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Polyolefins and PVC composites with either wood
or natural fibers such as kenaf, hemp, jute, sisal or rice hulls
have been in the market for the last decade or so. Great strides
have been made, particularly in the areas of building, infrastructure,
transportation and industrial/consumer sectors. The typical applications
that have become quite popular are:
| Sector |
Products |
| Building |
Decking, Fencing, Decorative Trims |
| Infrastructure |
Boardwalks, Guard Rails |
| Transportation |
Interior Auto Panels, Truck Floors, Head Liners |
| Industrial/Consumer |
Benches, Playground Equipments, Pallets |
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While most of the initial product developments
have been in the Extrusion Sector, some efforts are being made to
develop injection-moulded products for the furniture as well as
construction and building industry (Door Components).
PP and HDPE are the major Polyolefins used for composites. PVC,
on account of its widespread usage in the building industry, provides
better weathering at a lower cost compared to the Polyolefins.
Wood as well as natural fibers require to be well dispersed in
the polymer matrix. The coupling agents such as Maleated Polyolefins
are essential not only to improve dispersion, but also reduce water
absorption and thereby enhance the long-term performance of the
composites. To provide good surface appearance, particularly at
a higher output, lubricants are essential. While the commonly available
Zn Stearate or EBS are generally used as lubricants, the newer specially
developed lubricant systems from Honeywell Specialty and Struktol
provide enhanced flow as well as improved mechanical properties
when used with the Maleated coupling agents. For outdoors applications
UV stabilizer such as HALS are essential. The most important aspect
to be taken into consideration about these natural fibers is the
prevention of growth of microbes like algae or fungi. The antimicrobial
additives available from Ciba and Rohm & Haas are generally
used in these composites to prevent physical disintegration due
to the microbial attack during the life span of the products.
The predrying of the natural fiber or the composite compounds before
conversion is absolutely essential since these natural fibers have
inherently very high level of moisture.
During the last few years several leading machinery manufacturers
like American Maplan, Cincinnati, Davis Standard etc have developed
extrusion systems specifically designed for these types of plastics-natural
fiber composites. Click
here to read more about these machineries that was described in
our earlier newsletter.
It is estimated that the market of more than half million tonnes
of these composites has already been developed by 2001. It is expected
that the demand would reach about 1 million tonne in the next 5
years.
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