The role of functionalized graphene oxide on the mechanical and anti-corrosion properties of polyurethane coating

Abstract

Polyurethane (PU) has been commonly used in a wide range of applications due to its high flexibility and good UV resistance. Attempts have been extensively carried out to improve the corrosion resistance and mechanical properties of this coating through inclusion of nanomaterials. In this study the graphene oxide nanosheets, covalently functionalized by (3-glycidyloxypropyl) trimethoxysilane, were introduced into the PU matrix to enhance the mentioned weaknesses. The modified (fGO) and unmodified-graphene oxide nanosheets (GO) were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis, field emission-scanning electron microscopy (FE-SEM), UV–vis and thermal gravimetric analysis (TGA). The physical–mechanical properties of the PU coatings reinforced with GO and fGO nanosheets were characterized by dynamic mechanical thermal analysis (DMTA) and tensile test. The influence of GO and fGO nanosheets on the fractured surface morphology of the PU coating after tensile test was studied by SEM analysis. In addition, the corrosion protection properties of the mild steel panels coated with PU coatings were characterized by salt spray test and electrochemical impedance spectroscopy (EIS). The results affirmed the physical–mechanical and anti-corrosion properties enhancement of the PU coating after incorporation of fGO nanosheets. The tensile stress, energy at break, loss factor and storage modulus values were significantly increased by addition of fGO nanosheets. The fGO stability and dispersion in the PU matrix was improved after modification with (3-glycidyloxypropyl) trimethoxysilane. The interfacial bonds between the polyurethane coating-fGO nanosheets were significantly enhanced. Besides the experiments, theoretical quantum mechanics approaches were utilized to examine the interactions of trimethoxysilane with polyurethane and GO surface.