1.5 Polymer finishing

Question 1

Give two reasons why polymers are considered to be self-finishing materials (2 marks).

Answer 1

As the addition of pigments are during manufacturing
As the surface texture is produced from the mould

Question 2

Give one example of a ‘smart’ pigment additive (1 mark).

Answer 2

Thermochromic/Phosphorescent pigment

Question 3

Give one benefit of using a gel coat in the lay-up process for producing laminated GRP (1 mark).

Answer 3

It removes an additional finishing process post manufacture

Question 4

Name the two elements that together produce a gel coat in the lay-up process for producing laminated GRP (2 marks).

Answer 4

Polyester resin
Pigments

Question 5

Give two reasons why car manufacturers use acrylic spray paints on polymer bumpers, wing mirror covers, sills and door handles; rather than just retaining the polymer base colour (2 marks).

Answer 5

As then the car can be customised
As it is more cost effective than changing the granules every production
Additional protection against UV

Question 5

Name and describe the processes used to create a manual toothbrush body or automotive rear light cluster, made from two different polymers (5 marks).]

Answer 5

OverMoulding:
2 injection moulding moulds:
One mould for the body is made and the body is then injection moulded
Then the product is placed into the other mould and the second part is injected onto the main part
Twin shot injection moulding:
Uses a mould that produces the product in one cycle
The mould has 2 compartments and is rotated through 180 degrees to line up with the 2 injection points
One part of the mould is injected then rotates by 180 degrees and applies the second part