A novel electrically conductive water borne epoxy nanocomposite coating based on graphene: facile method and high efficient graphene dispersion

[Display omitted] •High concentrated graphene nanosheets dispersion (20 mg/ml) in water was synthesized.•Electrical conductivity as high as 0.5 S/m at graphene loading level of 1.5 wt% was obtained.•A Facile processing method was used to fabricate conductive coatings.•High electrical permittivity values were achieved at graphene loading level of 1.5 wt%. In this work, we present a novel method to exfoliate graphite to graphene oxide nanosheets with single to 3 layers at concentration as high as 15 mg/ml. In the first step, graphite intercalated compound (GIC) was obtained through a chemical intercalation process. In the next step, GIC was expanded and used as the precursor to obtain oxidized graphite. Oxidized graphite was introduced into a high alkaline medium and a high-speed homogenizer was used to complete the exfoliation process. Raman spectroscopy, XPS, XRD, TGA, SEM and TEM were used to characterize the synthesized graphene oxide nanosheets. Electrically conductive coatings were prepared by adding and stirring graphene oxide dispersion into an epoxy-hardener pre-mixture. The prepared coatings were post cured at 100 °C followed by annealing at 225 °C to in situ reduce the incorporated graphene oxide to graphene nanosheets. High electrical conductivity values as 0.5 S/m was obtained for the epoxy-graphene nanocomposite at graphene loading level of 1.5 wt%, which is comparable to previously reported data using more complex and laborious fabrication methods. Cryo-SEM images were captured in the liquid phase to investigate electrical network formation in the polymeric matrix.