Thermoplastic matrices for the use in WPCs need to be processable at
temperatures below 200 °C, since wood constituents start to thermally
degrade at approximately 150 °C, and around 200 °C the degradation may
be substantial for many wood species (Fengel and Wegener 1983).
Thermal degradation is also dependent on the wood-plastic residence time
at higher temperatures, i.e. if the processing cycle is kept short it is possible
to use a higher peak temperature. Thermoplastic matrices currently used in
commercial WPCs are normally high density polyethylene (HDPE),
polypropylene (PP) or polyvinyl chloride (PVC). Other matrices that have
gained increased interest in recent years are so-called bioderived plastics,
e.g. cellulose esters and polylactates, which are made partly or fully from
renewable resources.