One-step surface modification of graphene oxide and influence of its particle size on the properties of graphene oxide/epoxy resin nanocomposites

[Display omitted] •Graphene oxide is used without drying after the synthesis.•Surface of GO is modified with curing agent.•Selective plasma etching was used to characterize GO dispersion in epoxy.•The influence of GO particle size on properties of nanocomposites is determined. Graphene oxide (GO) was synthesized from expanded graphite with particle size of 130 μm (GO130) and 1200 μm (GO1200) and characterized. GO130 was oxidized to a higher degree and contained larger concentration of CO bonds. After the synthesis, the GO was kept in a form of viscous slurry in methanol to prevent formation of graphite oxide. The slurry was mixed with a hardener and methanol was evaporated. The nanocomposites with GO content from 0.25 to 1.0 wt% were prepared by mixing the epoxy resin, hardener and hardener/GO mixture and cured. The particles were homogeneously distributed within the polymer matrix as observed by SEM on the plasma etched samples. The glass transition temperature increased from 81 °C to up to 90 °C. The Young’s modulus increased by 35% and 30% with the addition of GO130 and GO1200, respectively, while the tensile strength increased for 10% only when GO1200 had been added. The optimum concentration of GO in the nanocomposite is from 0.25 to 0.50 wt%.