Due to their different molecular structures, epoxy resins (EP) can exhibit different properties. And because it is easy to be mixed with different curing agents, diluents, auxiliaries, etc., to prepare epoxy resin materials with excellent mechanical, mechanical, thermal, adhesion, insulation and anti-corrosion properties, so as to be widely used in anti-corrosion coatings. 

      However, with the complication of the application environment, the simple EP coatings show some deficiencies: First, due to the low thermal conductivity, resulting in poor heat resistance, most EP is only suitable for the environment below 100 °C; Second, due to the high cross-link density after curing, result in high friction coefficient and poor wear resistance and impact resistance. Third, the high resistivity is prone to electrostatic effects; the fourth is that it is prone to defects after curing, which affects the corrosion resistance. To better utilize the advantages of EP, fillers are often added to improve performance.

      Nano Graphene has great potential in improving the properties of resin-based materials due to its unique crystal structure and excellent physical properties and its derivatives can initiate the polymerization reaction. Since graphene has a large specific surface area and a high surface energy, it is easily agglomerated when added as a filler to an epoxy resin, thereby affecting the performance of the coating. 

      In order to evenly disperse graphene into epoxy matrix, scholars have conducted a lot of research. From the initial simple mixing, ultrasonic dispersion technology was developed, and a silane coupling agent was used to improve the adhesion and compatibility between graphene and epoxy resin. It was found that the addition of nano graphene improves the performance of the coating, but when added to a certain amount, the accumulation of graphene will affect the further improvement of the coating performance. In recent years, some scholars have prepared functionalized graphene by functional group modification on the surface of graphene. It was found that while retaining the graphene-based properties, it can improve the adhesion to the epoxy matrix, which makes research on graphene/epoxy resin composite coatings have made new progress.

      From the thermal performance point of view, graphene is the material with the highest thermal conductivity currently known (a single layer is about 5000W/mK), as a filler can increase the heat resistance of epoxy; from the mechanical and mechanical properties, graphene is composed of sp2 hybrid planar carbon atoms. It has high modulus, high strength, and low shear force and low friction coefficient between graphene layers. It is easy to transfer to the epoxy coating surface to form a transfer film.

       After being combined with epoxy, the wear resistance and impact resistance of the coating can be improved; from the viewpoint of electrical properties, the theoretical resistivity of the graphene monolayer is approximately 10-6 Ω·m, and due to its low bulk density, a small amount of graphene can be added to the epoxy resin with good conductivity; from the viewpoint of anti-corrosion performance, because of the small size effect of graphene and two-dimensional laminar structure, the defects in epoxy coating can be improved so that it can form dense insulation layer in the coating, thus reducing corrosion.

by Jemma Liang