Thermosetting polymers and elastomers

Question 1

Form of supply of epoxy resins

Answer 1

Supplied as two parts:
- One resin
- One hardener
They combine to make an extra-strong adhesive
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Question 2

Properties of epoxy resins

Answer 2

• Strong, tough and rigid
• Durable
• Good chemical and thermal resistance and stability
• Good electrical insulator
• Good adhesive

Question 3

Where epoxy resins are used

Answer 3

• Cheaper and faster than welding (metals and plastics)
• General-purpose adhesives
• Rigid foam
• Laminates
• Container linings
• Waterproof coatings
• Panels

Question 4

Form of supply of polyester resins

Answer 4

Supplied as two parts:
- One resin
- One hardener
They combine to make an extra-strong adhesive
- It sets clear and smooth

Question 5

Properties of polyester resins

Answer 5

• Viscous
• Low density
• Adhesive
• Strong odour and toxic fumes
• Water-resistant
• Good wear resistance
• Heat resistance and a good insulator
• Strong and tough
• Weaker than epoxy resin

Question 6

Uses of polyester resins

Answer 6

• Adhere body panels of vehicles eg boat hulls, motor panels, aircraft parts
• Packaging
• Waterproofing and encasing items
• Laser printer toner
• Combined with fibreglass to make GRP (eg for skis)
• Fishing rods

Question 7

How does urea formaldehyde come?

Answer 7

• Limited colours
• Opaque
• Smooth finish

Question 8

Properties of urea formaldehyde

Answer 8

• Very high tensile strength
• Low water absorption
• High surface hardness. Scratch resistant
• Brittle and rigid
• Very good insulator
• Heat resistant
• Easily injection moulded

Question 9

Uses of urea formaldehyde

Answer 9

• Plug sockets and electrical appliances and fittings that are safe to use
• -> knock-resistant (hard/tough); insulator
• Adhesive for binding interior plywood and particleboard
• Treating textile fibres (better wrinkle/shrink resistance, higher surface hardness for coating)

Question 10

Properties of melamine formaldehyde

Answer 10

• Brittle
• Food-safe, dust-free surface (hygienic)
• Printable surface
• Excellent insulator
• Low water absorption
• Can be cast and moulded
  Similar to urea but
• Better moisture and heat resistance
• Harder and stronger (one of the hardest plastics)

Question 11

Appearance of melamine formaldehyde

Answer 11

• Very smooth surface finish

Question 12

Uses of melamine formaldehyde

Answer 12

• Laminates (smooth surface and hygienic)
• Electrical plugs, sockets and light switches
• Pan handles
• Adhesive for particleboard or plywood
• Household crockery/tableware eg glasses, plates, cups, bowls

Question 13

Source of rubber

Answer 13

Latex from rubber tree

Question 14

Forms of supply of rubber

Answer 14

• Bars
• Sheets
• Tubes

Question 15

Typical properties of rubber

Answer 15

• High elasticity
• Contracts with heat
• Malodour
• Water resistant
• Abrasion resistant

Question 16

Common applications of rubber

Answer 16

• Tyres and tubes for vehicles eg car, bike, lorry
• Shock absorbers for buildings
• Seals
• General goods eg balloons, rubber bands

Question 17

Source of neoprene

Answer 17

Polychloroprene, which comes from crude oil and chlorine

Question 18

Forms of supply of neoprene

Answer 18

A synthetic rubber

• Sheets
• Foam
• Extruded neoprene

Question 19

Properties of neoprene

Answer 19

• Resistant to heat, cold, flame, oil
• Resistant to weathering and chemicals (inert)
• Bonds well with other materials
• Flexible and holds its shape over time
• High tensile strength

Question 20

Applications of neoprene

Answer 20

• Corrosion-resistant coatings
• Power transformers (fire resistant)
• Safety equipment eg gloves
• Padding and packaging