WOOD FIBER REINFORCED COMPOSITES

The reinforcement of polypropylene (PP) using wood cellulose has been studied. The strength and stiffness of the composites are improved by a prehydrolytic treatment of the cellulose as well as by the use of maleic anhydride-modified PP (MAPP) as a coupling agent for promoting interfacial adhesion. The embrittlement of the cellulosic component brought about by the hydrolysis facilitates fine dispersion of fibers in the shear field of the compounding extruder. The E-modulus of composites based on prehydrolyzed fibers is significantly improved as compared with untreated fibers and exceeds values calculated theoretically with the Halpin-Tsai equation. Strength values increase with increased fiber content, which is a remarkable characteristic for such composites. Significant improvement of the modulus and strength in composites with hydrolyzed fibers indicates that such fibers are disintegrated into microfibrils characterized by very high modulus and strength values. Selecting suitable processing conditions was found to be crucial for the chemical reaction between the MAPP coupling agent and fiber surface, which produces improved adhesion.