Introduction

Question 1

Name the 7 (+2) manufacturing methods for thermoplastics

Answer 1

Injection moulding, extrusion, blow moulding, rotational moulding, thermoforming/vacuum forming, calendaring, 3D printing, pultrusion, lamination

Question 2

Name the 2 manufacturing methods for thermosets

Answer 2

Compression moulding, transfer moulding

Question 3

What are the main properties of thermoplastics?

Answer 3

They are recyclable
Low melting temperature
Easy moulded
Can be melted and reshaped
low tensile strength 
soft, flexible
suffer from creep

Question 4

List examples and full names of the 7 most common thermoplastics

Answer 4

1. Polyethylene (PE)
2. Polypropylene (PP)
3. Polystyrene (PS)
4. Acrylic (PMMA)
5. Nylon (polyamides)
6. PVC (poly vinyl chloride)
7. ABS (acrylonitrile butadiene styrene)

Question 5

What are the main properties and features of thermosetting plastics?

Answer 5

Non-recyclable
stiffer, rigid
higher melting temp
higher tensile strength
Can only be moulded once
Cannot be melted and reshaped 
Good insulator of electricity and heat

Question 6

List examples and full names of the 5 most common thermosetting plastics

Answer 6

1. Phenol-Formaldehyde (PF) (Bakelite)
2. Urea Formaldehyde (UF)
3. Melamine formaldehyde
4. Polyurethanes
5. Epoxy resins

Question 7

What are the main properties and features of elastomers?

Answer 7

elastic, rubber-like
Return to original shape when stretched
Soft and flexible 
Can seal against gas and liquid 
low tensile strength 
can be thermoset or thermoplastic

Question 8

List examples and full names of the 4 most common elastomers under 2 separate titles (thermoplastics and thermosets)

Answer 8

Thermoset elastomers:

1. Vulcanized natural rubber
2. Polybutadiene (synthetic rubber)
3. Neoprene, silicone rubbers

Thermoplastic elastomers:
4. EVA, Spandex (lycra)

Question 9

Explain the structure of thermoplastics in terms of appearance, bonding and effects of heating

Answer 9

• Linear or branched chains
• Weak secondary bonds between polymer chains (Van der Waals)
• These weak bonds can be broken by heat, so the plastic becomes soft as the polymer chains slip over each other.
• When cooled, the weak forces hold the chains together again

Question 10

Explain the structure of thermosets in terms of appearance, bonding and effects of heating

Answer 10

• cross-linked chains
• Strong primary bonds between the chains and cross-links
• This lattice of strong chemical bonds makes thermosets stiffer, stronger, and more resistant to heat
• These long chemical bonds cannot be broken by heat, so the thermosets do not soften and reshape (they just burn).

Question 11

Explain the structure of elastomers in terms of appearance, bonding and effects of heating

Answer 11

• Coiled chains
• Can stretch out and return
• Thermoplastic elastomers (TPEs) can be heat-softened and re-shaped
• Thermoset elastomers have cross-links between the polymer chains so they are stiffer, stronger, and can’t be heated & reshaped

Question 12

What can some polymers have that makes them return to their original shape when heated?

Answer 12

They can have shape memory

Question 13

What is shape memory?

Answer 13

Some polymers return to their original shape when heated