Production of microcellular foamed PVC/wood-fibre composites: Processing and cell morphology relationship

A microcellular polymer is a foamed plastic characterized by a cell density in the range of 10(9) and 10(15) cells/cm(3) and a fully grown cell size in the range of 0.1 to 10 mu m. The plastic/wood-fibre composites utilize wood-fibres as a reinforcing filler in the polymer matrix and are known to be advantageous over the neat polymers in terms of the materials cost and some mechanical properties such as stiffness and strength. These wood-fibre composites are microcellular processed to create a new class of materials with unique properties. Recent studies have demonstrated the feasibility of developing microcellular structures in PVC/wood-fibre composites. In this research, the effects of the materials and the processing conditions on the cell morphology of foamed PVC/wood-fibre composites are studied with a view to establishing the process-structure relationships for these materials. Each step of microcellular PVC/wood-fibre composites processing is addressed including: the surface treatment of the wood-fibre; the mixing of polymer and wood-fibre; the manufacture of the composites; the saturation of the composites with gas; the microcellular foaming of the composites and the cell morphology characterization of foamed composites. The experimental results indicate that the cellular morphologies of the foamed PVC/wood-fibre composites are a strong function of the content of plasticizer and the surface treatment of wood-fibre as well as the gas saturation and foaming conditions.