Wood – thermoset composites date to the early 1900’s. An earlier commercial composite material marketed under the trade name ” Bakelite”, was made of phenol – formaldehyde & wood flour. Its first commercial use was reportedly as a gearshift knob for Rolls Royce in 1916.This paper is focused on wood – thermoplastics, which in today’s parlance are simply referred to as Composite wood plastic.
The birth of the Composite wood plastic industry involved the interfacing of two industries that have historically known little about each other & have different knowledge, expertise & perspectives. The plastics industry has knowledge of plastics processing & the forest products industry has more experience & resources in the building products market. Not surprisingly, some of the earliest companies to produce Composite wood plastic’s were window manufacturers who had experience with both wood & plastics.
The plastics industry has traditionally used talc, calcium carbonate, mica, and glass fiber to modify the performance of plastics. About 2.5 billion Kgs of fillers & reinforcements are used annually. The industry was reluctant to use wood or other natural fibers such as kenaf, flax & hemp, though these fibers are from a renewable resource, are less expensive, lighter & less abrasive on processing equipments than conventional fillers. Most plastic processors ignored wood fiber because of its low bulk density & specific gravity, low thermal stability & tendency to absorb moisture.
The majority of thermoplastics have a bulk density of approximately 0.5 gms/cc. The plastics processor had to face the problem of how to consistently meter & force low bulk density wood flour into small openings typical of plastic processing equipments. In addition, the processing temperature for even the low softening plastics is often too high for incorporation of wood filler without thermal degradation. The high moisture content of wood & other natural fibers is also often problematic to the plastic industry which considers 1 to 2 % moisture content high. Even plastics processors having vented equipments capable of removing moisture during processing were averse to removing 5 to 7 % moisture from wood fiber. Resin dryers, which are fitted on plastic processing equipments, are not sufficient for wood filler or particles. Drying of wood or other natural fibbers poses a fire hazard. Plastics processors who tried to use wood or other natural fibers often lacked the knowledge of cellulosic materials & their failed attempts made the industry generally skeptical of combining wood & plastic Composite wood decking.
For the wood products industry, thermoplastics were a foreign world, although they attempted products such as Vinyl sidings. Competing in different markets, forest & plastics industries had few material & equipment suppliers in common& they processed materials very differently & on entirely different scales Wood Plastic Composite Floor.