Colouring of Polymers and Composites - Introduction to Polymeric Composites with Rice Hulls - page 104

Split-complimentary colour schemes are variations of the complimentary colour
schemes. In addition to the base colour, two other colours adjacent to its complement
are used. This colour scheme has the same strong visual contrast as the complementary
colour scheme but has less tension.
8.2 Masterbatches
Masterbatches are colourants and/or additive concentrates for plastics or synthetic
materials that incorporate a level of colourant, (in)organic pigment, pigments
to cause special effects, or additives that are higher than those found in the final
product. A masterbatch is used to proportion these additives into a larger batch
during compounding. Most thermoplastic polymers are used in a particulate structure
because this permits considerably less pollution during the process. It also allows for
easier and faster assimilation. Manufacturers choose to supply masterbatches in the
form of granules for colour uniformity and final colour requirements in keeping with
international colour codes and standards.
Some additive masterbatches may contain mineral filler compounds, for example,
mineral fillers for modifications of resins such as polyethylene (PE) or polypropylene
(PP), with significant ones being calcium carbonate (CaCO 3 ) and barium sulfate
(BaSO 4 ). Previously, most fillers were valued for their economic factor but
appreciation for mineral fillers has increased as their influence on the functionality
and physical properties of plastic products has become more apparent. Using
fillers, the density, weight, anti-block and dampening properties of a polymer can
be changed easily.
8.3 Liquid and Solid Colourants for Polymer Composites
Different systems are being used and this is related to the use of a liquid colourant
system comprising at least one pigment and one dye for colouring cellulose polymer
composites.
Cellulose polymer composites, in particular lignocellulose polymer composites (e.g.,
with rice hulls and wood fibres) have the properties of wood and plastic. They are
more advantageous because they can be produced even from recycled raw materials.
They are gaining in interest due to their potential applications, especially in high-end
industrial uses such as building construction, automobile and aviation. The cellulose
particles used in polymer composites may have different morphologies and accordingly
different largest particle diameters ranging from ≈1-10 mm (shavings), to 0.1-1 mm
(fibres) to 0.01-0.1 mm (flour). In theory, the finer the cellulose particle, the greater is