Conventional single screw extruder is not suitable for WPC forming operation, because it processes the weak ability for material transmission and plasticization. The transmission affection of single screw extruder mainly depends on the role of friction. The wood structure is too fluffy to feed, and the filling of wood structure make the polymer melt viscosity increase which makes extruding more difficult, so that the material has a longer residence time in the cylinder, and at the same time it cannot operate to the plant fiber with high water percentage for its poor exhausting affection .Therefore, conventional single screw extruder will be greatly restricted in the extruding process of wood-plastic composite materials.

The single screw extruder, which can be applied to the WPC forming operation, should use the specially designed screw. This kind of screw should have strong ability for material transmission and mixing material plasticization, and it can often mix and pelletize materials before extruding.