Synthesis of dicarboxylic acid compound structurally analogous to bisphenol A: for development of stable waterborne epoxy coatings

The use of bisphenol A (BPA) in traditional waterborne epoxy coating formulations is harmful to human health, and the low toughness of the cured film severely limits its application in many areas. Most BPA alternatives enhance the toughness of the epoxy cured film but compromise the coating's properties to varying degrees. Therefore, developing a BPA alternative that toughens epoxy resins without sacrificing modulus and mechanical strength remains a significant challenge. In this study, we synthesized dicarboxylic acid compound (PNP) with a structure similar to BPA, using phthalic anhydride and neopentyl glycol. This compound serves as a substitute for BPA. We systematically explored the influence of different PNP contents on the performance of waterborne epoxy resins and coatings. The results showed that PNP is more conducive to preparing waterborne epoxy resins with smaller particle sizes and stable heat storage. Compared with BPA-modified epoxy resin, PNP significantly increases the elongation at break and tensile strength of the cured film. Moreover, different PNP contents can significantly improve the coating's impact resistance, pull-off adhesion, water resistance, salt spray resistance, and acid resistance without affecting other mechanical properties and alkali resistance. This study provides a new perspective for preparing environmentally friendly, high-performance, tough, and stable waterborne epoxy coatings.