Impact of SF6 Decomposition Products on Epoxy Resin Chemical Stability and Doping-nano-Al2O3-based Enhancement Using the ReaxFF-MD Method

Chemically active by-products formed by corona discharge in SF 6 gas are prone to damaging the exposed epoxy resin, or even leading to an entire insulation failure of the operational GIS/GIL power equipment. In this proposed research, reactive force field molecular dynamic simulation methodology is applied to investigate the chemical reaction kinetics of epoxy polymer under the impact of highly energetic particles (F, S, SOF, SF, OH and O) so as to explain the degradation mechanism. Among all cases, SF particle-impacted epoxy resin suffers the most serious surface erosion with the lowest remnant mass of 9% and deepest damage penetration of 32.6Å, to which the S particle-caused damage showed similar results. Due to high reactivity of the S atom, it can merge into the epoxy molecules to promote long chain breaking, causing a six-membered ring opening and further dissociation of short carbon chains, which makes the epoxy resin molecules undergo faster spontaneous dissociation with increased temperatures. The changes of small molecular gas products, such as CO 2 , H 2 O and CH 2 O, as well as that of the characteristic products, such as HF, CS 2 , SO and H 2 S, are also evaluated under the impact of different particles. The presented research indicates that enhancing the resistance strength of epoxy polymer against S and SF particles' corrosion is the key approach to improving chemical stability in the SF 6 environment. Further studies were implemented to optimize the concentration and diameter of nano-Al 2 O 3 doped in the composites. According to this paper, aluminum nanoparticle with a diameter of 1nm could significantly reduce the erosion caused by SF and S particles. The micro-scale mechanism lies primarily within two aspects: the nanoparticles improve the surface heat transfer efficiency as to reduce temperature rise, and also provide an effective protection area by balancing distribution and self-exposing, which finally slows down the pyrolysis process of epoxy resin, as well as the reaction intensity with the incident particles.