MECHANICAL-PROPERTIES OF WOOD-FIBER TOUGHENED ISOTACTIC POLYPROPYLENECOMPOSITES/

This study investigates the mechanical properties of wood-fiber/toughe ned PP composite modified by physical blending with an EPDM rubber to improve impact toughness. Wood-fiber thermoplastic composites were pre pared with a modified PP matrix resin, employing high shear thermokine tic compounding aided with maleated PP for the fiber dispersion. The a ddition of EPDM improved the impact toughness, while it reduced stiffn ess and strength properties. To compensate the non-plane strain fractu re toughness, the specimen strength ratio (R(sb)) was adopted as a com parative measure of fracture toughness. The strength ratio increased w ith the addition of EPDM, while it decreased with increasing wood-fibe r concentration. The work of fracture increased with EPDM level except at large wood-fiber concentration. The effectiveness of the impact mo dification was assessed with the balance between tensile modulus and u nnotched impact energy as a function of wood-fiber concentration. EPDM rubber modification was moderately effective for wood-fiber PP compos ites. The examination of fracture surfaces showed twisted fibers, fibe r breakage, and fiber pull-out from the matrix resin.