Wood Plastic Composites (WPCs)
Wood plastic composites (or WPCs) have developed from simple extrusions of planks (in the 1990s) to a wide range of products. These include cladding and decking profiles, but also injection moulded items ranging from post caps, bird feeders and plant pots up to high performance audio speakers and car parts.
The material is formed by blending wood flour or wood fibre (the properties achieved vary depending on the quantity and choice of fibre) with various of the commodity plastics such as polypropylene, polyethylene or PVC. Other plastics with higher melting points can only be used with clever consideration of equipment and feed rate to avoid scorching the wood component, but examples based on PMMA and some grades of nylon exist.
The obvious overlap with wood products is two-fold: wood fibre and wood flour from sawmill residues and other processing can be used as the feedstock; and the planks and profiles formed of WPC enter the same market as timber - e.g. decking, cladding and sometimes window joinery. Here light-weighting is key, as the WPC material itself weighs more than most timbers, so profiles with hollow centres, or foamed cores are often prepared. Care should be taken for exterior applications to buy a product which includes antimicrobial agent as fungi can still access the wood fibre within the composite if it is unprotected.