Improving mechanical and thermal properties of short carbon fiber/polyamide 6 composites through a polydopamine/nano-silica interface layer

Carbon fiber (CF) reinforced matrix composites have been applied widely, however, the interfacial adhesion of composites is weak due to smooth and chemically inert of CF surface. To solve this problem, A polydopamine/nano-silica (PDA-SiO2) interfacial layer on carbon fiber surface was constructed via polydopamine and nano- SiO2 (CF-PDA-SiO2) by a facile and effective method to reinforce polyamide 6 composites (CFs/PA6). The effects of PDA-SiO2 interfacial layer on crystallization structure and behavior, thermal properties, and mechanical properties of CFs/PA6 composites were investigated. Furthermore, interfacial reinforcement mechanism of composites has been discussed. This interfacial layer greatly increased the number of active groups of CF surface and its wettability obviously. The tensile strength of CF-PDA-SiO2/PA6 composites increased by 28.09%, 19.37%, and 26.22% compared to untreated-CF/PA6, CF-PDA/PA6, and CF-SiO2/PA6 composites, respectively, which might be caused by the increased interfacial adhesion between CF and PA6 matrix. The thermal stability, crystallization temperature, crystallinity, and glass transition temperature (T-g) of CF-PDA-SiO2/PA6 composites improved correspondingly, attributing to the heterogeneous nucleation of nano-SiO2 in the crystalline area and hydrogen bonds with molecular chains of PA6 in the amorphous area. This work provides a novel strategy for the construction of interfaces suitable for advanced CF composites with different structures.