Curing kinetics study on interpenetrating polymer networks based on modified hyperbranched polyether/polyurethane

Abstract: Curing kinetics of two kinds of modified hyperbranched polyether/polyurethane interpenetrating polymer networks were investigated by in situ Fourier transform infrared spectroscopy. The results showed that the existence of stearate-terminated hyperbranched polyether (SHPE), without changing the reaction order between hydroxyl-terminated polybutadiene (HTPB) and isophorone diisocyanate (IPDI), still followed a second-order kinetic mechanism, but significantly enhanced its reaction rate; the activation energy was decrease from 28.3 to 16.6 kJ/mol. However, SHPE has no catalytic effect on the reaction between hydroxyl-terminated ethylene oxide tetrahydrofuran copolyether (PET) and IPDI. Main reason for this difference is that the inner and outer structures of SHPE were different. Their different repeating units bring different solubility parameters, resulting in hydroxyl in HTBP and IPDI enrichment near the inner structure of SHPE and HTPB backbone enriched outer layer of SHPE. However, the solubility parameter of PET was close to the inner structure of SHPE, so PET backbone was also in the vicinity of inner structure of SHPE, diluted –OH and IPDI concentration. The results suggested that by molecular structure design, it could gain catalyst for polyurethane.