Curing behavior of tetrafunctional epoxy resin/hyperbranched polymer system

The effects of hyperbranched polymers (HBPs) on the cure behavior of tetrafunctional epoxy resin were investigated using differential scanning calorimetry (DSC) and FT-IR spectroscopy and compared with those of the linear analog. The hydroxyl terminal groups of the HBP initiated the cure reaction through proton donor–acceptor complex. The heat of cure in epoxy/HBP system was higher than that in epoxy/linear polymer system. The activation energy for cure reaction was lower in epoxy/HBP system. When the hydroxyl terminal groups of the HBP were transformed into benzoate groups, the induction time for cure reaction became much longer and the heat of cure was reduced. The isothermal kinetic parameters were obtained from Kamal equation, where the overall reaction order was ca. 1.5. As the cure reaction proceeded, the characteristic peaks of epoxy ring were decreased and H-bonded CO peak was increased. The intensity of the H-bonded CO peak was increased with increasing amount of the HBP.