Graphene oxide dispersion in epoxy resin prepared by direct phase transfer from ethanol: Rheology and aging

Graphene oxide addition to epoxy still presents challenges related to attaining optimized dispersion in scale-up production. Herein, the synthesis of high-quality GO by exfoliation in ethanol enabled the spontaneous phase transfer of GO from solvent to epoxy resin to produce a masterbatch with 1.5 wt.% GO content. Nanocomposites with 0.25 wt.%, 0.50 wt.% and 0.75 wt.% nanofiller contents were obtained by masterbatch dilution in epoxy resin. The results reveal the presence of a partial cross-linked network in these nanocomposites associated with the presence of GO, even without the use of a hardener. Thermogravimetric analysis showed the influence of GO on the oxidative decomposition mechanism of epoxy resin, whose behavior was assigned to strong interactions in the GO-epoxy interphase. Furthermore, the rheological behavior changes demonstrate the high quality of the GO dispersion in the resin obtained in this work. The nanocomposites showed high viscosity increases over time and pseudoplastic behavior, which was completely different from the neat epoxy resin. Aged nanocomposites without hardener present a first chemically cross-linked layer of epoxy to GO (similar to 10% for nanocomposite at 0.50 wt.% GO content) and a supramolecular coating interacting and entangled with these structures (> 40% of epoxy chains for EP-GO50).

Automated summary

This research focuses on the challenges of achieving optimized dispersion of graphene oxide (GO) in epoxy during scale-up production. The study successfully synthesized high-quality GO by exfoliation in ethanol, allowing for the spontaneous transfer of GO from the solvent to the epoxy resin. The resulting masterbatch had a GO content of 1.5 wt.%. By diluting the masterbatch in epoxy resin, nanocomposites with 0.25 wt.%, 0.50 wt.%, and 0.75 wt.% nanofiller contents were obtained. The research demonstrates the presence of a partial cross-linked network in these nanocomposites, attributed to strong interactions in the GO-epoxy interphase.