Reduced graphene oxide as an adhesion enhancer of fusion-bonded epoxy coatings

Alternative coating technologies based on advances in polymer engineering have been continuously developed to face the always present challenges of wear in metal surfaces. Fusion-bonded epoxy (FBE), an epoxy-based powder coating, has been widely used in some sectors due to its quick and easy application and the reduction of waste material. FBE is a high-performance composite with approximately 30 wt% microparticles, and the challenge addressed herein is to improve the coating properties by adding a low content of graphene. In this work, new coatings based on FBE and thermally reduced graphene oxide (rGO) were developed and prepared by two different processes: in one case, highly thermally stable and low functionalized graphene (rGO-tre with 4.6 % oxygenated groups) and in the other case, highly exfoliated and more functionalized graphene (rGO-tr with 9.8 % oxygenated groups). FBE/rGO-tr and FBE/rGO-tre nanocomposites were produced in concentrations of 0.1, 0.3, 0.5 and 1.0 wt% in a planetary ball mill. The coated steel plates were heated in a conventional oven at 204.C, and the curing of the material was confirmed by using differential scanning calorimetry (DSC) analysis. The addition of rGO-tr (1.0 wt%) and rGO-tre (0.5 wt%) improved the adhesion of the nanocomposite coating in the wet test by 104 % and 95 %, respectively, when compared with neat FBE coatings. Small gains in abrasion and hardness were also observed. In addition to the tendency to reduce indentation (micro and nano), it was possible to observe a better recovery of the FBE with the addition of rGO-tr and rGO-tre after the deformation carried out by the tip. The integration of graphene nanofillers of different grades in a ternary composite with silicate microparticles and epoxy powder was successfully achieved, and the adhesion, abrasion and hardness benefit from the synergy between micro- and nanofillers.