Enhancing the thermal and mechanical properties of carbon fiber/natural rubber composites by co-modification of dopamine and silane coupling agents

In order to manufacture high-speed rubber tracks, it is urgent to develop natural rubber composites with excellent thermal and mechanical properties. In this paper, natural rubber was filled with milled carbon fiber (CF) which was synergistically modified by dopamine and silane coupling agent (SCA), including KH560, KH570 and KH590. Firstly, the polydopamine initial platform was formed on CF surface through self-polymerization of dopamine. Subsequently, SCA was grafted to improve the interface properties between the filler and the matrix. Eventually, the co-modified CF filled natural rubber (CF/NR) was fabricated by mechanical mixing method. The modification process was confirmed by scanning electron microscopy and other characterization methods. The heat build-up, thermal conductivity and mechanical properties of CF/NR were compared. The results showed that SCA could effectively graft on the polydopamine platform, and the thermal and mechanical properties of the three silane functionalized carbon fiber filled natural rubber composites were improved in different degrees. Among them, the carbon fiber grafted with KH590 filled natural rubber had the best comprehensive properties. Concretely, the thermal conductivity increased by 71.3% compared with the unfilled natural rubber, and the tensile strength increased by 73.3%. The improvement of the interfacial interaction of the modified fiber and rubber matrix was considered to be one of the essential reasons.