UV-curable Epoxy Systems containing Hyperbranched Polymers: kinetics investigation by p-DSC and real-time FT-IR experiments

The effect of the presence of an hyperbranched OH-functionalized polymer (HBP) on the kinetics of cationic photopolymerization of an epoxy system was investigated employing two complementary techniques, photo-DSC and real-time FT-IR spectroscopy. Lower rates of cross-linking reactions and higher conversion degrees were obtained in photo-DSC experiments with respect to real time FT-IR spectroscopy. A limited amount (10% wt.) of HBP influenced to a certain extent the cure kinetics of the epoxy resin followed by RT-IR; a final conversion of epoxy groups equal to 100% was achieved by increasing the content up to 20% wt.. The addition of 10% wt. of HBP leaves almost unchanged the cure kinetics of the CE resin studied by p-DSC. By increasing the content of HBP, a slightly lower reaction rate is observed at lower reaction times. The presence of the HBP determined a continuous decrease of the Tg of the UV-cured epoxy resin but only modest reductions in its thermo-oxidative stability.