A Molecular Dynamics Study on the Influence of Atmosphere on the Characteristics of Thermal Decomposition Products of Cross-Linked Epoxy Resins in Composite Insulators

The degradation of the epoxy resin matrix, triggered by partial discharges within composite insulators, is a prominent phenomenon in decay-like fracture incidents. The decomposition products of epoxy resins could significantly influence the further progression of these incidents. This study establishes crosslinked and non-crosslinked models of epoxy resin molecules, employing molecular dynamics methods to investigate the characteristics of the thermal decomposition products of epoxy resins within composite insulators. The effects of an oxygen atmosphere and a crosslinking network on the properties of pyrolysis small molecule products are also examined. Results demonstrated that the introduction of oxygen notably impacts the thermal decomposition products of small molecules, leading to an increase in CO2 and H2O yields, with no significant effect on CH2O yield. The presence of oxygen also results in an increase in the types and quantities of C2 and C3 products, particularly oxygen-containing compounds. Compared to non-crosslinked epoxy resins, the impact of oxygen on CO2 yield during the thermal decomposition process of crosslinked epoxy resins is relatively minor, but its effect on H2O yield is more substantial. Furthermore, regardless of the presence or absence of oxygen, the types of C2 and C3 products from crosslinked epoxy resins are fewer, implying that the crosslinking network limits intermolecular freedom, thereby resulting in enhanced oxidation reaction capabilities and more stable chemical reaction behaviors.