Bio‐Based Amino Acid Curing Additives: Mechanistic and Kinetic Effects in Epoxidized Soybean Oil Epoxy Thermosets

ABSTRACT In this study, the curing and thermal degradation kinetics of epoxidized soybean oil (ESO) were investigated using L‐aspartic acid (AA) and DL‐malic acid (MA)—two bio‐derived dicarboxylic acids—as curing agents, in the presence of aluminium triflate (AT) as catalyst (0.5 and 1 wt%). Reactions were monitored by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and coupled TGA–FTIR techniques, and data were evaluated by model‐free and model‐fitting kinetic approaches to elucidate cure behavior, degradation mechanisms, and volatile decomposition products. Both ESO/AA and ESO/MA systems exhibited comparable total curing enthalpies, with AA formulations showing consistently higher activation energies, attributed to the zwitterionic nature of the amino acid. Despite the higher energetic demand, ESO/AA compositions demonstrated superior thermal stability, with onset degradation temperatures above 200°C and degradation activation energies (E a ) exceeding 700 kJ·mol −1 . Model fitting revealed a multi‐step degradation mechanism, best described by Avrami–Erofeev (An) and Šesták–Berggren (SB) models, indicating nucleation‐dominated behavior with secondary surface contraction. TGA–FTIR analysis confirmed water, carbon dioxide, and carbon monoxide as primary gaseous products. These findings highlight the strong potential of amino acid‐cured ESO systems as thermally robust, non‐toxic, and renewable alternatives to conventional epoxy resins in applications such as adhesives and composites.