| Traditional UV-curable unsaturated polyester has many disadvantages such as low curing-velocity, high curing shrinkage rate, poor film adhesion, bad pliablity and low anti-impact strength which hinder the application of the unsaturated polyester in the energy-saving and environmental area of UV-curing. To solve those problems, in this paper, UV-curable unsaturated polyester-urea resin was prepared by melt polymerization, and the properties of the resin and coatings were studied. This paper has practical significance for developing and expanding the application of the unsaturated polyester in the UV-curable pantings.The main contents of of this papar are as followes:(1) By changing the rate between saturated dicarboxylic acid and unsaturated dicarboxylic acid, the addition levels of dimer acid and urea, and the kind of the diols, many types of resins were prepared using melt polymerization. The properties of there resins were studied. It was found that the molecular weight was increased with the addition of dimer acid, which caused the improvement of the comprehensive performance of the coating , but a lightly increasing of the viscosity at the same time. The effect of acid value upon the cured film performance was discussed. It was found that when the acid value of the reaction mixture reached 30, the cured film could have excellent mechanical properties and water resistance, and the viscosity maintained at low level.(2) The influence of resins, photoinitiators, reactive diluents, inhibitors and UV radiation sources upon curing velocity and curing degree were studied. The results showed that when the amount of urea was 0.04mol, the saturated dicarboxylic acid/ unsaturated dicarboxylic acid ratio was 1:9, D-1173 as the photoinitiator with the amout of 4%～6%, MMA as reactive diluent with the amout of 50% wt of resin, the dosage of inhibitor 1,4-dihydroxy-benzene was 0.015%, the curing speed was very fast with a curing time of 40s, simultaneously, the paint with relatively low viscosity had long storage life.(3) Many properties of the coating such as hardness, anti-impact strength, adhesion and water resistance were measured. The influence of resins and active diluent on these properties were discussed. It was found that dimer acid could improve anti-impact strength more effectively than diols with flexible molecule chain(DEG and DPG). It was also found that when the amout of dimer acid was 0.04mol and MMA as reactive diluent with the concentration of 50% wt of resin, the anti-impact strength of coatings was more than 40kg﹒cm, the hardness was 5H, and the curing shrinkage rate falled from 8.3% of the traditional unsaturated polyester to 4.1%, the adhesion could rearch grade 1 and the coatings exhibited excellent water resistence. Through the TG/DSC, it can be found that the coating has excellent thermal stability.
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