Polymeric Composites with Different Constituents - Introduction to Polymeric Composites with Rice Hulls - page 73

Many organisations have tried to use recycled materials to make WPC but often the
only major problem is reassurance about continued supplies over long periods of
recycled materials of adequate and consistent quality. Using recycled materials need
not necessarily reduce the quality of a final product. In China (where most of the
wastes from Western countries are welcomed, especially plastic scraps), a prominent
manufacturing company has announced the use of waste wood, waste newspaper
and magazines together with two types of plastic bottle scraps. According to their
reports, they employ an 'air-laying' (term used in the paper industry) and melt-blending
processing methods. Air-laid composites made from demolition wood wastes and
milk bottles made from PE or beverage bottles made from PE terephthalate have
properties that did not differ much from composites made from virgin ingredients.
With the melt-blending process, composites were made from waste paper, milk bottles
made from PE and battery cases or plastic ketchup bottle regrinds made from PP. The
quality of the waste-paper products were superior to the ones made with magazines
and compared well with products made from wood flour. WPC made from recycled
newspaper could itself be recycled further several times, meaning that it could be
re-extruded repeatedly with very little degradation. However, the availability of used
newspaper is not what WPC producers would like. A steady supply of used newspaper
in large quantities is very unlikely because well-established markets in wrapping and
packaging are established.
The European Union (EU)-funded SustainComp project was commissioned to
develop demonstrator products made from bio-plastics reinforced with wood fibres.
Some of the products developed were: a cushioning system for electronic devices; an
extruded component for bus seats; toy building blocks; an advertising display panel;
a compostable cutlery set for catering applications. For all of these items (except the
cutlery set), the composites developed were from starch-based bio-plastics filled with
wood fibres. Residues from heating and cooking, for example, have been suggested
to be possible raw materials for WPC products bonded with appropriate polymers.
The polymer resin component is the more expensive one, but WPC can absorb more
wood than resins and thus the cost reduction will be significant. Other important
considerations are the process ability of the raw materials and their effect on the
properties and characteristics of the finished articles.
Use of WPC for decking is by far the largest application area but the potential for
using them in other exterior and interior applications are strong. Most of the predicted
growth is expected to be in construction applications, most of which will be extruded.
Important end uses within the construction sector (besides decking) include siding;
cladding; fencing; and window applications. Injection-moulded products have been
used in diverse end uses, including paper-manufacturing applications and musical
instruments, as well as vehicle and shoe parts, whereas various other processing