Enhancement of mechanical and self-healing ability of Diels-Alder based epoxy coating using functionalized nano-silica

In this study, the interfacial and matrix healing of Diels Alder (DA)-based hybrid epoxy polymer coating have been investigated using self-healing enabled silica nanoparticles as nanofiller. The silica nanoparticles prepared with the sol-gel method were grafted with furfuryl amine functional group to enable the self-healing properties. The hybrid epoxy polymer nanocomposites with 0.5, 1, and 2 wt.% of furfuryl functionalized silica nanoparticles were prepared by adding irreversible epoxy resin and reversible DA-based epoxy resin to enhance both the self-healing and mechanical properties. Successful functionalization of silica nanoparticles was confirmed by FTIR spectroscopy and the surface morphologies before and after functionalization were investigated by FESEM analysis. The formation of thermo-reversible DA and retro-DA polymer networks was confirmed from DSC analysis, and the thermal stability of the composites was investigated from TGA analysis. From DSC plots, the enthalpy change observed near ∼80°C and ∼140°C revealed successful DA and retro-DA thermo-reversible reaction. The TGA analysis showed improvement in thermal stability till 1.0 wt.% filler loading. The tensile strength and flexural strength of the nanocomposites were improved by ∼58% and ∼30%, respectively, for 0.5 wt.% filler-loaded nanocomposites (FBC0.5) with respect to control samples. The healing behaviour of epoxy coating on steel substrate was investigated through a scratch healing test and showed ∼93% healing efficiency with 0.5 wt.% filler loading, whereas epoxy composite without filler showed ∼59% healing efficiency. Fracture behaviour of the nanocomposites under tensile loading was analysed through SEM analysis. This study espouses the potential use of furfuryl amine functionalized silica nanoparticles for healing of epoxy coating when applied with a hybrid polymer matrix.