Improved interfacial shear strength of CF/PA6 and CF/epoxy composites by grafting graphene oxide onto carbon fiber surface with hyperbranched polyglycerol

The interfacial properties between carbon fiber (CF) and polymer matrix are critical to the performance of CF reinforced composites. Herein, we reported a new method of tailoring the interfacial properties by grafting graphene oxide (GO) onto the CF surface with hyperbranched polyglycerol (HPG), which could improve the interfacial shear strength (IFSS) and heat resistance of CF/PA6 and CF/epoxy (EP) composites. A large number of hydroxyl groups were introduced onto CF surface by using HPG as a new coupling agent, which improved the grafting amount of GO, the polarity, wettability and surface energy of CF. The IFSS of composites at different temperature was investigated by microbond test. The results showed that after introducing GO into the interface, the IFSS of CF reinforced PA6 and epoxy composites increased by 44% and more than 30%, respectively. Moreover, the IFSS of GO modified CF/EP1 composites at 85°C was only 9.1% lower than that at 25°C. In addition, the IFSS of the CF/PA6 and CF/EP2 composites could be kept stable when the ambient temperature was lower than the melting point or glass transition temperature of the resin matrix. Finally, the interfacial enhancement mechanism was further analyzed in details.