Abstract

Composites made from wood, other biomass resources and polymers have existed for a long time but the nature of many of these composites has changed in recent decades. Wood-thermoset composites date to the early 1900s. “Thermosets” or thermosetting polymers are plastics that, once cured, cannot be remelted by heating. These include cured resins such as epoxies and phenolics, plastics used as wood adhesives with which the forest products industry is traditionally most familiar (see Chapter 9). For example, an early commercial composite marketed under the trade name Bakelite was composed of phenol–formaldehyde and wood flour. Its first commercial use was reportedly as a gearshift knob for Rolls Royce in 1916 (Gordon 1988). “Thermoplastics” are plastics that can be repeatedly melted, such as polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC). Thermoplastics are used to make many diverse commercial products such as milk jugs, grocery bags, and siding for homes. In contrast to the wood–thermoset composites, wood–thermoplastic composites have seen large growth in recent decades. Wood–thermoplastic composites are now most often simply referred to as wood-plastic composites (WPCs) with the common understanding that plastic refers to a thermoplastic.