Comparision of the properties of UV-cured polyurethane acrylates containing different diisocyanates and low molecular weight diols

UV-curable polyurethane acrylate prepolymers were prepared from diisocyanates [isophorone diisocyanate (IPDI), 2,4-toluene diisocyanate (TDI), or 4,4′-dicyclohexylmethane diisocyanate (H12MDI)], diols [ethylene glycol (EG), 1,4-butane diol (BD), or 1,6-hexane diol (HD)], polypropylene glycol as a polyol. UV-curable mixtures were formulated from the prepolymer (90 wt%), reactive diluent monomer trimethylol propane triacrylate (10 wt%), and photoinitiator 1-hydroxycyclohexyl ketone (3 wt% based on prepolymer/diluent). The effects of different diisocyanates/low molecular weigh diol on the dynamic mechanical thermal properties and elastic recovery of UV-cured polyurethane acrylate films were examined. The tensile storage modulus increased a little in the order of EG > BD > HD at the same diisocyanate. Two loss modulus peaks for all samples are observed owing to the glass transition of soft segments (Tgs) and the glass transition temperature of hard segments (Tgh). For the same diisocyanate, T gs decreased, however, Tgh increased, in the order of HD > BD > EG, The elastic recovery also increased in the order of HD > BD > EG at the same diisocyanate. In case of same diols, Tgh increased in the order of H12MDI > TDI > IPDI significantly. The ultimate elongation and elastic recovery increased in the order of TDI > IPDI > H12MDI at the same diol.