Stable waterborne epoxy emulsions and the effect of silica nanoparticles on their coatings properties

Abstract

The aim of this study was to prepare stable waterborne epoxy emulsions and study the properties of their corresponding coatings containing different contents of silica nanoparticles. For this purpose and in the first step, the stabilizing effect of various amounts of an acrylate terpolymer latex (poly (methyl methacrylate-co-butyl acrylate-co-acrylic acid)) and a non-ionic emulsifier (nonyl phenol ethoxylates 20 emulsifier (known as Kenon 20)) on waterborne epoxy emulsions was explored. The results indicated that the emulsion containing 5 wt.% latex and 6 wt.% Kenon 20 (EK6A5) was the most stable. In the next step, silica nanoparticles with 1, 2, 3, and 4 wt.% were added to EK6A5 emulsion. It was found that addition of nanoparticles up to 3 wt.% improved the stability. Finally, the pure and nanoparticle contained emulsions were coated on a steel substrate and their adhesion performance, pencil hardness, surface wettability, and wear and corrosion resistance were investigated. The comparison between the samples with and without silica nanoparticles revealed enhanced properties such as adhesion strength (up to 5B), wear resistance, corrosion resistance (degree of blistering up to 8 F and mean rust creepage up to 10), and increased contact angle (up to 63°), by addition of proper amounts of silica nanoparticles (up to 3 wt.%).