Wood Plastic Composite

Wood plastic composite (WPC composite, or composite lumbar) is a hybrid material composed of natural wood and plastic fiber. Sawdust from fiber fillers like pulp, peanut hulls, and bamboo are mixed with new or waste plastic powder, from composite plastic materials such as polyethylene, polyvinyl chloride, polypropylene, and acrylonitrile butadiene styrene. Once the materials are mixed together to achieve a relatively thick consistency, they are extruded or molded.

See our guide to wood plastic composite suppliers.

Composite Lumber - Plastic and Wood

Additives, such as colorants, reinforcing agents, and lubricants can be added to achieve a higher level of specification for the intended product’s use. Because of the composite’s unique composition, wood plastic composite can be manipulated to assume a wide array of shapes and dimensions, including arched and bent shapes. As a result of their high cellulose content, wood plastic composites can be treated in a similar fashion as wood, but they are also moisture- and rot-resistant.

WPC Wood Plastic Applications

Wood plastic composite (WPC) that consists of polyethylene (PE) and wood sawdust tends to be used primarily in building and structural components. WPC comprised of wood sawdust and polypropylene (PP), on the other hand, is more commonly used for automotive and consumer products. Wood sawdust and polyvinyl chloride (PVC) create a WPC that is typically found in window manufacturing, as well as certain decking applications. The combination of acrylonitrile butadiene styrene (ABS) and wood sawdust produces a WPC that can also be used in varying applications.

Material selection depends in large part upon the manufacturer’s preference, and is based on the general properties of each component as well as availability. Wood components are generally used in sawdust form or small fibers, and typically comprise between 50 and 70 percent of the final wood plastic composite. Maple, oak, and pine are common types of sawdust, and tend to be relatively low-cost to obtain.

Because of the high cellulose content from the wood, WPC assumes many of the same characteristics of wood and can be subjected to the same processes, including planning, drilling, and sanding. Nails, screws, and other fasteners often achieve greater hold when used with WPC than with lumber, which results in WPC’s ability to use smaller fasteners to hold more. Additionally, WPC offers superior water resistance when compared to basic wood with minimal expansion. The lack of moisture present within WPC also results in resistance to decay. The ability of WPC to perform in high-temperature environments is also better than that of wood.

To achieve the varying characteristics listed above, the manner in which the wood is processed and interfacial adhesion must be controlled. The difference between the surface energy of the wood and the matrix of the plastic polymer determines the final physical properties of the composite, often requiring the addition of a coupling agent to enable strong interfacial adhesion. Coupling agents encourage dissimilar materials (such as plastic and wood) to form an alloy. Compatibilization can also be used, a process by which wetting is achieved within the mixture. There are several manners in which coupling and compatibilization can take place, including the modification of the fiber or polymer and the addition of coupling agents. Depending on the type of wood and plastic involved, different coupling agents and compatibilizers may be appropriate.

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