Effect of silica nanoparticles on the curing kinetics and erosion wear of an epoxy powder coating

Abstract

In this study, the wear resistance of an epoxy powder coating was improved by SiO2 nanoparticles and their possible effect on curing kinetics of the coating was also evaluated. The epoxy powder coating was prepared with different percentages of nanoparticles (1-3 by wt.%) using a hot mixer, a method that can be more economic than other ones. The particle size distribution and Fourier-transform infrared spectroscopy (FT-IR) of epoxy powder were evaluated to examine the effect of mixing on the powder. The effect of SiO2 on the curing of epoxy powder was studied by differential scanning calorimetry (DSC). The Kissinger and model free kinetics (MFK) methods were used to calculate the activation energy (Ea) of the curing process of powders. The coating spraying process was carried out in an industrial installation on carbon steel substrates. The glass transition temperature (Tg) of the coatings was also studied using DSC. The morphology of the cured organic coatings was observed by scanning electron microscopy (SEM). Stiffness and hardness Vickers (HV) were evaluated. A test based on ASTM D969 was developed to perform erosion measurements. The results obtained by both the Kissinger and MKF methods showed that nanoparticles do not influence significantly the Ea of curing of the coatings. The addition of 1% SiO2 improves the erosion wear at 45 and 60°, due to the increase in stiffness and hardness provided by the nanoparticles, though, when particles collide at 60° with the samples, the lowest thickness loss was found for the epoxy with 3% nanoreinforcements. Keywords: Epoxy powder coating, Nanoparticles, Silica, Differential scanning calorimetry, Kinetic models, Erosion wear