Effect of maleated polypropylene as coupling agent for polypropylene composites reinforced with hemp strands

New composites based on poly(propylene) as polymer matrix and hemp strands as natural reinforcement have been developed by injection-molding. The materials were previously mixed in a two roll mill to induce the dispersion of the fiber inside the polymer. To improve the adhesion between both components, maleated poly(propylene) was added as coupling agent, at 4% wt/wt with respect to hemp strands. The addition of this amount of this coupling agent to the formulation modified with 40 wt % of hemp strands increases the ultimate tensile strength (sigma(t)) and flexural strength (sigma(t)) up to 49 and 38%, respectively, compared with the composite without coupling agent. The interaction between the surface of hemp strands and the coupling agent was determined by FT-IR spectroscopy assuming that a covalent bond was established, avoiding the adverse effect of the poor compatibility at the interface for this kind of composites. (c) 2006 Wiley Periodicals, Inc.