Studies on composites from wood and polypropylenes. II

Abstract

Abstract Composites of polypropylene (PP) or maleic‐anhydride‐modified polypropylene (MPP) with refiner ground pulp (RGP) were prepared under various kneading conditions (mixing temperature, rate of rotation, and mixing time) and evaluated for their tensile strength (σ max ), break elongation (ϵ max ), and Young's modulus ( E ). Particularly, for the rate of rotation, fiber length distribution and its fibrillation were investigated in connection with mechanical properties of the composites. Also evaluated in this study was the effect of modifiers of PP on the properties. Modified PP that can be grafted or can have affinity to RGP was proved to improve the tensile strength of the molded composites as the RGP content increases, while the strength was decreased for PP–RGP composite without a modifier. MPP was also evaluated as a compatibilizer for the PP–RGP composites, and a tremendous improvement of tensile strength was achieved with MPP addition of only 2.5%, indicating that MPP can act as a compatibilizer in its system. These lines of evidence is interpreted to be caused from the improvement of the adhesion between RGP and PP through localizing MPP at the interface of these two components.