Influence of wood fiber size on extrusion foaming of wood fiber/HDPE composites

Foaming of wood fiber/plastic composites (WPC) with a fine-celled structure can offer benefits such as improved ductility and impact strength, lowered material cost, and lowered weight, which can enhance their utility in many applications. Although a great deal of attention is now being focused on these composites in the scientific literature, there are still numerous aspects of WPC processing that need elucidation. In this context, this article investigates the effects of wood fiber (WF) size on fine-celled extrusion foaming of WPC in terms of cell size, cell size distribution, and foam density. The effects of WF size and coupling agent content on the viscosity of WPC are also investigated. The experimental results revealed that the small-sized WF provides a better cell morphology, a smaller cell size, and a better cell uniformity in WPC foams. (c) 2007 Wiley Periodicals, Inc.