The paint selection is determined by the desired decorative effect, the
functional demands, the application technique and local regulatory
restrictions. A variety of paints have been developed, based on different
chemistries and polymers. The following generic paint types can be
distinguished.
- Acrylic paints give a brittle, scratch resistant coating and resist most
common oils. Transparent acrylic coatings (compact discs) can be applied for
UV-protection.
- Epoxy paints typically provide a hard, tough and
glossy coating.
- Formaldehyde/alkyd resins
- Polyester
- Polysiloxane coatings have good chemical and scratch resistance. Transparent
types with glass-like optical properties and good UV-protection have been
developed.
- Polyurethane paints are flexible cold-curing coatings.
- Vinyl paints typically produce a soft, rubbery coating.
Paints can be divided into two main groups: conventional paints with an
organic solvent and waterborne paints. Paints based on organic solvents
generally have better adhesion to substrates than waterborne paints, but
solvents may attack the substrate and cause stress cracking. Waterborne paints
have superior properties in relation to environmental, health and safety
matters.
Curing of the paint can take place in several different ways:
- Air-curing paints harden due to the evaporation of the solvent, while the
resin polymerizes.
- Heat-curing paints require elevated temperatures
for curing. The use of these paints systems is limited by the high curing
temperature that the plastic must be able to withstand.
-
Two-component paints have the big advantage that no volatile components
evaporate during curing. Pot-life after mixing is however limited.
-
UV-curing paints.
- Oxygen-curing paints.
Paint systems should always be tested on prototype parts over an extended
period of time, to establish the compatibility of the paint.
