Synthesis, UV-curing behaviors and general properties of acrylate-urethane resins prepared from castor oil-based polyols

Castor oil-based polyols with high OH values are synthesized through the low odor thiol-ene reaction and then are used for preparing UV-curable acrylate-urethane resins (AUCORs). The structure of the AUCORs is confirmed by H-1 NMR and IR. The AUCORs based resins containing diluents can rapidly form cured films under UV light irradiation in air, with a very high gel ratio of over 95 %. The UV-curing dynamics shows that polymerization rate and final acrylate conversion under the N-2 atmosphere both depend on C(sic)C bond content, but they are reduced under air due to oxygen inhibition effect. All the cured films have good heat stability with an initial decomposition temperature over 300 degrees C. The cured films can display different T-g within the region of 55-85 degrees C depending on the crosslink density tuned by the acrylate/urethane content. The urethane content/diluter can affect some general properties of the coating films, for instance water absorption ability, wettability, hardness and adhesion force. Interestingly, the cured films have a very good light transmittance in the visible light region, as high as that of glass slides.