Preparation of waterborne epoxy dispersion and its application in 2K waterborne epoxy coatings

Waterborne epoxy dispersions have excellent permeability and adhesion to various polar substrates and they are widely used as coatings and adhesives in industrial applications. Herein we present experimental schemes of a reactive emulsifier and three waterborne epoxy dispersions prepared for waterborne epoxy coatings. First, the epoxy groups in polyethylene glycol diglycidyl ether (PEGDGE) and epoxy resin E20 are ring-opened with amino hydrogen in ethanolamine, followed by neutralizing with glacial acetic acid (HAc) to obtain an emulsifier for emulsifying epoxy resins. Then two bisphenol A epoxy resins E20, E51 and a novolac epoxy resin NPPN631 are employed as emulsified oil phase to prepare waterborne epoxy dispersions with the above emulsifier. And finally the as-prepared waterborne epoxy dispersions are applied in 2K waterborne epoxy coatings. The results indicate that when the molar ratio of PEGDGE with an epoxy equivalent of 109 g▪mol−1 and epoxy resin E20 is 2:1, the synthesized emulsifier possesses the optimal emulsifying ability for epoxy resin, with the Krafft point of 56°C, and the HLB of 16. The coating films from 2K waterborne epoxy coatings occupy excellent wear resistance, thermal stability, hardness and mechanical properties. By exploring the curing mechanism, the superior performances of the coatings film prepared by waterborne epoxy dispersion and waterborne epoxy curing agent are presented.