Composite materials wood/plastic

It may also be possible to eventually extend this bonding concept to the preparation of flakeboards and other wood-base composite materials. If plastics like polystyrene are incorporated into the composite matrix, and successful bonding between the wood and plastic is developed through the graft polymers, the three-dimensional network of plastic material throughout the composite matrix may lead to enhanced physical and mechanical properties as well as improvements in dimensional stability (Figure 2). 

This research project represents initial studies into a new approach to blending thermoplastic materials like polystyrene with wood materials, leading to a new class of wood-plastic composites. Traditional wood-plastic composites have involved the impregnation and subsequent in situ polymerization of vinyl monomers. This procedure has been adopted for selected products for which improved physical properties justify increased production costs. While producing mixtures or blends of wood and plastics, these types of composites do not demonstrate significant chemical bonding between the wood and plastic components. 

J.D. Umpleby. Material choice for wood-plastic composites. In Wood-Plastic Composites—A Sustainable Future. International Conference, Vienna, Austria, May 14-16,... 

The term wood-plastic composites (WPG) covers an extremely wide range of composite materials using plastics ranging from polypropylene (PP) to polyvinyl chloride (PVC) and binders/fillers ranging from wood flour to flax. These new materials extend the current concept of wood composites from the traditional compressed materials such as... 

Laminates aie materials made up of plies or laminae stacked up like a deck of cards and bonded together. Plywood is a common example of a laminate. It is made up of thin pHes of wood veneer bonded together with various glues. Laminates ate a form of composite material, ie, they ate constmcted from a continuous matrix and a reinforcing material (1) (see also Reinforced plastics). 

Wood-plastic composites (WPC) are used as building material for decking, fencing, siding. .. for the low maintenance constraints. US demand is forecast at 2.5 billion through 2008. 

In addition, ABS that has been recovered can be recycled into high value composites without separation from impurities. This has been exemplified with wood-plastic composites that contain ABS as matrix polymer. Both virgin ABS and recycled ABS were used and the properties of the materials were compared (126). In order to increase the performance, coupling agents were used, all based on grafted maleic anhydride. 

With the advent of the polymer or plastic age, scientists had yet another group of chemicals to coat and treat the ancient raw material, wood. During World War II, phenol-formaldehyde, based on the research of the Forest Products Laboratory, was used to treat wood veneer and to form the composite into airplane propellers. Today, this same "Compreg" is used for cutlery handles throughout the world. 

The exact number is not known, but many high school industrial arts departments have installed the catalyst-heat system for making wood-plastics. The students produce the composite material and then fabricate it into various items during their shop classes. 

In 75% of the cases, wood fibres are the preferred filler for thermoplastic matrices. Their high availability may account for this. The resulting composite material is internationally known as WPC, which stands for wood plastic composite. They have been produced industrially since 1980 and the market has gradually increased in the last 10 years, especially in the United States, reaching 700 000 metric tons with an 11% increase rate per annum. In Europe, the WPC market is considered to be emerging. At the best estimations, it reached only 100 000 metric tons in 2005 (Anonymous, 2006) and in lapan the market is even smaller. In America, more than 50% of the WPC is used for parquets and decking made with polyethylene. In Europe, it is the automobile sector that is preponderant with polypropylene-based composites. 

Bonding of hydrophobic plastic materials to wood to create new wood-plastic (polystyrene) materials with improved mechanical and physical properties that incorporate the desirable features of each constituent is difficult to achieve. This is due to poor interfacial adhesion between the wood and polystyrene components because of their inherent incompatibility. New, well-defined, tailored cellulose-polystyrene graft copolymers have recently been prepared using anionic polymerization techniques. Preliminary bonding studies showed that these graft copolymers can function effectively as compatibi-lizers or interfacial agents to bond hydrophobic plastic (polystyrene) material to wood, evolving into a new class of composites. 

Let us take a look at a generic wood-plastic composite (WPC) deck, preferably of a premium quality. What should be done in order to avoid the deck owner complaints and, god forbid, a lawsuit Which properties of the deck should we consider, in order to extend its lifetime as much as possible, preferably longer than that of a common pressure-treated lumber deck In other words, what is required to make a material that is both durable enough to meet the warranty guidelines and at the same time cost-efflcitive to be competitive in the marketplace What can happen to the WPC deck in use, and how to prevent it Which properties of the composite material should we aim at, what should we study in that regard, what shonld we test and how, what shonld we optimize in order to make a premium product, or, at least—for a less ambitious manufacturer—to pass the building code ... 

Wood-plastic composite (WPC) deck boards are extruded or molded products of a specified shape and, by definition, represent plastic filled with cellulose fiber and other ingredients. In this context wood is a proxy for fibrous materials of plant origin. These materials will be considered in the next chapter. This chapter deals with a plastic component of composite deck boards, with an understanding that the plastic is thermoplastic. 

Polyethylene resins, employed in wood-plastic composite materials, typically belong to HDPE, and only in one case (Trex deck boards) it was LDPE (or LDPE/HDPE), originated from grocery sacks and stretch film, used as reclaimed plastic source. 

The term wood-plastic composites (WPCs) refers to wood as a proxy for fibrous materials of plant origin. It can be wood flour or sawdust, or agricultural plant residues, typically cut, milled, or ground, or other types of natural fiber, such as hemp, jute, and kenaf, commonly as a by-product of the respective industrial process. 

U.S. Pat. No. 3,875,088 [29] describes a composite material comprising 50-75% of a thermoplastic resin binder (ABS or rubber-modified polystyrene) and 20-40% of wood flonr (40 mesh and 100 mesh), with the ratio of plastic to wood flonr being between 1.5 and 3.0. 

U.S. Pat. No. 6,939,496 [43] discloses a system and method of extruding plastic-cellulose fiber composite material, comprising 60-95% by weight of a thermoplastic polymer such as polypropylene, polyethylene, and PVC, 20-30% of cellulose fiber obtained from such materials as wood sawdust (60 mesh particle size), hemp, flax, straw and wheat, and a binding agent mixed with the filler. 

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