Extruded wood polymer composite and method of manufacture

A process for manufacturing a composite extruded structural product having a desired profile from recycled polyethylene and wood fiber comprising the steps of:

• finely dividing recycled polyethylene and wood fiber each into particles of a size between 10 mesh and 40 mesh;
• mechanically mixing together the polyethylene particles and the wood fiber particles in a ratio of between 60%-40% and 40%-60% by weight, and an effective amount of a powdered endothermic foaming agent, to form a feedstock mixture;
• introducing the feedstock mixture, without pre-pelletization, into a heated screw-type extruder discharging into a molding die, said molding die having an entrance, a throat, and an exit having the shape of a desired product;
• mechanically mixing, compressing and heating said feedstock mixture in said extruder until it becomes plastic and homogenous;
• extracting excess volatiles and foaming agent process gas under vacuum from said feedstock mixture prior to entering said molding die;
• forcing said heated, plastic, homogenous mixture through said molding die to produce an extruded product having a surface which is relatively dense, tight-grained and strong, and a center which is relatively more porous and less dense;
• cooling said extruded product upon emerging from said molding die;
• and
• cutting the cooled extruded product into desired lengths.