Study On Synthesis And Curing Properties Of UV-curable Polyurethane Acrylate Emulsion

The current research of low pollutional and environment-friendly coatings mainlyfocus on four directions which including waterborne coatings, powder coatings, highsolid coatings and radiation curing coatings, and the development of waterbornecoatings and radiation curing coatings are most features among the four coatings.Becsuse the latent heat of evaporation of water is high, the curing rate of waterbornecoatings is slow. The curing speed of UV-curable coatings is high, but a large numberof reactive diluent damages the operator’s health, and residual monomers affect thelong-term properties of coating.In this study, the preparation of the waterborne UV-curable PUA emulsioncombine the traditional technology of waterborne coating and the technology ofUV-curable. It not only shortens the drying time of waterborne coatings, but alsoreduces the amount of reactive diluent which in the traditional UV-curable coatings.The polyurethane-acrylate (PUA) emulsion with photosensitive properties wassynthesized by the main raw materials, which including anti-yellowing of isophoronediisocyanate (IPDI)，the excellent flexibility of polyether binary alcohol (DL-1000)，the dimethylol propionic acid (DMPA) with hydrophilic groups and the methylacrylate-β-hydroxyethyl methacrylate (HEMA) which can introduce C=C doublebonds. IPDI, DL-1000and DMPA and so on synthesized the PU part of the PUAprepolymer, and then the HEMA as the PA part end up the chain,which introducedC=C double bonds and made the prepolymer have photosensitive properties. At last,PUA emulsion was obtained by neutralizing with amine and dispersing prepolymer inwater. The PUA complex mixture with photosensitive properties was obtained bymixing of the emulsion, reactive diluent tripropylene glycol diacrylate (TPGDA)andphotoinitiator,which can transformed intocompound film by UV curing reaction.The influences of the amount and reaction temperature of DMPA, catalyst DBTDLamount,-NCO/-OH mole ratio, and the amount and reaction temperature of cappingagent HEMA, hydroquinone inhibitor amount and neutralization and other factors inthe PUA emulsion polymerization process had been studied. Through the studying,optimic reaction conditions and raw materials formula of the emulsion had beenobtained.Through fourier transform infrared spectroscopy (FTIR), the PUA emulsionpolymer structures were characterized. Studied the curing reaction The influences of the reactive diluents TPGDA amount, photoinitiator species and its amount and otherfactors in curing reaction had been been studied. Through the studying, optimic curingreaction conditions and mixture of complex formula had been obtained. Throughthermal synthesis (TG), the thermal stability of the UV-curable PUA coating weretested.The results showed when the DMPA reaction temperature was between80℃and82℃, its dosage amount was between5.5%and6.0%, DBTDL dosage amount was0.4%of DMPA,-NCO/-OH mole ratio was1.55, HEMA reaction temperature was65℃, its dosage amount was between11%and12%, hydroquinone dosage amountwas0.5%of the HEMA amount, neutralization was around100%, TPGDA amountwas9%, photoinitiator was TPO and its amount was4%, light application time wasabout7.0s, the emulsion and film have the best properties.