Mechanism-informed kinetic modeling of arc-induced ablation and carbon-deposition propensity in gassing polymers

Gassing polymers are widely used in low-voltage switching devices because their arc-induced ablation products promote arc cooling and post-arc dielectric recovery. However, ablation may also generate carbonaceous precursors and residues that deteriorate insulation performance. To link short-timescale atomistic reactions with long-timescale product evolution, this work develops a mechanism-informed chemical-kinetic framework for arc-induced polymer ablation. For PA66, reaction pathways extracted from multi-configuration ReaxFF molecular dynamics are parameterized through database matching, rate-rule estimation, and quantum-chemical calculations, and then incorporated into Reaction Mechanism Generator calculations. A skeletal mechanism with 81 species and 191 reactions is reduced from a detailed mechanism containing 148 species and 967 reactions, while preserving the key product evolution over 1000-5000 K and 1-10 atm. The kinetic analysis shows that H2 is favoured at intermediate temperatures, whereas C2H2 and other unsaturated carbon precursors accumulate during deeper decomposition. A yield-sooting-index-weighted carbon-deposition propensity index, SCSI, is further proposed and applied to PA6, PA66, PA46, and POM. Experiments under three arc currents and three arcing durations show that SCSI correlates inversely with post-arc partial-discharge inception voltage under severe ablation, while the correlation weakens under mild conditions. Cleaning experiments further show that PDIV recovers markedly after removal of retained surface residues, indicating that carbonaceous contamination is a major contributor to severe post-arc dielectric degradation. The proposed framework provides a quantitative link between atomistic ablation chemistry, carbon-deposition propensity, and post-arc dielectric performance.