Microcellular wood fibre reinforced polypropylene composites in an injection moulding process

Microcellular foams of polypropylene containing wood fibres, cell sizes on the order of 10 to 50 M were produced by injection moulding. The relationships of processing/structure/property were investigated for wood fibre-thermoplastics composites foaming with a chemical blowing agent. Wood polypropylene composites (WPC) of different wood content (30%, 40%, 50% and 60% by weight) were prepared using maleic anhydride-polypropylene copolymer (5% relative to the wood fibre content) as a coupling agent. Measurement of density, cell size, void content, tensile and flexural test of the prepared WPC were carried out. The shape and distribution of the voids were investigated by optical photo examination of longitudinal sections of specimens, using a polishing technique and reflected light microscopy. The density of foamed composites decreased about 24%. The cell morphology and foam properties showed improvement when the coupling agent was added. Water absorption and scanning electron microscope of the composites also investigated.