Synthesis and properties of UV curable waterborne hyperbranched aliphatic polyester

The UV curable waterborne hyperbranched polyester (WBHP) consisting of a multi-hydroxy functional aliphatic polyester core, which is endcapped with methacrylic and salt-like groups in different ratios was synthesized. The core is second generation of hyperbranched aliphatic polyester Boltorn(TM) H20 with approximately 16 hydroxyl groups. The effects of different ratios of chemical structure of end groups were studied by evaluating various properties of WBHP such as solubility in water, dynamic viscosity, UV curing rate and final unsaturation conversion. A natural good control over the solubility of the samples was possible by salt-like functionality and raising the temperature. The investigation of solubility characteristics of the modified hyperbranched polyester illustrated that those with higher concentration of salt-like moiety were more soluble while those of having lower salt-like moiety were less soluble. The viscosity of the resin WBHP was reduced rapidly by dilution with water and raising temperature. Water showed a favorable viscosity reduction effect as compared to monomer and its blend with water. The polymerization rate of the resins under UV irradiation in the presence of a photoinitiator showed an increasing trend with higher concentration of methacrylate functionality. (C) 2002 Elsevier Science Ltd. All rights reserved.