Hyperbranched epoxy resin-grafted graphene oxide for efficient and all-purpose epoxy resin modification

Despite great efforts have been made on epoxy resins modification, development of additives that can be used to efficiently and universally modify epoxy composites remains a challenging task. Herein, graphene oxide (GO) sheets were covalently linked with hyperbranched epoxy resin (HBPEE-epoxy) to form HBPEE-epoxy functionalized GO (HPE-GO), which was then incorporated into epoxy resin (EP) matrix to achieve efficient and all-purpose enhancement of the properties of EPs. Compared with unmodified GO sheets, the functionalized HPE-GO sheets were better dispersed and exhibited better interfacial compatibility with the epoxy matrix, and consequently, the mechanical and thermal properties of HPE-GO/EP composites improved significantly compared to unmodified GO/EP composites. The tensile strength, flexural strength, impact strength, and fracture toughness (KIC) of EP composites containing 0.5 wt% HPE-GO increased by 65.0%, 36.2%, 259.1%, and 178.9%, respectively, compared with those for the neat EP. The storage modulus (E'), glass transition temperature (Tg), and thermal stability (T5%) also showed modest improvements. Furthermore, the HPE-GO/EP composites exhibited optimal thermal conductivities and thermal expansion properties, while maintaining higher volume resistivities compared with GO/EP composites. The results of this study support that HPE-GO is a promising, all-purpose modifier for EPs.