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.