Forest Products Extension

Durability of wood plastic composites

Wood-plastic composites (WPCs) are a combination of wood flour (or other natural materials such as rice husks) and plastic shaped into decking lumber. WPCs are a relatively new product and are often better known by their various brand names – eg. Trex, ChoiceDek, Eon or SmartDeck – or as “composite lumber.” WPCs can be manufactured in a variety of colors, shapes and sizes, and with different surface textures. Lumber made entirely from plastic with no wood flour added – “plastic lumber” – is also available.

WPCs are expensive compared to solid wood options but they do not require painting or other finishes, nor will they warp or rot like wood does. However, WPCs are not maintenance-free and they can be degraded in outdoor environments. The wood in the WPCs can still be attacked by rot and mold fungi, and sunlight can discolor and break down the plastic component.

The wood in WPCs is normally used only as a low-cost, light-weight filler. As such, the inherent properties of the wood are not important. However, recent research at the UT Forest Products Center has shown that by using wood species with natural resistance to insects and fungi in WPCs, the durability of the composite can be improved. This result suggests that by taking advantage of the wood's properties, better WPCs are possible.

WPC is a relatively new product and comes in many formulations; thus its potential durability is not well understood. New WPC products in the future may provide even better performance.