monomers continue to react to form a chain.
• one carbon reacts to something to make a chain end and leave the other carbon reactive.
• reactive carbon reacts with another carbon double bond, forming longer chain.
• two active chain ends join together, or carbon reacts with another initiator to close chain

Question 2

Condensation Polymerisation

Answer 2

molecules join together, forming and loosing small molecules like water as byproducts.
usually involves more than one monomer species
has small molecular weight

Question 3

thermoplastic polymers

Answer 3

not chemically cross linked
soften when heated 
-polyethylene PE
-polypropylene PP
-polyvinylchloride PVC
- polycarbonate PC
- acrylics 
-polynides (nylons)
-polystyrene PS
-Bitumen (not a polymer)

Question 4

Thermosetting polymers

Answer 4

chemically crosslinked 
dont soften when heated 
need to be shaped before polymer is formed 
harder, more brittle, dimentionally stable 
-epoxies
-unsaturated polyester 
-vinyl ester 
-polyethane 
-phenolic 
-urea formaldehyde 
-silicone rubber

Question 5

crystalline

Answer 5

chains are aligned

stronger

Question 6

amorphous

Answer 6

chains are not aligned

Question 7

additives

Answer 7

used to modify properties

• fillers
• plasticizers
• stabilisers
• colourants
• flame retardants

Question 8

fillers

Answer 8

can improve:- tensile and compressive strength

• abrasion resistance
• toughness
• dimensional strength

includes: - wood flour
- silica flour
- sand
- glass
- clay
- talc
- limestone

Fillers can reduce cost

Question 9

plasticizers

Answer 9

improve strength and ductility 
reduce hardness and stiffness 
small molecules sit between large chains 
-increase inter chain distance 
-reduce inter molecular bonds 
large additions can lead to a liquid

Question 10

stabilisers

Answer 10

uv and oxidation can lead to polymer degradation
help counteract the process
complex range of materials

Question 11

colourants

Answer 11

dyes - dissolve into the polymer
pigments - remain as a phase in substance
can complicate recycling
v practical in application

Question 12

polymers in structures

Answer 12

desirable properties :- low density, less mass used
-easy shaping
good adhesion
-good thermal and electrical insulation
low duty structural components :- surfaces
-membranes (moisture control)insulation foams
-adhesive
-pipes
-grouts
-geotextiles

Question 13

polyethylene PE/ polypropylene PP

Answer 13

v similar polymers 
used in :- membranes 
-sheeting 
-pipes 
-damp proof courses 
recycles to form :- roadside furniture 
-railway sleepers 
-embankment reinforcement

Question 14

types of polyethylene PE

Answer 14

low density polyethylene (ldpe)
-chain branching 
high density polyethylene (hdpe)
-linear branching 
ultra-high molecular weight polyethylene (uhmwpe)
-greater chain linearity 
-greater chain length 
-improved physical and mech properties, more crystalline

Question 15

polyvinylchloride (PVC)

Answer 15

plasticised (flexible)
plasticised (rigid)
resistant to weathering (slight discolouration)
low maintenance requirements
durable 
good thermal insulation 
used for :- sheets 
- pipes 
-window profiles 
-interior items

Question 16

polycarbonate PC/polymethacrylade PMMA

Answer 16

mainly used as sheets for decorative or glazing purposes 
transparent but can be coloured 
PC - tougher but less transparent 
      - impact areas , roofs 
PMMA - clearer 
            - aquaria, signage 
part of acrylic fam 
- roofing tiles 
- cladding 
- adhesive 
- sealants 
-coatings/paints
-interior items

Question 17

Polystyrene foams

Answer 17

lightweight, good insulation, good moisture resistance
used in :- roof insulation 
- wall insulation 
-ceiling/attic insulation  
-geotechnical insulation 
-composite panels 
difficult to recycle

Question 18

Polymides nylon

Answer 18

commonly a fibre
good mechanical properties: -easy to form fibres
-resistance to damp, vibration or grinding
used for : - getextiles and geogrids
used in composites as structural components

Question 19

bitumen

Answer 19

naturally occurring high molecular weight hydrocarbon
residue fro oil and coal cracking
used in :- paving
- roofing applications

Question 20

epoxies

Answer 20

avalible as a resin and a hardener which then cure (polymerisation)
used as :- adhesive 
-paint 
-grouts 
-polymer matrix in composites 
v strong adhesion to many substrates

Question 21

unsaturated polyester / vinyl ester

Answer 21

similar to epoxy, but not as adhesive
-polyester is cheaper, vinyl ester stronger
both used in composite applications
vinyl esters are used in marine applications - good corrosion resistance, resist water absorption.

Question 22

polyurethane

Answer 22

used as a foam
- flexible and rigid forms
- good in insulation and upholstery packing
has good adhesion- used as coating and adhesive
flammable, flame retardants can help
not good uv radiation resistance

Question 23

phenolic foam

Answer 23

good resistance to chemicals water and temperature
excellent fire performance  
used in :- roofing 
-cavity board 
-wall and floor insulation

Question 24

urea formaldehyde foam

Answer 24

used in the past for insulation
can be easily injected
used in hard to reach places in current homes

Question 25

elastomers

Answer 25

rubber like elasticity (return to original shape )
unstressed chains are coiled and kinked, allowing for chains to straighten under stress.
cross linking is present

Question 26

silicone rubber

Answer 26

elastometric material

good adhesion conforms well to surfaces. common sealant