Construction of double grafted interfacial layer to improve thermal and mechanical properties of short carbon fiber reinforced polyamide 6 composites

Abstract A double grafted interfacial layer on CF surface was constructed via PDA and nano-SiO2 (CF-PDA-SiO2) by a facile and effective method to reinforce polyamide 6 composites (CFs/PA6). The effects of double grafted interfacial layer on crystallization structure and behavior, thermal properties, and mechanical properties of CFs/PA6 composites were investigated. This interfacial layer greatly increased the number of active groups, roughness and wettability of CF surface, 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, as well as glass transition temperature (Tg) 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. Furthermore, interfacial reinforcement mechanism of composites have been discussed.