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

Abstract

Composite consisting of polypropylene reinforced with short sisal fibers were prepared by melt-mixing and solution-mixing methods. In the melt-mixing technique, mixing parameters were optimised by varying the mixing time, rotor speed and chamber temperature. A mixing time of 10 min, rotor speed of 50 rpm and a mixing temperature of 170°C were found to be the optimum mixing conditions. Tensile properties of melt-mixed and solution-mixed composites were compared. Under optimum mixing conditions melt-mixed composites 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 distribution curves and optical photomicrographs. The effect of chemical treatment on the tensile properties of sisal/PP composites was investigated. Treatments with chemicals such as sodium hydroxide, maleic anhydride, urethane derivative of PPG, and permanganate were carried out to improve the bonding at the fiber/polymer interface. It has been observed that all the treatments enhanced the tensile properties of the composites considerably, but to varying degrees.