Photopolymerization of waterborne polyurethane acrylate dispersions based on hyperbranched aliphatic polyester and properties of the cured films

摘要

A series of novel water-borne hyperbranched polyurethane acrylates for aqueous dispersions (WHPUD) based on hydroxy-func-tionalized hyperbranched aliphatic polyester Boltorn~(?) H20 were investigated and used as UV curable oligomers.The aqueous dispersions were electrostatically stabilized with carboxyl groups incorporated into their structures,which were neutralized by trie thy lamine.The photo-polymerization kinetics of these WHPUDs was studied with respect to polymerization rates and unsatu-ration conversions in the presence of a photoinitiator using differential scanning calorimetry.The polymerization rates of the resins under UV irradiation and the gel contents in the cured films showed an increasing trend with higher concentration of acrylate functionality,which is in favor of the theory of radical chain polymerization.The mechanical and thermal behaviors of UV cured films of aqueous dispersions were evaluated by tensile testing and dynamic mechanical thermal analysis (DMTA).The results of DMTA investigations indicated that the glass transition temperature shifted to higher temperature as the content of the hard segment consisting of IPDI-HEA increased.Moreover,the storage modulus and pendulum hardness also increased with increasing the hard segment content.As the degree of neutralization increased,the T_g and tensile strength decreased,whereas,the elongation at break increased.