Preparation And Properties Of Waterborne Polyurethane-Acrylate-Epoxy Resin Hybrid Emulsion

In this paper,a series of waterborne polyurethane-acrylate-epoxy composite emulsions(WPUEA)have been prepared using a two-step technique including prepolymerization and dispersion of polyurethane prepolymer and in situ radical copolymerization of unsaturated monomers to improve the comprehensive performance of the waterborne polyurethane.Firstly,the polyurethane prepolymer terminated by isocyanate and bearing the carboxylic groups was prepared using diisocyanate(IPDI and MDI),polyols(PEA-2000,DL-1000,MN-500)as the monomers,using 2,2-dimethylol propionic acid(DMPA)as hydrophilic chain extender and epoxy resin(E-51)as modifier;then the prepolymer was partly blocked with pentaerythritol triacrylate(PETA),which was further blended with methyl methacrylate(MMA)and dispersed in water subsequently;finally,the in situ radical copolymerization was carried out at elevated temperature to produce a hybrid aqueous emulsion of polyurethane-acrylate-epoxy resin(WPUEA).The polymer(film)was characterized by FTIR,SEM,TEM,TG,AFM and water contact angle.The effects of the molar ratio of NCO/OH and the contents of DMPA,PETA,E-51 and MMA on the emulsion properties such as the polymer particle size,emulsion stability and film performance including the water and solvent resistance,the mechanical properties were investigated.We also compared the performance of WPU,WPUE and WPUEA.The results show that the comprehensive performance of WPUEA greatly enhanced with-NCO/OH ratio of 1.4,DMPA content of 6%~8%,terminated ratio by PETA of 25%~75%,E-51 content of 7%~9% and MMA content of 25%~30%.The TEM images show that the polymer particles have obvious core-shell structure;TG analyses show that the modified WPUEA film has higher thermal decomposition temperature than the corresponding WPU,WPUE polymer film;SEM photographs show that a certain degree of phase separation will happen between PU and PA when the dosage of MMA is too high,which is consistent with the mechanical test.The interfacial properties of WPUEA polymer film were investigated by using contact angle tester and AFM,and the results show that the modified polymer surface is more hydrophobic than those of the corresponding WPU and WPUE films.WPUEA film has enhanced resistance to water,acid,alkali,salt and organic solvents.The prepared hybrid emulsion is potential to be used in anticorrosive paints for metal surface.