The influence of dicarboxylic acid derivatives synthesized with different anhydride structures on the performance of waterborne epoxy coatings

Carboxyl-based compounds are widely used to toughen waterborne epoxy coatings due to their excellent compatibility. However, achieving toughening without sacrificing the performance of epoxy resin systems still requires further research and development. This study addresses this challenge through molecular structure design. A series of dicarboxylic acid derivatives were synthesized by reacting four different chain segment structures of anhydride compounds with neopentyl glycol (NPG). 1 HNMR confirmed its successful synthesis, and the structural characteristics and reactivity of the dicarboxylic acid derivatives were analyzed through molecular simulation. We systematically investigated the effects of these dicarboxylic acid derivatives, derived from different molecular segments, on the fundamental physicochemical properties of the waterborne epoxy resin, as well as on the performance of the cured films and the resulting coatings. Results showed that the dicarboxylic acid derivatives NP prepared by the reaction of phthalic anhydride with NPG has the best modification effect. The NP-modified waterborne epoxy resin demonstrated excellent storage stability and a small particle size. Furthermore, it not only improved the mechanical and thermal properties of the cured film but also significantly enhanced the acid, water, and salt spray resistance of an epoxy primer without compromising other key characteristics. This research strategy provides strong guidance for developing high performance waterborne epoxy resins and coatings by tailoring the molecular structure of the modifier.