Morphology, thermal and mechanical properties of extruded injection molded kenaf fiber reinforced polypropylene composites

The aim of this study is to explore the effect of coupling agent and surface treatment of natural fibers on the correlations among structural, thermal and mechanical behavior of injection molded composites. Polypropylene (PP)-based composites reinforced with kenaf fiber as a biodegradable filler were fabricated. Kenaf composites were prepared by adding 10, 20, 30, and 40 wt% of kenaf fibers into the matrix using melt mixing and injection molding considered as a simple, scalable, conventional, and efficient process, that is. Different concentrations of NaOH were applied to modify kenaf fibers. The scanning electron microscope (SEM), Fourier Transform Infrared (FTIR), and x-ray Diffraction (XRD) analysis were conducted in order to find the optimum concentration of NaOH for the chemical treatment and to study the morphology of the fabricated specimens. Maleic anhydride polypropylene (MAPP) was employed as the coupling agent. Moreover, the tensile, flexural and impact tests were conducted to evaluate the mechanical properties of the specimens. Results showed that by the incorporation of kenaf fibers of up to 40 wt%, the tensile and flexural strength significantly improved by 100% and 120%, respectively, with respect to those exhibited by the neat PP. It was shown however that the impact strength decreased by around 18%. Moreover, the results of thermal analysis using the differential scanning calorimetry (DSC) showed that the addition of kenaf fibers into the PP matrix increases the melting and crystallization temperature, and the degree of crystallinity. The XRD analysis of composites further confirmed the influence of fibers on the PP crystallization behavior. The results of this work can further extend the use of natural fiber-reinforced PP composites for structural applications such as automotive interior parts. (paper)