Recycled plastic lumber properties

Mixed recycled plastic lumber bridge decks, boat docks, doors, floors, furniture, windows, fences, pallets, etc. are product examples in service. Plastic lumber would be maintenance-free for at least half a century, as opposed to 15 years for treated wood and 5 yeare for untreated wood. Extensive use is made in applying plastics in wood to improve their structural and decorative properties. 

In 1999, the Plastic Lumber Trade Association reported that recycled plastic lumber (RPL) was growing at a 30 percent annual rate. Growth of plastic lumber has been fueled by growing knowledge about performance properties of the material and how they relate to composition, as well as by the development of performance standards such as the standard test methods developed by ASTM. By the end of 2000, eight ASTM test methods for RPL had been established, and several others were at various stages of the development process. The Association has also participated in a number of demonstration projects. ... 

Wood fiber - recycled plastic composite lumber is a relatively new development and is similar to PS addition to plastic lumber because the potential exists for improved mechanical properties and dimensional stabilities. Wood fiber addition can serve as an excellent reinforcement for plastics, and wood fibers are abundant, lightweight, nonabrasive, nonhazardous and inexpensive. An effort is being made to examine the incorporation of treated and untreated aspen fibers into recycled HDPE milk bottles [Yam et al., 1990]. The work has shown tensile strength and Izod impact strength below that of HDPE alone when aspen fiber is added. Tensile modulus and flexural modulus are increased significantly above HDPE alone with the addition of wood fiber. Dispersion of the fiber in the resin has been reported as a dominating factor in the process thus far. 

Post-consumer waste consists of six major polymers polystyrene (PS), low density polyethylene (LDPE), high density polyethylene (HOPE), polypropylene (PP), polyvinyl chloride (PVC) and polyethylene terephthalate (PET). These polymers are incompatible and form separate phases on mixing. Fabricated products made directly from comingled plastics have poor physical properties, and can compete only with treated lumber at a price of roughly 20% of that for the virgin plastics. When freed of hidden and actual subsidies, this form of recycling is believed to have a negative economic value. 

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