Urethane acrylate resins based on partially modified aliphatic hyperbranched polyesters (HBP) were synthesized. HBP of the second and the third pseudo-generation were synthesized from 2,2-bis(hydroxymethyl)propionic acid and di-trimethylol propane. The modification of 60% of the OH end-groups was carried out with isononanoic acid. Urethane acrylates with different degrees of acrylation were obtained by reaction of partially modified HBP and different amounts of acrylate-isocyanate adduct (NCO), which had been previously obtained by reaction of equimolar amounts of isophorone diisocyanate and 2-hydroxyethyl acrylate. The synthesized samples were characterized by FT-IR, H-1 and C-13 NMR spectroscopy and GPC. The rheological properties of uncured samples and the mechanical and thermal properties of UV cured urethane acrylates diluted with 20 wt.% hexanediol diacrylate were examined. The modification of the OH end-groups with isononanoic acid caused a rapid decrease in the viscosity of the HBPs. The examined properties of the urethane acrylates mainly depended on the degree of acrylation. (c) 2006 Elsevier B.V. All rights reserved.