Preparation and properties of one-component self-cross-linking stabilized epoxy-acrylate composite emulsion

Against at the contradiction between their stability and the corrosion resistance of epoxy-acrylate composite emulsion, the modified epoxy containing terminal double bond and retaining partial epoxy group was gained using active hydrogen acrylic monomers to react with epoxy resin. Then, a three-layer waterborne epoxy-acrylate composite emulsion which contains modified epoxy resin acrylate polymer(core)-inert polyacrylate(middle)-carboxyl acrylate polymer(shell) structure was prepared using emulsion polymerization via structure design idea. By studying the influence of the content of the modified epoxy resin in the core layer and methyl acrylic acid (MAA) in the shell layer of the latex particle on the composite emulsion stability and corrosion resistance controllability, a suitable composition was determined. The structure of the obtained latex was characterized by FTIR and TEM. The stability of the composite latex was characterized by zeta potential, average particle size, and storage stability. And the corrosion resistance of the composite latex films was analyzed by electrochemical AC impedance spectroscopy and salt spray tests. In addition, the self-cross-linking behavior and properties of composite emulsion were studied. The results showed that the epoxy-acrylate composite emulsion with best stability and corrosion resistance was obtained when the modified epoxy resin in the core layer was 10 wt% and MAA in the shell layer was 1wt% of the total monomer weight. This film exhibited a Rct value 1.49 x 107 & omega; cm2 after being soaked in 3.5wt% NaCl for 1 day and dropped by one order of magnitude after 7 days. The FTIR, DSC, and SEM results reveal that self-cross-linking reaction occurs between epoxy groups in the core layer with carboxyl groups in the shell layer during film formation. The outstanding stability as well as corrosion resistance is attributable to the cross-linking reticulation structure. It is a new strategy for improving the corrosion resistance of the film through emulsion's intrinsic properties.