The Synthesis Of Novel Photosensitive Prepolymers And Its Application In Coating

UV curing technology has been developing rapidly for its enabling, energy saving, efficient, economical and environmental friendly etc. This article innovatively discussed two synthesis routes of multi-functional UV-Curable PUA , then synthesized several kinds of multi-functional polyurethane acrylate resin,two kinds of hyperbranched polyurethane acrylate resin, and inspected their photo-curing performance.In part one, a six functional UV-curable polyurethane acrylate pre-polyme(rSPUA) was synthesized by pre-process capped and post-process capped routes using isophorone diisocyanate (IPDI), polyether-tribasic alcohol(PE-3OH), and trihydroxy propane diacrylate (TMPDA). The properties of two resins from different synthesis routes were compared by molecular weight, molecular weight distribution, viscosity and their film properties such as hardness, Tg and so on. The results were as follows: SPUA2 prepared by the pre-process capped route had lower molecular weight, lower viscosity, higher curing activity and higher film hardness than SPUA1, which was prepared by the post-process capped route, the performance of SPUA2 was better. The better reaction conditions of SPUA2 were studied, in terms of the influence of reaction temperature, reaction time, catalyst and inhibitor. The better reaction conditions were as follows: the formula ratio was n(IPDI):n(TMPDA):n[PE-3OH]=3:3.15:1, the inhibitor was 4-methoxy-phenol and the content was 1.1% wt; in the first step, the catalyst content was 0.15% wt; the reaction temperature was 45℃; the reaction time was 6h;in the second step, the catalyst content was 0.25%wt; the reaction temperature was 65~70℃; the reaction time was 6 h.In part two, several kinds of muti-fuctional polyurethane acrylate(PUA) were synthesized, and the effect of different types of polyether tri-basic alcohol (PE-3OH) and molecular weight of PE-3OH on curing and mechanical properties of the curing membrane were studied. The effects of amount of photoinitiator and diluent on the curing performance of polyether six fuctional PUA were also studied. A better film-forming formula was designed.The self-made and commodity PUA were compared. The results were as follows: in three types of PE-3OH,the polyether six fuctional PUA made by PE-3OH 900 had the lowest viscosity, and its curing membrane had excellent curing and mechanical properties.With the molecular weight of PE-3OH increasing , the resin had smaller viscosity,longer curing time,and its curing membrane had lower hardness,flexibility and elongation, but higher tensile strength. As the photoinitiator content increased, the curing speed increased. With the diluent content increased, the curing speed and hardness of the film increasd, but the flexibility declined.On two types of substrate, the film hardness measured on the metal plate was relatively higher,and the flexibility and adhesion of film measured on PVC was better.The designed formula coating had faster curing speed,higher hardness,but slightly decreased flexibility. Compared with commodity PUA, the six functional polyether PUA had relatively lower curing speed and curing membrane hardness, but better flexibility and adhesion.In part three, two branched polyester HBPE-OH containing eight hydroxyl groups was synthesized using pentaerythritol as a "center core" with two different routes. Route one: the compound of HBPE-COOH1 with eight carboxyl groups was synthesized through the reaction of pentaerythritol and trimellitic anhydride, then the propylene oxide reacted with carboxyl groups of HBPE-COOH1, thus the branched polyester HBPE-OH1 was abtained. Route two: the compound of HBPE-COOH2 with four carboxyl groups was synthesized through the reaction of pentaerythritol and phthalic anhydride, then the glycidol reacted with hydroxyl groups of HBPE-COOH2, thus the branched polyester HBPE-OH2 was abtained.Then, the prepolymer IPDI-TMPDA was synthesized through the reaction of trimethylolpropane diacrylate (TMPDA) and isophorone-diisocyanate (IPDI). Then the two different branched polyester reacted with prepolymer (IPDI-TMPDA) separately, thus two kinds of reactive acryloyl oxygen capped branched polyurethane acrylate HUA1 and HUA2 were abtained. The structures of HUA1 and HUA2 were characterized by FT-IR. Their glass transition temperatures were measured by DSC. The effects of different temperature and different diluent (HDDA) content on the viscosity of resin were discussed. The results were as follows: with temperature and the HDDA content increasing, the resin viscosity gradually decreased, and at the same condition, the viscosity of resin HUA1 was higher than HUA2. The performance of their UV-curable film was studied; the results showed that the coating had high curing rate and hardness on iron substrate.