Synthesis of hyperbranched polyurethane acrylates and properties of their cured films

The hyperbranched polyurethane acrylates(HBPUA)were prepared by terminal hydroxyl modification of hyperbranched polyester using synthesized 2,4-toluene diisocyanate hydroxypropyl acrylate(TDI·HPA)monomers.The effect of reaction temperature and time on the free-NCO contents of the products were studied.The active monomer kinds and amounts on the properties of UV cured film were investigated by the testings of pendulum hardness,adhesion,toughness and impact strength.The HBPE,HBPUA and its cured film were characterize and analyzed by FT-IR and TG.The result showed that the best synthesis conditions of HBPUA were as followed:n(2,4-TDI)∶ n(HPA)∶ n(HBPE)=6∶ 6∶ 1,rection temperature 70 ℃,reaction time 3 h,catalyst dilaurate tributyltin(DBTDL)amount 0.6%(based on the total mass).The synthesis conditions of TDI · HPA were as followed:reaction tempetature 35 ℃,reaction time 2.5 h,DBTDL amount 0.4%.The mechanical properties and thermal stability of coating films were better using hexanediol diacrylate as active monomer and mass fraction of 20%.