Products from Mixed Plastic Lumber

Plastic lumber, as may be expected, has limited applications and use. It costs more than similar outdoor grade products/lumber and is therefore harder to sell, but offers superior resistance to degradation and weathering outdoors. There are transportation, industrial, marine and agricultural applications for plastic lumber products. Such products are generally not yet sold at a consumer level. A number of markets for plastic lumber products are tied to the activities of state and municipal agencies. The following marketplaces are estimated to have the most potential  

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Some of the procedures of value for processing of mixed plastic wastes may also be useful for the recovery of value from the laminates used for efficient packaging of food and beverages (e.g., milk cartons, Tetrapaks). A combination of heat and pressure may be employed on a recycle stream of this type of material to fuse the mixed fibrous and resin components into a dense board-like product [31, 32]. This highly weather and insect resistant product, Eco Superwood Plastic Lumber, may be sawn, nailed, drilled, etc., like wood, and it resists rotting in direct contact with the soil without the need for preservatives. 

Both blow molding and injection molding are downstream extensions of the extruder and are discussed separately. Profile extrusion is the direct manufacture of a product from the extruder die. The products are a continuous length with a constant cross section. Examples of profile extrusions include plastic pipe, garden hose and PVC window framing. Profile extrusion is the method now being used to create plastic lumber from mixed plastics. Extruders can also be arranged as coextruders where different layers... 

Plastics make up only about 8 percent of the volume in the average landfill but represent a huge investment of energy and raw materials. Most plastics produced from petroleum materials by polymerization of monomers such as ethylene or vinyl chloride are thermoplastic materials and can be cleaned, melted, and re-formed. Thermosetting plastics can also be cut into pieces that are mixed with other plastics or used as fillers. High-density polyethylene (HDPE) and polyethylene terephthalate (PETE) are the most widely reused plastic materials, but polyvinyl chloride (PVC), polypropylene, and polystyrene account for 5 percent of the recycled plastics. In 2001 80 million pounds (36 milfion kilograms) of plastics were recycled in the United States. Recycled plastic materials are used in the production of bottles, fabrics, flowerpots, furniture, plastic lumber, injection molded crates, and automobile parts. 

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. 

When mixed plastics streams are collected, separation by resin type may not be feasible or economical. Similarly, heavily contaminated plastics streams may not be suitable for high-value end markets. Use of plastics in a commingled form, typically in applications where plastics replace wood or concrete, offers relatively low-value end uses that are much more tolerant of contamination than traditional plastic resin markets. In addition, the plastic substitutes for lumber and concrete tend to be considerably more durable than the materials they replace. This is especially true for plastic lumber, where the plastics also have the benefit of not employing some of the toxic chemical systems used to protect wood from degradation in moist outdoor environments. Many companies have been into and out of the commingled plastics business. The products typically sell for more than the wood or concrete items they replace, and convincing people to buy the products, even when they will last considerably longer than the cheaper alternatives, has been difficult. 

Polymeri.x/ Trimax Plastic Lumber 4 Frasetto Way 85% post-consumer Lincoln Park, 15%i post-commercial NJ 07035 (516) 471-7777 Accepts mixed plastic and/or HDPE, depending on production level and influx from existing accounts... 

The information in Part II is from Technologies for Recycling Post-Consumer Mixed Plastics—Plastic Lumber Production, Emer ng Separation Technologies, Waste Plastic Handlers and Equipment Manufacturers, prepared by Bruce A. Hegberg, Gary R. Brenniman, and William H. Hallenbeck of the University of Illinois Center for Solid Waste Management and Research for the Illinois Department of Energy and Natural Resources, Office of Solid Waste and Renewable Resources, March 1991. 

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