Fabrication of highly filled wood plastic composite pallets with extrusion-compression molding technique

摘要

The aim of this study was to fabricate highly filled wood plastic composite pallets with extrusion-compression molding technique and investigate the effects of processing parameters on mechanical performance and production stability. The composites were blended in twin-screw extruder and subsequently measured by weight with an electronic scale. Before compression, it was divided into pieces and rearranged in the cavities of compression mould according to the mass distribution. The effects of compression pressure and mould temperature on flexure strength, density, water absorption, and dimensional deviation were investigated. The results show that both the flexure strength and density of the pallets increased with compression pressure and remained higher than that of extruded deck when compression pressure exceeded 6.5 MPa. Water absorption and dimensional deviation decreased with compression pressure and remained lower than that of extruded deck after the compression pressure exceeded 6.0 MPa. Compression pressure could increase the final passed yield by improving the composite melt filling state and lowering the buckling deformation, but further increase above 6.7 MPa would result in a decline in final passed yield. Increase in mould temperature contributed to the production stability but an excessive value would extend the molding cycle. The insights gained from this study may be of assistance in optimizing extrusion-compression processing parameters and expanding the application of highly filled wood plastic composites in complicated and irregular products.