Epoxy/polyurethane hybrid nanocomposite coatings reinforced with MWCNTs and SiO2 nanoparticles: Processing, mechanical properties and wear behavior

Abstract

The present paper aims to introduce a novel approach to fabricate hybrid polymer nanocomposite coating containing epoxy/polyurethane blend, multi-walled carbon nanotubes (MWCNTs) and SiO2 nanoparticles. For this purpose, MWCNTs and SiO2 nanoparticles were first functionalized with silane and silyl compounds, respectively, and then mixed with epoxy resin and polyurethane prepolymer along with dimethylthiotoluenediamine (DMTDA) as hardener. Eventually, the nanocomposite coatings containing 0–0.75 wt% of MWCNTs and 0–2.5 wt% of SiO2 nanoparticles was sprayed on carbon steel plates, poured on appropriate dies and analyzed using Fourier Transform Infrared Spectroscopy (FTIR), pull off, hardness, tensile, impact and wear tests. Moreover, surface roughness and wear mechanisms were tested using Scanning Tunneling Microscopy (STM) and Scanning Electron Microscopy (SEM), respectively. It has been shown that reinforcing of the matrix with inappropriate amount of nanoparticles (NPs) will negatively effect on the samples' pull off strength, hardness, and modulus of elasticity. However, in case of using the hybrid of 0.75 wt% MWCNTs and 0.75 wt% SiO2 NPs, the modification will be ended in the least impact strength and surface roughness along with about 600% of increase in the elastic modulus. Furthermore, sample with 0.75 wt% MWCNTs and 2.5 wt% SiO2 nanoparticles exhibited the highest hardness/elastic modulus ratio (59.23) and approximately 600% increase in wear resistance. Finally, voids elongation and joining were identified as the main wear mechanisms for the toughened samples.