Sisal Fiber/Natural Rubber Composites: Effect of Fiber Content and Interfacial Modification

Sisal fiber/natural rubber (NR) composites were prepared by the incorporation of sisal fiber into NR at contents of 10-30 phr. Fiber treatment (alkalization) and adding maleic anhydride grafted natural rubber (NR-g-MA) were used to improve interfacial adhesion between sisal fiber and NR matrix. Mechanical properties, morphologies, and cure characteristics of the composites were studied. With increasing fiber content, modulus at 100% strain (M100), modulus at 300% strain (M300), and hardness of the composites increased whereas tensile strength and elongation at break decreased. Cure time of the composites decreased with increasing fiber content but scorch time was not much affected by fiber content. Alkali treated sisal fiber/NR composite exhibited higher tensile properties and hardness than untreated sisal fiber/NR composite at all fiber content due to the improved adhesion between fiber and NR matrix through the mechanical interlocking mechanism. Alkalization showed no effect on scorch time and cure time of the composites. The addition of NR-g-MA into the composites increased M100, M300, tensile strength, and hardness but prolonged scorch time and cure time. NR-g-MA provided more effective improvement of the mechanical properties of the composites when compared to fiber alkalization.