Rice Hulls for Composites - Introduction to Polymeric Composites with Rice Hulls - page 61

and other manufacturing costs. Since the arrival of composite resins with rice hulls,
moulders, though very interested, have been showing caution in using these resins (as
with any new material). As the research and development of these composite resins
continues, moulders who have already started using these resins can do so with more
confidence. Here, I would like to recommend that the use of rice hull ash (grey state)
or a combination of ash and rice hull flour would result in better-quality composite
resins. Currently, these composite resins are being used only for extrusion, injection
moulding and compression moulding, but it is expected that they will be used for
other areas of plastic mouldings as well.
5.4.2 Animal Feed Industry
Rice hulls as a recyclable resource have many useful applications in the poultry and
animal farming industries. In the former, they are used primarily as bedding for
poultry and also as feed mix. In the animal feed industry, they are used as a fibre
source, premix and pellet binders. Rice hulls are offered by specialty producers as
different grades and grinds. The three main grades are 20/80 and 30/80 (rough) and
80. Typically, rough grind is used as a fibre source in animal feed, 20/80 and 30/80
are used as a premix animal feed, supplements and 80 grade as a pellet binder, and
unground hulls are used as bedding for animals and poultry.
5.4.3 Lumber from Composites
Rice hull flour (finely ground hulls) is an ideal composite material for polymeric
composites. Processing involves the mixing and compounding of plastic resins with
rice hull flour with additives such as fillers, lubricants, binders, and colours depending
on the end result desired, and then using an extrusion process to produce profiled
lumber. Depending on the type and size of the extrusion system, there will be limits
to the size of the profile section and width that can be produced, but lengths carry
few limitations. These products are ideal substitutes for natural wood, and reports
after testing and usage reveal many excellent and beneficial properties.
5.4.4 Building Materials
Rice hulls are class-A thermal insulating materials because they are difficult to burn
and resist penetration by moisture (which stops the propagation of mould or fungi).
Tests have shown that if they are burned, rice hulls will produce a significant amount
of silica. Rice hulls are also a potential source of amorphous reactive silica. If burned
completely, the ash can have a Blaine number (particle size) of ≤3,600 as compared