Effect of diffusion limitation on the kinetics of epoxy‐amine curing reaction

The reaction kinetics and mechanism are prone to affect the properties of the epoxy resins. However, achieving a comprehensive understanding of the curing kinetics presents a challenge, attributed to the multistage exothermic characteristic and the complex viscosity growth regime. This study investigated the kinetics and the rheological characteristics of the curing process of diglycid ether of bisphenol A (DGEBA) and dimethyldicyane (DMDC) with varying content of xylene. The results indicate that diffusion limitation of the epoxy‐amine system is effectively mitigated with increasing xylene content, which results in a higher curing degree and released energy. Subsequently, the density functional theory method was used to investigate the molecular‐level mechanism underlying the epoxy‐amine curing reaction. The interaction between hydroxyl groups and epoxides lowers the energy barrier during the curing, thus there are autocatalytic kinetic characteristics during process. The curing rate during the reaction‐controlled stage is consistent with the characteristics described by the Kamal model, whereas the Kamal model incorporating the diffusion factor can describe the curing rate across the conversion range. This study comprehensively reveals the impact of diffusion on the curing kinetics of epoxy amine reaction, providing valuable perspectives for practical applications in industrial production.