Twin screw compounding of PE-HD wood flour composites

The compounding of wood flour filled polyethylene is discussed with referen ce to co-rotating twin-screw extruders from two manufacturers. An acrylic a cid-grafted polyethylene (PE-HD-AA) copolymer was used as the compatibilize r in high density polyethylene wood flour (PE-HD/WF) composite system. Spec ial consideration was given to the compounding of the heat- and shear sensi tive wood flour The relevant screw configuration was found to consist of sh ort mixing length with low intensity of shearing. A suitable combination of processing variables was necessary for limiting the thermal degradation of the wood filler however tensile properties of the composites were not affe cted much. Furthermore, the allowable range of processing temperature was l imited, and there was an zipper bound of rotating speed and a lower bound o f throughput rate within which the darkening of wood filler in the composit es was acceptable. Vie processing window was also experimentally constructe d in terms of the degree of darkening of wood composites.