Effect of processing variables on the mechanical properties of sisal-fiber-reinforced polypropylene composites

Composite consisting of polypropylene reinforced with short sisal fibers we re prepared by melt-mixing and solution-mixing methods. In the melt-mixing technique. mixing parameters were optimised by varying the mixing time, rot or speed and chamber temperature. A mixing time of 10 min, rotor speed of 5 0 rpm and a mixing temperature of 170 degrees C were found to be the optimu m mixing conditions. Tensile properties of melt-mixed and solution-mixed co mposites were compared. Under optimum mixing conditions melt-mixed composit es showed better tensile properties than those of solution-mixed composites . The influence of fiber length, fiber loading and fiber orientation on the mechanical properties of PP/sisal composites has been evaluated. The fiber breakage and damage during melt-mixing were analysed from fiber-length dis tribution curves and optical photomicrographs. The effect of chemical treat ment on the tensile properties of sisal/PP composites was investigated. Tre atments with chemicals such as sodium hydroxide, maleic anhydride, urethane derivative of PPG, and permanganate were carried out to improve the bondin g at the fiber/polymer interface. It hits been observed that all the treatm ents enhanced the tensile properties of the composites considerably, but to varying degrees. (C) 1999 Elsevier Science Ltd. All rights reserved.