Composite Technology - Introduction to Polymeric Composites with Rice Hulls - page 40

3.3.9 Aesthetic Properties
With PCRH, it is possible to achieve very pleasing finishes. Some composite
end-products will need a glossy finish, whereas others require a matt finish. These end-
products can be achieved by suitable additives and, in the case of extruded products,
the extrusion die/system will play a key part in this aspect. In injection moulding
and compression moulding, the mould surfaces will also have a key role on the type
of finish. With regard to colour, virtually any colour is possible but starts with good
homogenous mixing processes to ensure (i) blending of the rice hulls with the matrix
and base additives, and (ii) uniform absorption of the pigments or dyes (whether they
are in the form of powder, liquid or masterbatches). Special colour and grain effects
can be achieved by special additives and a combination of pigments and dyes of
different colours. Some producers of polymeric composites (especially lumber) may
opt for a protecting coating or lamination to protect the surface.