1 WOOD AND FLAX FIBER POLYOLEFIN COMPOSITES J. Denault, M-T. Ton-That, F .Perrin-Sarazin, and K. C. Cole National Research Council Canada, Industrial Materials Institute 75 De Mortagne, Boucherville, Quebec, J4B 6Y4, Canada johanne.denault@cnrc-nrc.gc.ca Abstract In this work, natural fiber and wood composites based on neat and recycled polypropylene (PP) were fabricated by melt processing. Different formulations, including various reinforcement content, different types of coupling agents, different types of reactive additives, and an impact modifier were developed. The reinforcements were in the form of natural fibers like banana, flax, rice husk and palm fibers and of wood sawdust. For the long fiber composite systems, processing was done by compression molding of piles of long fiber mat and extruded polypropylene film. For the short fiber composite, the samples were prepared by extrusion followed by injection molding. The tensile, flexural and impact performance were characterized and all composites show superior mechanical properties when compared with the pristine matrix. Mechanical performance of the wood composites was also evaluated before and after conditioning in water for 1 and 7 days. Results indicate that the composites resist to humidity very well. The results also demonstrate the effect of formulations on the performance of the recycled composites. INTRODUCTION Although much of the pioneering work in wood-filled thermoplastic composites was done in the 1970s [1-3], only recently there has been substantial development. The market for thermoplastic wood composites in North America was 320,000 tonnes in 2000 and the volume is expected to more than double by 2005 [4]. Wood plastic composites are gaining market share because of their advantages over wood and metal in terms of longevity, appearance, life-cycle cost, and value. They are attractive, insect and rot resistant, and paintable while they can be made to have a wood look. In addition, they are stiffer than plastic products while at the same time they can be worked, cut, glued and fastened with the same screws, nails, or staples as wood. The great majority of reinforced thermoplastic composites available commercially use as their reinforcing fillers inorganic materials like glass, clays, minerals, etc. These materials are heavy and abrasive to processing equipment. In contrast with conventional reinforcements, wood and natural fibers possess the advantages of low cost, light weight and non-abrasiveness. In addition, compared to natural fibers, wood fibers are very cheap, therefore it is not surprising that wood fibers are more attractive for composite production [5-16]. At this stage in the technology, the processing of wood thermoplastic composites has been well explored. Wood thermoplastic composites can be processed either by co-rotating or counter-rotating or parallel or conical twin-screw extruders, or single-screw extruders as well. Wood thermoplastic composites can be compounded by an inline or offline procedure, using continuous or batch processes. However it is essential that the wood reinforcement must be