Waterborne Epoxy/Acrylic Resins Stabilized through the Neutralization of Basic Amine-Modified Epoxy and Acidic Acrylic Copolymers

In this work, a class of stable waterborne epoxy/acrylic resins with high performance is prepared through the simple blending of modified epoxy and acrylic copolymers. The bisphenol A-based epoxy resin is end-modified with ethanolamine (ETA) while the acrylic copolymers are synthesized with methyl methacrylate (MMA), glycidyl methacrylate (GMA) bearing epoxide, and methacrylic acid (MAA) bearing carboxylic acid. The mixtures of the modified epoxy and acrylic copolymers, both with molar masses above 10,000 g/mol and insoluble in water, can be successfully emulsified without additional dispersants. The key is that ETAs on the modified epoxy provide a basic condition to promote dissociation of the carboxylic acids on the acrylics in water, leading to the electrostatic stabilization. The particle size of the emulsions is less than 300 nm, and the emulsions are stable after storage for more than 9 months. The epoxy/acrylic resins are cross-linkable and show good thermal properties, with a high glass-transition temperature (Tg) up to 104.6 °C and a thermal degradation temperature (Td) up to 330.4 °C. The application of the resins as the surface coating of steel was demonstrated, and the films exhibit a good corrosion resistance, less than 5% rusted area on the steel surface after 5-h salt spray test.