Curing Behavior and Structure Reactivity‐Property Relationships in Epoxidized Linseed Oil Thermosets Crosslinked With Biobased Eutectic Hardeners

Three eutectic hardeners citric acid/ethyl lactate (CAEL), tartaric acid/ethyl lactate (TAEL) and malic acid/ethyl lactate (MAEL) were used to study the crosslinking behavior of epoxidized linseed oil (ELO), resulting in ELO/CAEL, ELO/TAEL and ELO/MAEL thermoset polymer. This study was performed to investigate the effect of the molecular structure of citric acid, tartaric acid, and malic acid on polymerization and crosslinking kinetics. Nonisothermal DSC was used to determine effective active energy and pre‐exponential factors, while DMTA provided insight into the resulting thermomechanical properties. Among the systems, ELO/TAEL showed the lowest activation energy and the most efficient curing profile. TAEL formed the more rigid polymeric network with the highest glass transition temperature. In contrast, ELO/MAEL showed higher reaction rates, primarily due to its higher A α values. However, its lower hydroxyl content resulted in a less crosslinked network, as reflected by its lower glass transition temperature. In the ELO/CAEL system, the higher functionality and sterically hindered structure of CA displayed intermediate behavior. These results demonstrate that the number of hydroxyl and carboxylic groups determines the kinetic and macroscopic properties of ELO‐based thermosets. The findings provide insights into structure reactivity for designing the next generation of biobased thermosetting materials for flooring applications.