Preparation And Application Of UV-Curable Waterborne Polyurethane-based Emulsion

In order to improve the comprehensive performance of UV-cured waterborne polyurethane coatings,polyurethane-acrylate(PUA)oligomer terminated with multiple unsaturated bonds was prepared using isophorone diisocyanate(IPDI),methylene diphenyl diisocyanate(MDI)and polyols as monomers,using2,2-dimethylol propionic acid(DMPA)as hydrophilic chain extender,together with pentaerythritol triacrylate(PETA)as end-capper.The UV curable waterborne polyurethane acrylate(UV-WPUA)composite emulsion was obtained by mixing the PUA oligomer with certain content of reactive diluents(DPHA and DPGDA)and then dispersing the mixture in water.The molecular structure of the polyurethane prepolymer,PUA oligomer and UV-cured polymer was investigated by FT-IR.The influence of the composition and content of the diluents and end-capper on UV-WPUA properties,including the emulsion stability,thermal property,water resistance,adhesion,hardness,glossiness of polymer film were studied.The results show that the WPUA emulsion has excellent stability and the UV-cured film features good hardness and remarkable water resistance when PETA is used as end-capper and the end-capped ratio of the polyurethane prepolymer is 70% and DPHA/DPGDA(mass ratio 1:1)is used as diluent.Besides,the polyurethane prepolymer was modified by bisphenol A epoxy resin E-51.The UV curable waterborne polyurethane capped with HEA was synthesized by isophorone diisocyanate(IPDI),methylene diphenyl diisocyanate(MDI),polyols and2,2-dimethylol propionic acid(DMPA)as hydrophilic chain extender,E-51 as modifier.The effect of E-51 on the properties of the modified aqueous polyurethane emulsion and UV cured film was studied,including the emulsion stability,thermal property,water resistance,adhesion,hardness,glossiness of polymer film.it is found that the thermostability,water resistance,hardness and adhesion has been improved by the modification of E-51.The optimal content of E-51 in the hybrid emulsion was7wt%.