Polymeric Composites with Rice Hulls for Extrusion - Introduction to Polymeric Composites with Rice Hulls - page 121

lubricants in use are: TPW 104 (PE), TPW 113 (PE), EBS (AcrawaxC), and Glycolube
WP-2200 (HDPE).
10.2.3 Colourants
Colourants are used to achieve aesthetically pleasing surface finishes. They also
provide a wood-like appearance and ultraviolet (UV) resistance. Suppliers of colour
masterbatches are using colourfast, highly reflective and weather-resistant pigments to
meet an increasingly demanding market. One of the biggest challenges of colourants
is colour-fading. Tests have shown that pigment levels must be ≥1-3% to overcome
colour staining from wood. Colour concentrates tailored for polymer composites
typically include a lubricant and are often customised multi-functional packages that
may include other agents: coupling agents, antimicrobials and UV stabilisers. There are
suppliers of specialised products with customised colour and additive masterbatches
for fibre-PE, fibre-PVC, fibre-PP and other combinations. One of the latest to be
introduced into the market are colours for fibre-polyolefin for colour finishes such
as teak-brown, cedar, weathered-grey and redwood, as well as many custom colour
matches in concentrates, liquids and non-dusting granules.
Clariant Masterbatches has a range of colours for tan, dark-red, grey and oak finishes
as standard masterbatches, as well as custom colours for PE; PP; PVC; and polystyrene
(PS) composites. These colourants are based on fibre contents of 30-70%. Techmer
PM has introduced colour finishes such as redwood, cedar, brown, white and black
as masterbatches, particularly for polyolefin and PVC fibre composites. While these
product ranges should cover more or less the needs of composite producers, they have
a choice of making requests other specialty colours, if required.
10.2.4 Chemical Foaming
Most composites, including PCRH, tend to be heavy and there is a keen interest in
the chemical foaming of extruded composites to reduce weight and materials. This
will naturally reduce costs in addition to improving surface appearance, increasing
processing speeds as well as ease the sawing, nailing, screwing and painting of finished
products, if necessary. It is estimated that ≈30% of all fibre composites produced
are foamed.
Endothermic (heat-absorbing) and exothermic (heat-giving) CFA can be used. Foaming
is more difficult for crystalline polymers such as PE and PP than for amorphous
polymers such as PVC and PS because the latter generally have better melt strength. As
a rule, the higher the fibre content in a composite, the more difficult it is for foaming