Synthesis,Structure And Properties Of UV-curable Linear/Hyperbranched Polyurethane Acrylate

In the era of rapid development,people s awareness of environmental protection is gradually increasing.Countries all over the world are aimed at studying new environmental friendly coatings.UV-curable polyurethane acrylate coating has such advantages as low VOC emission,energy saving,fast curing speed,high production efficiency and the cured film has excellent abrasion resistance,flexibility and chemical resistance.This paper is aimed at synthesizing UV curable polyurethane acrylate and UV curable hyperbranched polyurethane acrylate.Based on polydiethylene glycol-2000 as soft segments,different glycol chain extenders and isophorone diisocyanate(IPDI)as hard segments,2-Hydroxyethyl acrylate(HEA)as blocking agent,a series of UV-curable polyurethanes acrylate were compounded using prepolymer method.The relative activities of different glycol chain extenders as chain extenders were analyzed;the structure of UV-curable polyurethane was characterized by infrared spectral,and the influences of different glycol chain extenders on the mechanical performance,heat resistance performance and using performance of cured film were studied.The results showed that under the temperature 80℃,the reaction speed of ethylene glycol and phenyl isocyanate(PI)is the fastest,the speed of 1,2-propylene diatomic alcohol and PI is the slowest;1,4-cyclohexane dimethanol(CHDM)as chain extender of PU has the best mechanical properties and heat resistance.In this paper,pentaerythritol(PE),IPDI were as raw materials to synthesize polyhydroxy hyperbranched precursor(HBPU-0).The structure of products were tested by infrared spectroscopy(FT-IR)and nuclear magnetic resonance(1H NMR),which is consistent with the structure of the imagination.When the single NCO-terminated polyurethane prepolymer was grafted on HBPU-0,a series of UV curable hyperbranched polyurethane acrylate with different content of grafting degree were obtained,comparing with the same molecular weight linear polyurethane acrylate on the viscosity,mechanical performance,heat resistance performance and using performance of cured film.The results indicated that the viscosity of HBPUA resin was much lower,and mechanical performance,heat resistance performance and using performance of it s cured film was superior to the linear polyurethane.Among them,the mechanical properties of UV curable hyperbranched polyurethane film were the best when the modification degree of HBPU-0 was 83.3%,and the tensile strength reached 4.89Mpa.Take IPDI,JZ-156,2,2-dimethylol propionic acid(DMPA)and HEA as materials to synthesize polyurethane prepolymer(PU2)by two-step method,and a series of UV-curable waterborne hyperbranched polyurethane acrylate dispersions were prepared by grafting PU2 and IPDI/HEA(PU3)on HBPU-0 with different proportions.The structure of the product was characterized by IR,and the properties of the cured film were studied.The effects of the number of polyurethane prepolymer and the number of IPDI/HEA segments on the mechanical properties,heat resistance,viscosity and particle size of the cured films were investigated.The results showed that with the increase of the number of PU3 segments,the tensile strength and heat resistance of the cured film increase,the particle size of the emulsion increases gradually,and the tensile strength is up to 15.63Mpa.