Plastics

Question 1

Give three examples of synthetic plastics

Answer 1

• Polypropylene – used in buckets, rope, clothing and chairs.
• Polycarbonate – a rigid and hard plastic used instead of glass and aluminium, because of its impact resistance.
• Polyester – used widely in the clothing industry. A versatile fabric which is combined with nylon.

Question 2

How are synthetic plastics developed into products?

Answer 2

• Crude oil is extracted from the seabed.
• Oil is heated in a fractioning tower, and broken down into chemicals. - Chemicals are used to make plastic.
• Heat and pressure are applied to the plastic to shape it.
• Product is made.

Question 3

Monomers combine to form chains of molecules called polymers. What happens as a polymer grows?

Answer 3

Its melting point increases and it becomes more rigid because of the links between each monomer molecule.

Question 4

Describe thermoplastics

Answer 4

• They are mostly recyclable.
• They can be shaped and reshaped on the heat.
• They have plastic memory.
• They are made of a long polymer chains that have few cross links making them flexible under heat.

Question 5

Describe thermosetting plastics

Answer 5

• They are initially set by heat.
• They cannot be reshaped once set.
• They are extremely durable and strong.
• They are common in powder or resin forms.
• They consist of polymer chains with the strong bonds between each chain. This is more a more rigid structure than a thermoplastic and heat improves the strength of the links.

Question 6

Name three thermoplastics

Answer 6

• High density polythene
• Polypropylene
• Acrylic

Question 7

Name three thermosetting plastics

Answer 7

• Epoxy resin
• Urea formaldehyde
• Phenol formaldehyde.

Question 8

Name three stock forms of plastic

Answer 8

Powder, granules and sheets.

Question 9

Name three additives and how they change the properties of a plastic

Answer 9

• Pigments – add colour to plastic.
• Plasticisers – make plastic less brittle and hard.
• Lubricants – improve the flowing quality making it easier to form.

Question 10

When is vacuum forming used?

Answer 10

When identical products need to be mass produced.

Question 11

How does injection moulding work?

Answer 11

This involves heating plastic granules to their melting point and then injecting them at high pressure through a nozzle into a mould.

Question 12

How does blow moulding work?

Answer 12

This involves a mould closing and sealing a thin plastic tube called a parison. It also cuts to the required length.

Question 13

Why do plastics require little to no surface finish?

Answer 13

They are self finishing and have excellent surface qualities.

Question 14

Give three examples of natural plastics

Answer 14

Shellac – a resin produced by trees, used as a varnish and die.
Rosin – used as a resin to give grip to the bow of a string instrument such as a violin.
Bitumen – used as waterproof rendering for houses, roads and boats.