In this study, properties of natural rubber (NR) were enhanced by adding sisal fiber, which is a tropical plant in Thailand. Sisal fiber/natural rubber composites were prepared by the incorporation of sisal fiber at various loadings into natural rubber. Natural rubber grafted with maleic anhydride (NR-g-MA) prepared in house and epoxidized natural rubber (ENR50) were used to enhance the compatibility between sisal fiber and natural rubber. With increasing fiber loading, tear strength and hardness of natural rubber composites increased while their scorch time, cure time, tensile strength, and elongation at break decreased. Moreover, interfacial adhesion between sisal fiber and natural rubber was enhanced with the addition of NR-g-MA and ENR50. In comparison, NR-g-MA provided more effective improvement in mechanical properties of natural rubber composites than ENR50. For NR-g-MA compatibilized natural rubber composite at fiber loading of 10 phr, its tensile strength, modulus at 100% strain, modulus at 300% strain, tear strength, and hardness were increased 43, 44, 53, 42, and 13%, respectively, comparing with that of uncompatibilized natural rubber composite.
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