Coating plywood with a thermoplastic

This work presents a method for the surfacing of wood sheets such as plywood with melt processable thermoplastic using extrusion coating. The method uses a direct coating of the plywood with a very hot low-viscosity coating. During the coating, the pressure of the melt is kept as low as possible. These factors produce a very high mechanical adhesion between the coating and the wood. In addition, the coating method uses a tool for preventing the formation of holes in the surface by the penetration of air expanding and water evaporating from the wood pores through the coating. In this work the method was applied to coating plywood with a copolymer of polypropylene. The adhesion between the wood and the polypropylene was improved by blending the polypropylene with maleated polypropylene wax. The experiments showed that the method produces sound and smooth polypropylene coated plywood. Addition of a modifying agent improves the adhesion between the polypropylene and the wood.