Feasibility of Using Heat Treated Wood in Wood/Thermoplastic Composites

Using wood and other natural fibers with thermoplastic materials is always associated with a problem: poor compatibility between wood fibers and thermoplastic matrix. This paper deals with the mentioned problem and tries to solve, or at least ease, it through pre-heat treatment of wood prior to blending of wood fibers with other components of composites. In this study, wood pre-heat treated at different temperatures (175, 190 and 205 degrees C) was used at various loadings (25 and 50%) with high density polyethylene (HDPE) and polypropylene-maleic anhydride copolymer (MAPP) to produce composites. The composite properties, including mechanical performance and morphological character, were investigated. The results of this study show that pre-heat treatment temperature and coupling agent content did not impact the composite properties at 25% wood content. Adding treated wood at 50% level to the composites enhanced the mechanical properties in comparison with untreated wood. The degree of the enhancement depended on pre-heat treatment temperature. Using wood treated at 190 degrees C resulted in composites with the highest modulus of rupture (MOR) and tensile strength. In terms of modulus of elasticity (MOE), composites having wood treated at 205 degrees C showed the highest MOE in both tensile and flexural tests. Adding 2% coupling agent caused an improvement in modulus of rupture (MOR) and tensile strength. An increase in wood content from 25 to 50% deceased strain at maximum load drastically. Morphological study showed that the mode of fracture is a function of wood and coupling agent content, and pre-heat treatment temperature.