Promotion of Epoxy Resin Surface Electrical Insulation Performance and Its Stability by Atmospheric Fluorocarbon Dielectric Barrier Discharge

Abstract

This study investigates the promotion of epoxy resin (ER) surface electrical insulation and its stability by atmospheric fluorocarbon dielectric barrier discharge (DBD) plasma. Surface physicochemical and electrical properties of untreated and plasma treated samples are evaluated by scanning electron microscopy, X-ray photoelectron spectroscopy, surface and volume resistivity, surface charge accumulation, dissipation measurements, and flashover tests. Analysis shows that dusty-like fluorocarbon granules formed in plasma phase are deposited on ER samples and the concentration of fluorine groups is increased after plasma treatment. The surface withstand strength of epoxy resin in vacuum can be promoted up to 50%. Surface resistivity decreases by two orders of magnitude with treatment time while volume resistivity reduces slightly. The surface charge accumulation on treated ER samples is prohibited and the maximum surface charge density decreases from 77.84 to 1.42 pC/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The surface charge dissipation is accelerated with the central energy levels reducing to below 0.9eV and the density of electron traps increases from ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sup> to ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sup> eV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . Furthermore, the stability of surface flashover strength is tested. It is found that promotion of surface flashover strength of treated ER sample is stable after being kept in ambient air for a month. The physicochemical changes caused by plasma treatment prevents electrons from transferring to the surface which leads to a better surface insulation performance.