Effects of hyperbranched polyamide functionalized graphene oxide on curing behaviour and mechanical properties of epoxy composites

Epoxy composites reinforced by both graphene oxide (GO) and hyperbranched polyamide (HBPA) functionalized GO (HBPA-GO) were fabricated. The effects of GO functionalization on exfoliation, dispersion state and interfacial properties were investigated. The curing kinetics and mechanisms and ultimate mechanical properties of epoxy composites were studied. The results show that the exfoliation and dispersion state of GO is significantly improved after functionalization. The functionalized GO (HBPA-GO) can effectively enhance curing reactions of epoxy matrix by reducing the activation energy due to high density of terminal primary amine groups on HBPA-GO. In addition, HBPA-GO worked as a crosslinker forming a large amount of covalent bonding with epoxy matrix through HBPA-GO/epoxy reaction and, therefore, the interfacial adhesion is enhanced, resulting in excellent mechanical properties of epoxy composites. Moreover, the interfacial properties between HBPA-GO and the epoxy matrix can be tuned by varying the temperature of the HBPA-GO/epoxy reaction before the addition of the curing agent, thereby providing a new route for the design and development of the GO reinforced epoxy composites.