The correlated effects of filler loading on the curing reaction and mechanical properties of graphene oxide reinforced epoxy nanocomposites

Graphene oxide (GO)/epoxy nanocomposites are prepared by means of the phase extraction method. FTIR and XPS characterizations have confirmed the charge transfer between GO and epoxy that promotes the uniform dispersion and exfoliation of GO. The effects of GO sheets on the curing reaction and interfacial bonding are investigated and correlated with mechanical properties of epoxy nanocomposites. The results show that the GO sheets have a facilitation effect on the curing reaction of epoxy resin, in which the oxygen groups of GO covalently react with epoxy matrix and establish chemical interfacial bonding in epoxy nanocomposites. Therefore, the mechanical properties of nanocomposites are enhanced, showing the highest tensile strength of 88.1 ± 2.5 MPa, flexural strength of 134.2 ± 6.1 MPa and flexural modulus of 3.15 ± 0.11 GPa, respectively. However, GO sheets could simultaneously physically restrict the curing reactivity and reduce the cross-link density in the interface, which results in weakened interfacial property of nanocomposites, especially at high loading. Thus, the reinforcing effect of GO sheets is reduced and the mechanical properties of GO/epoxy nanocomposites decline at relatively higher loading. Graphical abstract