The effect of bleaching treatment on the mechanical strength of PP-Kenaf composite

Polypropylene (PP) is a versatile thermoplastic polymer that has various applications. Since it has relatively low mechanical strength the application of PP is limited to packaging or any application that does not involve high impact during its lifetime. Increasing the mechanical strength of PP requires blending this polymer with reinforcing material such as Kenaf fiber. However these two materials are not compatible enough to produce composite with desired mechanical properties. The aim of this work was to study the effect of chemical treatment on Kenaf fiber to the mechanical strength of PP-Kenaf composite. The applied chemical treatment to Kenaf fiber was bleaching process using 1% v/v NaClO solution for 2 hours at room temperature. Kenaf fibers, treated and untreated, were characterized using Fourier Transform Infrared (FTIR), Field Emission Scanning Electron Microscope (FESEM), and Universal Testing Machine (UTM). The chemically treated fibers were then blended with PP using hot melt mixing method at various fiber loadings i.e. 5, 15, and 25%. The variations for mixing temperature and duration were 170-190°C and 10-20 minutes. The morphology, thermal stability, and mechanical strength of the resulting composites were characterized using FESEM, Simultaneous Thermal Analysis (STA), and UTM. This study showed that the composite with highest tensile strength and thermal stability was PP-Kenaf composite at 5% fiber loading where the mixing process of PP and Kenaf fiber was performed at 190°C for 20 minutes. Higher loading of fiber lowered the amount PP matrix that supports the fiber thus decreasing the tensile strength of the composite.