Effect of epoxidation levels on curing characteristic and mechanical properties of ENR/MFC composites

Abstract

This study aimed to investigate the effect of epoxidation levels on the curing and tensile properties of epoxidized natural rubber (ENR)/microfibrillated cellulose (MFC) composites. ENRs with different levels of epoxidation were first prepared from natural rubber (NR) latex via ‘in situ’ performic epoxidation using 0.75 M formic acid and 1 M hydrogen peroxide at 50°C at various reaction times. The results from H1 NMR revealed that the reaction at 2, 4, and 6 hours could achieve 20, 30, and 40 mol % epoxidation, respectively. The introduction of epoxide groups into NR chains reduced the scorch and cure time along with the increase of the epoxy content. Furthermore, it was observed that the tensile strength rose remarkably at 30 mol% epoxidation (ENR30). Therefore, the ENR30 was subsequently chosen to prepare the composites with various amounts of MFC (1, 3, and 5 parts per hundred rubber, phr). Interestingly, incorporating MFC elevated tensile strength and elongation at break of ENR30. At 5 phr of MFC, the composite possessed the highest tensile strength and elongation at break value, which reached up to 31.07 MPa and 922.92%, respectively.