UV curable polyurethane-based microspheres

Radiation curable polyurethane-based microspheres were prepared by modifyin g conventional procedures for preparing anionic polyurethane dispersions. V inyl groups were introduced to the side chains and the ends of the polyuret hane main chains. Photoinitiators and multifunctional acrylate oligomers we re incorporated into each microsphere. The curing behavior of the films obt ained from these microspheres under UV were studied. The MEK resistance of UV cured films without multifunctional acrylate oligomers was raised when t he content of vinyl groups is above a certain threshold value. The effect o f the incorporation of multifunctional acrylates oligomers on MEK resistanc e was observed. This effect was remarkable at low UV irradiation intensity. The curing behavior of the films was followed by real time FT-IR spectrosc opy. The accelerating effect of the incorporation of multifunctional acryla tes became striking particularly at the early stage of curing process. Mult ifunctional acrylates were found to be effective in raising the extent of t he conversion of the double bonds. The curing behavior under UV irradiation was compared with that under EB irradiation. (C) 1999 Elsevier Science B.V . All rights reserved.