Effects of different supercritical temperatures on the modification of aramid pulp surface via coating silica to enhance the properties of EPDM composites

Abstract Poor dispersion is a major disadvantage of aramid pulp (AP) reinforced composites. In this study, nano‐silica (SiO₂), as the surface modifier and reinforcing agent, was synthesized on AP surfaces to improve the dispersed character in ethylene‐propylene‐diene elastomer (EPDM) using supercritical carbon dioxide (scCO₂). The influence of the temperature of scCO₂ on treated AP, configuration of the surface, and mechanical performance of AP/EPDM composites were studied. Based on the results of Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy, SiO₂ was chemically grafted onto the AP surface. The SiO₂ nanoparticles were uniformly deposited on the AP surface, and the roughness of AP was increased based on the SEM results. The optimum temperature of the supercritical reaction was 100°C considering the results of all the tests. Under the optimum temperature and with 10 phr of AP, the mechanical properties, oil resistance, and dynamic mechanical properties of the SiO₂‐AP/EPDM composites were investigated. The tensile strength and tear strength of the SiO₂‐AP/EPDM were improved by 121.1 and 134.9%, respectively, compared with that of the pure AP/EPDM composites. The fracture surface of the SiO₂‐AP/EPDM composites showed that SiO₂‐modified AP had a good dispersion in EPDM, and AP and EPDM had good interfacial bonding. Dynamic mechanical analysis results showed that the storage modulus of the composites was improved greatly compared with the pure AP/EPDM, and the loss factor also increased. The oil resistance of the composites was also improved.