Enhanced mechanical properties of epoxy nanocomposites with mildly surface-functionalized graphene oxide by tuned amine species

The surface functionalization of graphene oxide (GO) is always attractive in modulating the interfacial characteristics, improving the interfacial bonds and mechanical properties of epoxy-based nanocomposites. In this contribution, amine functionalized graphene oxide (AGO) samples were prepared through the surface functionalization of GO using m-xylylenediamine (m-XDA) and polyetheramine D230, respectively. Simultaneously, weakly oxidized and normally oxidized GO samples were both functionalized to obtain AGO samples with low and high amine grafting density. AGO/epoxy nanocomposites were fabricated and their mechanical properties at room temperature (RT) and liquid nitrogen temperature (LNT) were investigated. Interfacial characteristics of the nanocomposites were revealed through experimental and molecular dynamics (MD) simulation methods. It was found that m-XDA grafted GO (MAGO) showed better dispersion in the matrix and prominently higher efficiency in enhancing the mechanical properties of epoxy resin than D230 grafted GO (DAGO). MAGO nanocomposites exhibited tensile strength 18.1% and 11.3% higher than neat epoxy at RT and LNT, respectively. The result was highly consistent with the enhanced interfacial interaction energy between MAGO and epoxy compared to that between DAGO and epoxy as revealed by MD simulation. However, nanocomposites modified by AGO with improved amine grafting density didn't show enhanced mechanical properties as expected from MD simulation.

Automated summary

Different methods of surface functionalization of graphene oxide with varying amine grafting densities were studied in this research to prepare corresponding nanocomposites. It was found that graphene oxide functionalized with m-xylylenediamine showed better enhancement of mechanical properties in epoxy resin compared to graphene oxide functionalized with polyetheramine D230. However, nanocomposites modified with graphene oxide with improved amine grafting density did not exhibit the expected enhancement in mechanical properties as revealed by molecular dynamics simulations.