Abstract

Reinforcing polymers with cellulosic fibers is often an inexpensive route to increasing mechanical properties and reducing cost. The sources of cellulosic fibers are often waste by-products. These sources include wood flour, nut shells, and fibers from various plants (vegetables, kute, flax, hemp, pineapple, bamboo, etc.). The mechanical properties of these cellulose/polymer composites (i.e., strength, modulus, toughness) are almost always further improved if the fiber and/or polymer matrix are modified such that fiber/matrix adhesion is enhanced. Cellulose reinforced composites have recently found commercial applications in the automotive and agricultural industries. Here we report on the behavior of kudzu fiber-reinforced polypropylene. Kudzu is a noxious weed that grows in the southeastern United States. Previously in our laboratory we have optimized pulping procedures for kudzu fibers and produced kudzu paper with properties comparable to that of softwood kraft. In the current work, kudzu pulp has been melt blended with polypropylene (PP) and maleic anhydride-grafted polypropylene (MAPP). Modest increases (18%) in tensile strength were measured when 30 percent kudzu pulp was blended with PP. However, when 10 and 23 percent MAPP was also blended with PP and 30 percent kudzu pulp, tensile strengths increased by 29 and 52 percent, respectively, compared with unfilled PP. Significant increases in tensile modulus were also found for 30 to 40 percent fiber loadings. The melt blending conditions (mixing time, melt temperature, and strain rate) also had an effect on the tensile properties for these com- posites. The effects of these conditions on the dispersion of the fibers in the PP matrix were characterized by optimal and scanning electron microscopy. These results are correlated with the mechanical properties. Also, the effect of MAPP content on the nature of the interaction between fiber and matrix was determined via Fourier transform infrared spectroscopy.