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

Abstract

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 (E_a) 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.