Manufacturing of Polymeric Composite Resins - Introduction to Polymeric Composites with Rice Hulls - page 111

9 Manufacturing of Polymeric Composite

Resins

9.1 Concept

Over the past decade, plastics have been replacing traditional materials and have
spread quickly to cover domestic, industrial, and engineering sectors. They are even
used in high-tech applications such as air travel and space travel. Hence, the need
for newer and stronger plastics has prompted research and development to produce
high-grade polymer resins to meet these demanding challenges.

Due to increasing global environmental concerns and rising costs of polymer resins,
the plastics industry has been searching for alternatives for polymer resins, most of
which are based on petroleum. For some time now, wood plastic composites made
from polymers as the matrices and wood chips and wood flour as the reinforcing
constituents have been used first in extruded form and then to injection-moulded
and compression-moulded forms. Although the products from these composites
have proved to be practical and to compare favourably with traditionally produced
products made from pure or recycled materials, issues such as warping, exposure to
weather, and durability need to be solved. The advent of polymeric composites with
rice hulls (PCRH) has elicited superior products while overcoming these problems.

9.2 Manufacturing Process in Brief

Technology for manufacturing PCRH is fairly new and the initial product results are
very encouraging. The possibilities with these versatile composite resins are vast and are
proving PCRH to be suitable for even high-tech applications. Basically, a polymer resin
such as polyethylene (PE), polypropylene (PP) or polyvinyl chloride (PVC) is used as the
matrix and mixed with rice hull fibre or, preferably, in the form of flour (finely ground
powder) and a combination of additives depending on the end application targeted. The
polymer matrix can be virgin resin, recycled material or a combination of both, whereas
the rice hulls must be moisture-free and the particle size reduced from its original state.
Additives can take the form of: ultraviolet (UV) stabilisers; coupling agents; heat stabilisers;
or lubricants. Colourants and other surface agents are added if it is necessary to obtain
coloured or aesthetically pleasing finishes. Rice hulls are sieved, dried thoroughly to
remove moisture, reduced to a fine powder form (preferably) and then compounded with
a heated polymer matrix. This polymer mass may consist of virgin material or recycled
material or a combination of both. Carefully selected additives are then added to this