The Rheology of Graphene Oxide Dispersions in Highly Viscous Epoxy Resin: The Anomalies in Properties as Advantages for Developing Film Binders

Graphene oxide (GO) has been successfully used as a filler to modify various properties of polymers and fiber-reinforced composites. The resulting properties depend on the filler content and on the distribution of GO in the polymer matrix. In this work, for the first time, we introduced GO into the highly viscous DEN-438 epoxy novolac resin and investigated rheological properties of the resulting compositions. In particular, we studied the functions of complex viscosity, storage and loss moduli, and mechanical loss tangent on temperature and GO content. The unusual behavior of the newly prepared formulations compared to typical GO/epoxy mixtures was discovered. At low GO content, introduction of GO led not to an increase, but to a decrease in the resin viscosity, with the minimum registered at 0.29 wt.% GO. After this threshold value, viscosity increased with GO content, which we explained by formation of the liquid crystalline structure. At higher GO concentrations, the formulations changed their state from solid-like at rest to liquid-like under load, with the properties being highly desired for film binders. The discovered properties of the GO/novolac epoxy resin formulations suggest their potential use as the new generation of film binders for Resin Film Infusion technology.