Evaluation of scratch resistance of functionalized graphene oxide/polysiloxane nanocomposite coatings

Functionalized graphene oxide (FGO) was synthesized with 3-glycidoxy-propyl trimethoxy silane (GPTMS) and subsequently incorporated into polysiloxane coatings to improve the mechanical properties, especially scratch resistance, through the sol-gel and epoxy/amino curing reactions. The surface functionalization of graphene oxide (GO) was evidenced by TEM, FTIR and XPS. FGO was found to have better compatibility and establish stronger interface with polysiloxane matrix than GO based on the observed microstructures using OM and SEM. Nanoindentation, macro scratch and progressive load scratch tests were employed to assess the mechanical performance of FGO/polysiloxane nanocomposite coatings, demonstrating significant improvement in comparison with either the pure polysiloxane or the GO/polysiloxane coatings. A 40% enhancement on microhardness (233 MPa), 83% improvement of scratch resistance (1100 g) and 144% increase in 1st scratch critical normal load (4.88N) are achieved by addition of only 0.75 wt% of FGO. Furthermore, elastic recovery and scratch damage morphology were investigated to provide insight into scratch behavior and reinforcement mechanism.