Study on mechanical properties and thermal stability of polypropylene/hemp fiber composites

Polypropylene and hemp fiber composites were prepared by melt compounding, followed by injection molding. Maleic anhydride grafted polypropylene (PP-MAH), maleic anhydride grafted styrene-(ethylene-co-butylene)-styrene copolymer (SEBS-MAH) and maleic anhydride grafted Poly(ethylene octane) (POE-MAH) were used as compatilizer to improve the fiber/matrix interactions. The composites were characterized by X-ray diffraction (XRD), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), mechanical testing and thermogravimetric analysis (TGA). The mechanical properties of polypropylene/hemp fiber composites (fiber loading 30 wt%) at different compatilizer content were analyzed. In comparison to unmodified system, the incorporation of compatilizer (PP-MAH, SEBS-MAH, POE-MAH) can significantly enhance the fiber/matrix adhesion which resulted in higher stiffness and mechanical properties of the composites. The combination of PP-MAH and SEBS-MAH (or POE-MAH) elastomer can be used to optimize the mechanical properties of the composites. The tensile strength, flexural strength, notched and unnotched impact strengths of the composite comprising PP-MAH (5 phr) and POE-MAH (6 phr) were 22%, 8%, 24%, and 82% higher, respectively, than that of unmodified system. Furthermore, the addition of hemp fiber shifted the start of the degradation process and the maximum decomposition temperatures of the components to higher temperatures.