Manufacturing of Polymeric Composite Resins - Introduction to Polymeric Composites with Rice Hulls - page 114

as processing aids. In the manufacture of PCRH, one must remember that, due to
silica in rice hulls, the composite mixture is abrasive and generates extra heat in the
extruder barrel. Certain special additives may have to be incorporated into the mix
to counter these effects. Numerous additives as well as suppliers and producers of
composites will have no problems in getting what they want. In fact, a close working
relationship with them would greatly help a producer to work out the best additives
(or combinations of additives) to use to get the best results. Additives can be in the
form of solids, powders or liquids, and some may even be coupled with a particular
resin, which will greatly help in compounding. Some of the important areas in which
additives are needed to improve or enhance polymeric composites are: compatibility;
heat stabilisation; moisture control; anti-UV action; mechanical, chemical or physical
properties; light weight; durability; and easy processing.
Basic additives that are used commonly are:
• Lubricants
• Stabilisers
• Anti-UV agents
• Flame retardants
• Coupling agents
• Anti-fungal and microbial agents
• Blowing agents
• Surface inish agents
• Colourants
9.4 Processing Machinery and Equipment
The complete process can be categorised into five main operations: drying and removal
of moisture from the rice hulls; particle-size reduction; compounding; extrusion in the
form of strands; cooling and pelletising. The first three phases can be done separately
with individual equipment but a producer may opt for an in-line complete processing
extrusion/pelletising system. From the previous chapters, the reader will have a
good knowledge of the equipment for drying, particle-size reduction, and extrusion.
However, for the benefit of the reader, I present below a complete system made with
technology by an American company, HardenIndustriesLtd ., based in China and