Revealing the pyrolysis mechanisms of cured epoxy resin in waste thermoset composites by using experiments and ReaxFF-MD simulation

MX Xu and YY Lu and WW Chen and YC Wu and Q Lu and Q Lu, POLYMER DEGRADATION AND STABILITY, 241, 111578 (2025).

DOI: 10.1016/j.polymdegradstab.2025.111578

The disposal of waste epoxy resin-based composites is a significant global environmental challenge, with the decomposition of the epoxy resin matrix being the bottleneck. Pyrolysis is regarded as one of the most promising technologies for recycling these composites, while complex secondary reactions limit the yields of high-value pyrolysis products. In this study, the pyrolysis mechanisms of cured epoxy resin were investigated through the combination of thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR), rapid pyrolysis experiments, and reactive force field molecular dynamics (ReaxFF-MD) simulations. The results revealed that the depolymerization of cured epoxy resin was initiated by the cleavage of C-O bonds, leading to the formation of heavy pyrolysis oil. Secondary cleavage of C-C bonds in heavy oil subsequently generated light oil, accompanied by the migration of oxygen atoms into the gas phase. Meanwhile, hydrogen radicals, methyl radicals, and hydroxyl groups were produced, promoting the formation of pyrolysis gas via intermolecular and intramolecular dehydrogenation, methyl hydrogenation, and the dissociation of C-C-O or C-C=O structures, respectively. Furthermore, aromatic-rich heavy pyrolysis oil containing crosslinked C-N bonds underwent hydrogenation to generate cycloalkanes, initiating the formation of nascent carbon nuclei, which subsequently transformed into thermodynamically sTable 6-M rings through dehydrogenation and reorganization reactions, ultimately yielding pyrolysis char with an ordered and graphitized morphology. These findings provide theoretical insights for optimizing and advancing the pyrolysis recovery of waste thermoset composites.

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