Polymeric Composites with Rice Hulls for Extrusion - Introduction to Polymeric Composites with Rice Hulls - page 123

spheres of silica, which can be used as fillers in many plastic compounding operations.
3M/Zeelan Industries offers hollow glass microspheres, which have interesting
applications as fillers. These tiny microspheres reduce viscosity; lighten weight; reduce
costs; enhance properties; and form a barrier against moisture.
10.3 Extrusion of Polymeric Composites with Rice Hulls
Extrusion has been discussed in detail in previous chapters, so I will not dwell too
much on it other than to say that extrusion comprises the drying of rice hulls followed
by particle reduction and compounding with the polymer matrix and additives. This
mixture is then processed through an extruder, with the extruder head having a profiled
die of choice. The extrudate coming out of the die will then undergo cooling and
be cut into desired lengths by a cutting system downstream, which can be operated
manually, semi-automatically or automatically.
In the composite industry, WPC is the general term applied for composites with
wood fibre, rice hulls or others. This may be because whichever fibres are used in a
composite combining a polymer matrix and natural fibres, the resulting end products
resemble and feel like wood. When WPC first appeared on the market, they showed
very interesting possibilities as new materials with worldwide market potential.
Awareness that the use of other natural fibres was also feasible as a possible substitute
for natural wood applications made some of the top plastic engineering machinery
manufacturers (e.g., Reifenhauser , Cincinnati Milacron , Maplan Corporation ,
HardenIndustriesLtd .) begin to develop standard and tailored WPC extrusion
solutions. One of the major breakthroughs is extrusion systems for PCRH, the
products of which are superior to any in the market so far. These suppliers of
extrusion systems not only supply suitable systems but also provide full technology
and work closely with customers to ensure successful and profitable ventures.
Although composites with rice hulls stand out among the others, systems are now
available for polymeric composite mixtures with all kinds of natural fibres. In this
context, fibre quality with regard to size and moisture content can have an enormous
effect on the entire extrusion process. The following basic features are important:
• Average size of ibre (mm)
• Distribution of ibre size
• Average moisture content of mass (%)
• Fibre type (name of plant or tree)