wood plastic composite production
Jun 01 , 2021
Wood-plastic composites (WPCs) are produced by thoroughly mixing ground wood particles and heated thermoplastic resin. The most common method of production is to extrude the material into the desired shape, though injection molding is also used. WPCs may be produced from either virgin or recycled thermoplastics including HDPE, LDPE, PVC, PP, ABS, PS, and PLA. Polyethylene-based WPCs are by far the most common. Additives such as colorants, coupling agents, UV stabilizers, blowing agents, foaming agents, and lubricants help tailor the end product to the target area of application. Extruded WPCs are formed into both solid and hollow profiles. A large variety of injection molded parts are also produced, from automotive door panels to cell phone covers.
In some manufacturing facilities, the constituents are combined and processed in a pelletizing extruder, which produces pellets of the new material. The pellets are then re-melted and formed into the final shape. Other manufacturers complete the finished part in a single step of mixing and extrusion.
Due to the addition of organic material, WPCs are usually processed at far lower temperatures than traditional plastics during extrusion and injection molding. WPCs tend to process at temperatures of about 50 °F (28 °C) lower than the same, unfilled material, for instance. Most will begin to burn at temperatures around 400 °F (204 °C). Processing WPCs at excessively high temperatures increases the risk of shearing, or burning and discoloration resulting from pushing a material that’s too hot through a gate which is too small, during injection molding. The ratio of wood to plastic in the composite will ultimately determine the melt flow index (MFI) of the WPC, with larger amounts of wood generally leading to a lower MFI.
