Screening the effect of graphene oxide nanosheets functionalization with ionic liquid on the mechanical properties of an epoxy coating

Epoxy coatings are widely used in many industries due to the high anti-corrosion properties, good adhesion to metals and high cross-linking density. However, due to the high brittleness and poor resistance against crack propagation, the coating performance can be decreased in exposure with external stress. In this study the graphene oxide (GO) nanosheets were modified by 1-Butyl-3-methylimidazolium chloride (BMIM-Cl) ionic liquid and then introduced into an epoxy coating for the reinforcement of the mechanical properties. The BMIM-Cl adsorption on the GO surface was studied by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis and Raman spectroscopy. The fracture surface morphology of the film without and with nanoparticles was studied by a scanning electron microscopy (SEM) to reveal the effect of GO-BMIM nanosheets dispersion on the coating mechanical properties. The GO-BMIM nanosheets were introduced into the coatings at different loadings. FT-IR test results confirmed that the BMIM molecules successfully attracted with GO sheets through physical/chemical bonds. XRD and Raman spectroscopy tests results revealed the role of BMIM molecules on the GO stacking reduction. The physical and mechanical properties of the coatings were investigated by tensile and dynamic mechanical thermal analysis (DMTA). Result showed that addition of 0.09% GO-BMIM nanosheets into the epoxy matrix significantly increased the glass transition temperature (Tg), storage modulus, tensile strength and energy at break. The coating brittleness was remarkably reduced by addition of GO-BMIM nanosheets, indicating that the BMIM molecules adsorption on the GO surface successfully improved the coating mechanical properties. Results revealed that the maximum flexural strength was obtained in the presence of 0.09% GO-BMIM, attributed to the good dispersion and high tensile strength of the nanosheets.