Fig nbsp presents the plowing hardness

fnGOr and fnSiO2 reinforced resin (Fig. 6d and e) shows residual patterns without significant damage. Indeed, fnGOr reinforced epoxies feature Droxinostat tougher response, being the residual scratch pattern characterized by some frontal and lateral pile up of a plastically displaced coating material. Superior scratch performance of fnGOr reinforced epoxies can be attributed to GOr, which physically opposes to the external loads. In addition, the organic functionalities on GOr surface (grafting polymer, residual carbonyl or hydroxyl groups) improve the dispersion acting as molecular spacers between graphene platelets, avoiding (or limiting) their re-aggregation and improving the affinity between platelets and epoxy resin in agreement with Jiang et al. [25] and Wang et al. [63]. Lastly, GOr and epoxy can form a large number of chemical bonds. These bonds improve their contact, enhancing the stress relief action of the fnGOr fillers in agreement with Kuila et al. [29]. Further, the grafting polymer on GOr increases the degree of cross-linking, thus improving the elastic modulus and stiffness of the composite material.