Simultaneous cationic polymerization and esterification of epoxy/anhydride system in the presence of polyoxometalate catalyst

Polyoxometalate exhibits high catalytic performance for the simultaneous cationic polymerization and esterification of epoxy resin when anhydride is introduced as a co-hardener. The selective catalysis effect of polyoxometalate and the reaction mechanism was studied by differential scanning calorimetry (DSC), mid-infrared spectroscopy (MIR), near-infrared spectroscopy (NIR) and generalized two-dimensional correlation analysis. The cationic polymerization is the dominating reaction in neat epoxy systems. Increasing the amount of polyoxometalate and the polarity of the diluents fastens the curing rate of epoxy resin. Esterification was found to be the preferred reaction once anhydride was employed. When polyoxometalate was blocked by amine to form salt, it performs as an excellent catalyst for esterification in epoxy–anhydride systems. The epoxy materials catalyzed by polyoxometalate show quite good performance compared with ordinary epoxy resins. Moreover, thermal degradation analysis (TGA) shows that polyoxometalate could significantly decrease the thermal degradation temperatures of cured epoxy resins.