Epoxy-acrylic microgels in electrodeposition coating films

Epoxy-acrylic microgels (EAM) have been prepared via an aqueous dispersion polymerization of a mixture of acrylic monomers in the presence of the cationic soap with the quaternary ammonium salt groups and 2,2′-azobis(2-methylpropionitrile) (AIBN) as an initiator. The prepared microgels have a bimodal particle size distribution of 10 and 52 nm, and consist of a cross-linked acrylic polymer and cationic epoxy resin. Rheological data from the pendulum type rheovibron show that the presence of the spherical microgels in electrodeposition paint perturbs the flow of the surrounding fluid in a low shear field. A scanning electron microscope (SEM) showed that edge protection (%) at a knife blade increased proportionally with the amount of the microgel in the coating formulation. The microgels also provided excellent corrosion resistance; the cured film containing more than 7% microgels was free of rust spots after 168 h of the salt fog spray test. These results lead to the conclusion that EAM has a remarkable ability to perturb the thermal flow during the curing process and can be used in electrodeposition coating formulations to provide edge protection.