Polymer Finishing

Question 1

Overmouldings

Answer 1

Moulding is second polymer over specific parts of a product

TPE (thermoplastic elastomer) is often used

Can provide areas of grip and texture

Can highlight different colours for different components

There are two main methods

E.g. Shaving razors have an overmoulding for grip

Question 2

Methods of overmoulding

Answer 2

Two injection moulding moulds -

one mould for the product and one mould for the grip areas.

Product is injection moulded, then placed into a second mould where the overmoulding polymer is injection-moulded onto the body

Twin-shot injection moulding -

very fast continuous cycle process

Has a mould designed to produce the product in one cycle

Two separate component cavities and can be rotated through 180 degrees so that they line up with the twin injection points

Firstly the main product part is created in the first mould cavity

The mould opens slightly and rotates 180 degrees to the secondary position

The mould closes and the second injection applied the overmould

Question 3

Acrylic spray paints

Answer 3

Acrylic paint is a fast-drying, water soluble paint that becomes water resistant when dry

Improves aesthetics, provides additional protection against the effects of UV light and weathering

Often used for mass customisation, particularly in the automotive industry - e.g. Colour coding bumpers and wing mirrors

Question 4

Polymer finishing

Answer 4

Additional finishes are sometimes applied to enhance aesthetics or improve product function

Polymers are self finishing - they require no additional finishing processes once manufactured

Question 5

Adding pigments

Answer 5

Provides colour

Can be added during manufacturing processes or during the manufacture of the polymer stock form

Smart pigments can also be added the same way - thermochromic and phosphorescent

Pigments can be added to gel coats when laying up GRP