Effect of the nature of the reactive group on the electron beam curing of model urethane di(meth)acrylates

Abstract In this study, three kinds of model urethane di(meth)acrylates with different radiation-curable groups [one with acryloyloxy (namely H-I-H), one with methacryloyloxy (namely HM-I-HM) and one with half of acryloyloxy and half of methacryloyloxy (namely H-I-HM)] were synthesized. The chemical structures of these products were characterized through attenuated total reflection fourier transformed infrared spectroscopy (ATR-FTIR), proton (1H) nuclear magnetic resonance and elemental analysis. Then, the electron beam (EB) curing process and properties of the synthesized three di(meth)acrylates and a 1:1 mixture of H-I-H and HM-I-HM (namely H-I-H&HM-I-HM) were investigated. ATR-FTIR results showed that the samples containing acryloyloxy groups (H-I-H, H-I-HM, and H-I-H&HM-I-HM) showed a higher polymerization rate and double bond conversion than that containing only methacryloyloxy groups (HM-I-HM). Thermogravimetric analysis indicated that the EB-cured films of H-I-HM and H-I-H&HM-I-HM had relatively good thermal stability, while the film of HM-I-HM with lower double bond conversion and gel content had poor thermal stability. In addition, although acryloyloxy groups have weaker rigidity, benefitting from its improvement of the polymerization degree, the EB-cured coatings with acryloyloxy group had better surface mechanical and basic properties than the coatings containing methacryloyloxy group.