Molecular Dynamics Study on the Enhancement of Electrothermal Stability of HTV SR by Different Functional Groups of POSS

The occurrence of electrothermal decomposition in high-temperature vulcanized silicone rubber (HTV SR) significantly compromises the insulation performance of composite insulators. The effective modulation of its electrothermal stability is achieved by incorporating organic nanofillers into the HTV SR. Currently, introducing polyhedral oligomeric silsesquioxane (POSS) as a doping filler into HTV SR represents a key direction in the modification of organosilicon materials. However, traditional experimental methods have difficulty explaining the mechanism through the microscopic perspective, by which POSS enhances the electrothermal stability of HTV SR. Therefore, this article constructs three models: a pure HTV SR model and two composite models with octavinyl-POSS and octaphenyl-POSS dopants in HTV SR. First, based on molecular dynamics simulations, the enhanced key properties of different composite models are analyzed. Then, based on the reactive force field simulation, the micro-regulation role of POSS in enhancing the electrothermal stability of HTV SR was investigated. The results indicate that the introduction of POSS inhibits the breaking of chemical bonds in HTV SR molecules, reducing the formation of decomposition products such as CH4 and H2, with maximum decreases of 28.3% and 13.3%, respectively. Simultaneously, POSS also promotes crosslinking carbonization between the molecular chains of HTV SR, alleviating the damage caused by the decomposition of the material. Among them, octaphenyl-POSS has a better overall enhancement effect, and octavinyl-POSS has a better compatibility with the HTV SR system, which provides a reference basis for the selection of POSS dopant materials suitable for the modification of HTV SR.