The manufacture of wood filled polymer materials has been an industrial process for about 80 years. Most of the early industrial applications of wood filled polymers occurred in thermosetting resin systems such as phenol-formaldehyde resins. Industrial applications of lignocellulosic filled thermoplastics were reported in the late 1960s. One of the largest segments of the wood filled thermoplastic industry centers on the production of wood plastic composite (wpc) decking material as a replacement for preservative treated wood and the more expensive durable wood species such as redwood and teak. Some of the positive attributes of wood filled plastic composite lumber compared to wood include it’s durability, low maintenance, no painting, insect and decay resistance, and it will not warp, splinter, crack, is denser and thus holds screws better and can be manufactured to be resistant to ultraviolet light.

Various extrusion processes are used to manufacture wood plastic lumber and some manufacturers, to reduce weight and material costs have adopted the manufacture of hollow cross-section profiles. The materials used to produce wood plastic composite lumber include thermoplastic resins, most notably, low and high density polyethylene, polypropylene and polyvinyl chloride. The polymers utilized typically need to have melting temperature that is below the thermal decomposition of wood (~225 degrees C). These thermoplastics can come from both virgin and recycled sources. The wood used to manufacture these composites is mostly in the form of wood flour (typically 40 mesh or lower) or recycled paper fiber. Wood contents typically range from 20 to 60% in these composites. Additives to the composites will include processing aids (lubricants, antioxidants, acid scavengers), and property enhancers (biocides, coupling agents, inorganic fillers, fire retardants, uv stabilzers, colorants, etc).

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