Wood-plastic composites (WPCs) are composite materials made of wood fiber/wood flour and thermoplastic(s) such as PE, PP, PVC, or PLA.
Wood-plastic composites are still new materials relative to the long history of natural lumber as a building material. The most widespread use of WPCs in North America is in outdoor deck floors, but it is also used for railings, fences, landscaping timbers, cladding and siding, park benches, molding and trim, window and door frames, and indoor furniture. Wood-plastic composites were first introduced into the decking market in the early 1990s. Manufacturers claim that wood-plastic composite is more environmentally friendly and requires less maintenance than the alternatives of solid wood treated with preservatives or solid wood of rot-resistant species. These materials can be molded with or without simulated wood grain details.
The environmental impact of WPCs is directly affected by the ratio of renewable to non-renewable materials. The commonly used petroleum-based polymers have a negative environmental impact because they rely on non-renewable raw materials and the non-biodegradability of plastics.
The types of plastic normally used in WPC formulations have higher fire hazard properties than wood alone, as plastic has a higher chemical heat content and can melt. The inclusion of plastic as a portion of the composite results in the potential for higher fire hazards in WPCs as compared with wood. Some code officials are becoming increasingly concerned with the fire performance of WPCs.