Curing Kinetics of Biobased Resins Based on Soybean Oil and Isosorbide Catalyzed by Al(OTf)3

The curing kinetics of a biobased epoxy, formulated based on epoxidized soybean oil (ESO) and isosorbide (ISO), catalyzed by aluminum triflate, Al(OTf)3, were investigated using differential scanning calorimetry (DSC). The resins were synthesized with catalyst concentrations at 0.05, 0.07, and 0.10 mol% upon two different ratios of ESO to ISO (1:1 and 1:2). The exothermic peak associated with the epoxy ring opening was observed at temperatures ranging from 80°C to 115°C, influenced by both the heating rate and the amount of catalyst. To analyze the curing kinetics and determine the activation energy (Ea) as well as the autocatalytic parameters, both model-free isoconversional and model-based methods were employed. The kinetic mechanism was found to be significantly affected by the catalyst and ISO contents. For compounds with lower concentrations of aluminum triflate, Al(OTf)3, and ISO, the model-based methods (Bna and Cn) yielded fits with deviations of less than 3%, confirming the autocatalytic nature of the reactions. In contrast, higher concentrations of aluminum triflate, Al(OTf)3, and ISO led to complex reaction mechanisms, resulting in deviations of approximately 30% and rendering the model-free Friedman and numerical optimization methods ineffective.