| Ultraviolet(UV)curing coatings can be cured from liquid into films instantaneously when exposed to UV light,having the merit of highly efficient and energy-saving.However,they also have shortcomings such as unreacted monomer residueand some active diluents that have physiological toxicity.Waterborne coatings use water as dispersion medium,which can effectively reduce the content of organic volatiles(VOC).UV-curable waterborne coatings combine the advantages of both and have become a research hotspot.The general waterborne technology is introducing hydrophilic groups into the resin molecular chain and then performing alkali neutralization.In order to solve the problems of poor water resistance and pH stability of such coatings,the reactive emulsifiers were synthesized and UV-curing waterborne epoxy acrylate emulsions were prepared by reverse conversion method.The influence of emulsifier structure on emulsification performance was studied,and the stabilizing mechanism of emulsifiers was discussed.This study can provide theory and application basis for coatings with advantages of both environmental protection and rapid curing.Epoxy acrylate(EA)prepolymer was prepared from bisphenol A epoxy resin E-51and acrylic acid(AA)in the present of N,N-dimethylbenzylamine(BDMA).The relationship between the amount of BDMA and the esterification rate was studied and the result shows that the optimal amount of BDMA is 1.2-1.5 wt%.Photo-curable nonionic reactive emulsifiers with polyether chain segment were prepared from bisphenol A epoxy resin,polyether amine(PEA)and AA.The influences of molecular weight of nonionic emulsifier,its compounds of sodium dodecyl sulfonate(SDS)and other factors on the HLB value,critical micelle concentration(CMC)and cloud point(T_P)of the emulsifier were researched.The results show that the HLB value of the polyether nonionic emulsifier is mainly determined by the molecular weight of PEA.The higher the molecular weight of PEA,the greater the HLB value of the emulsifier,the smaller the CMC value,and the higher the TP temperature.SDS can significantly reduce the CMC value and increase its T_P temperature.The waterborne epoxy acrylate emulsion was prepared by the reverse conversion method,and the effects of the nonionic emulsifier and its compound with SDS on the performance of the emulsion system were studied.The results showed that the larger stirring rate and the amount of emulsifiermake for the smaller particle size the larger emulsion viscosity and the better stability.Photo-curable nonionic reactive emulsifiers with polyoxyethylene chain segment were prepared from bisphenol A epoxy resin,polyethylene glycol(PEG),hydroxyethyl acrylate(HEA),diallylamine(DAA)and AA.The influence of PEG molecular weight and the other factors on the HLB value,critical micelle concentration and cloud point of emulsifiers were studied.The results show that the higher the molecular weight of PEG,the larger the HLB value of the synthetic emulsifier,the smaller the CMC value,and the higher the TP temperature.The waterborne epoxy acrylate emulsion was prepared by the reverse conversion method.The effect of non-ionic emulsifier on the stability of the emulsion system was studied by orthogonal design method.The results show that the amount of emulsifier is the main factor affecting the stability of the emulsion,besides,the effects of stirring rate,emulsifying temperature and emulsifier on the stability of emulsion were successively weakened. |
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