A mould release agent is applied to the mould surface to allow the composite part to be easily removed from the mould, avoiding stick-ups. Release agents may be sprayed, brushed or wiped on and some can be left on whilst others are wiped off. There are five types of mould release agents used in the composites industry:
Polyvinyl alcohol (PVA): A clear, blue or red liquid. When it dries it forms a plastic film over the surface of the mould
Wax systems: These can be a paste or liquid. These include carnauba wax and also other natural and synthetic waxes
Semi-permanent polymer systems: These are also called semi-permanent release agents and can also be called polymer release agents. These are based on one or more polymeric resins dissolved in a solvent.
Hybrid systems: These systems combine wax and polymer.
Internal release additives: These are incorporated into sheet moulding compounds and dough moulding compounds.