UV-curable hyperbranched urethane acrylate oligomers containing soybean fatty acids
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Urethane acrylate resins based on partially modified aliphatic hyperbranched polyesters (HBP) have been synthesized. HBP of the second and the third generation were synthesized from 2,2-bis(hydroxymethyl)propionic acid and di-trimethylol propane. The modification of certain amount of OH end-groups was carried out with soybean fatty acids. The urethane acrylates with different degrees of acrylation have been obtained by reaction of partially modified HBP and different amounts of NCO adduct 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 and GPC. The theological properties of uncured samples and mechanical and thermal properties of UV cured urethane acrylates diluted with 20 wt.% hexanediol diacrylate were examined. The modification of OH end-groups with soybean fatty acids causes a rapid decrease in viscosity of HBP. The examined properties of ...urethane acrylates depend on the degree of acrylation. After irradiating, the additional cross-linking, which is caused by reaction of double bonds from unsaturated fatty acids, has also important effect on the properties of cured samples. (C) 2004 Published by Elsevier B.V.