Addition of Hybrid Coupling Agent Based Natural Rubber-Starch on Natural Rubber Composite

Natural rubber blended with biomass fibers as a filler is one of promising methods to produce high-quality car tire that require good thermal resistance and low noise level caused by the frictional forces between the tire and road. Biomass fibers have suitable acoustic properties, good tensile strength, and also density regarding its chain molecule structure and porous structure. The major biomass byproduct from the palm oil industry in Indonesia is empty fruit bunches (EFBs). Because of the different polarity of natural rubber and EFBs, coupling agent has to be added for producing composite with good miscibility and desired mechanical properties. In this study the hybrid coupling agent based natural rubber-starch prepared with glow discharge electrolysis plasma method is added to the natural rubber/EFBs fibers composite. The ratio of EFBs fibers to the composite is varied to 5, 10, and 15 phr, while the coupling agent is added at fixed 1 phr. Field emission scanning electron microscopy (SEM) and mechanical testing are used for the composite characterization. The mechanical tests showed that the addition of coupling agents provides greater tensile strength compared to composites without the addition of coupling agent. These results are supported by morphology analyses using SEM, showing the good interaction on the surface between the EFBs fibers and the natural rubber matrix with addition of the coupling agent.