Preparation And Properties Of UV Curable Acrylate Cathodic Electrodeposition Coatings

The UV curable cathodic electrodeposition coatings combine advantages of UV curing technology and cathodic electrophoretic coating technology together,which are reducing the curing temperature greatly,shortening the curing time,improving the curing efficiency,no influence on the shape of the coated workpiece,dense and uniform film,high utilization and environmental protection.As the resin matrix of UV curable cathodic electrophoretic coating,acrylic resin can endow the film with high gloss,good weather resistance,corrosion resistance and decorative.At present,the cathodic electrophoretic coating technology has already been well developed,but few domestic and international research on UV curable cathodic electrophoretic coating has been reported.In order to improve the water resistance and anti-acetone wipe performance of UV curable acrylate cathodic electrophoretic coating,and fill the research gap concerned about anti corrosion of UV curable acrylate cathodic electrophoretic coating,the performance of the UV curable acrylate cathodic electrophoretic coating was improved from the aspects of the resin matrix,small molecule active diluent,electrophoretic coating and curing process.All of the results were listed as bellow:Acrylate prepolymer was prepared by free radical copolymerization using OAD/DMAEMA/HEA/MMA/EHA as raw material,AIBN as initiator,and propylene glycol ether acetate as solvent.Then the prepolymer was modified with isocyano ethyl methacrylate and neutralized with lactic acid to get vinyl-containing acrylate cationic resin matrix of the UV curable cathodic electrophoretic coating.The chemical structure of the resin matrix was confirmed to be consistent with the designed structure by infrared spectroscopy.The vinyl-containing acrylate resin had a glass transition temperature of 20.46℃,5wt% heat weight loss at temperature of 240.8℃,and the maximum weight loss at temperature of 420.6℃,all of these results showed that this resin matrix had good heat resistance.The UV curable cathodic electrophoretic coating was prepared by mixing synthesized cationic acrylate resin martix with photoinitiator,deionized water and reactive diluent.The bath stability of UV curable waterborne electrophoretic coating as well as the effects of acrylate resin structure,electrophoretic coating and curing process conditions,photoinitiator dosage and multifunctional reactive diluent content on the properties of the film were studied systematically.The abtained optimal synthesis formula of acrylic resin was: 1wt% of acrylic acid eighteen ester,15wt% of 2-(Dimethylamino)ethyl methacrylate,25wt% of 2-Hydroxyethyl acrylate,23.6wt% of Methyl methacrylate,35.4wt% of 2-Ethylhexyl acrylate and 3wt% of AIBN.The molar ratio of graft monomer IEM to HEA was 0.8: 1.0,and the neutralization degree of tertiary amine in acrylate resin was 80%.The optimal solid content of coating,electrophoresis voltage,electrophoresis time and UV curing time were 10wt%,30 V,60s.and 60 s,respectively.The concentration of photoinitiators in the film was 4wt% with a combination of 1173 and 184 at a mass ratio of 1: 1.The optimal dosage of diluent PETA was 20wt%.Under this optimum condition,a smooth electrophoretic film with excellent performances,such as 2 level in adhesion ability,4H of hardness,more than 1500 times of acetone wiping resistance,and good resistance against water,acid and alkali,was obtained.A novel fluorinated dimethacrylate monomer FUDMA was synthesized using IPDI,2-Isocyanato-ethyl methacrylate and 2,2,3,3,4,4,5,5-Octafluoro-1,6-hexanediol as raw materials.Infrared and nuclear magnetic spectrum confirmed that FUDMA was synthesized successively as designed.The fluorine-containing methacrylate monomer FUDMA was used as a diluent and mixed with cationic acrylate resin martix to prepare the UV curable cathodic electrophoretic coating.The addition of FUDMA could significantly improve the hydrophobicity,acetone wiping resistance,corrosion resistance and salt water resistance of the film.However,the stability of water-based electrophoretic coating bath would be reduced.The FUDMA dosage should be controlled around 20wt%.