Effect of curing sequence on the photopolymerization and thermal curing kinetics of dimethacrylate/epoxy interpenetrating polymer networks

The isothermal photopolymerization kinetics of a dimethacrylate and the thermal cure of an epoxy/anhydride mixture have been investigated separately and within the 50:50 dimethacrylate/epoxy IPN using differential scanning calorimetry (DSC) and near-infrared spectroscopy (NIR). This combination of cross-linkable resins permits the partial or complete cure of each component independent of each other. DSC studies showed that the conversion of the slower polymerizing component was affected by vitrification, network topology, or phase separation in the IPN. The effect of changing the order of cure of the dimethacrylate or the epoxy within the IPN on the polymerization kinetics of each group was also studied using NIR-the conversion of each species was found to be very dependent on the cure order. Dynamical mechanical thermal analysis was used to investigate the effect of curing sequence on the phase morphology of the IPN and revealed that the 50:50 IPN is two phase when the dimethacrylate is photocured before the cure of the epoxy component but is a single phase when the epoxy is cured first.