Improved flashover performance and tracking resistance of silicone rubber by direct fluorination

Abstract

Silicone rubber (SIR) samples are fluorinated using a F2/N2 mixture at different temperatures. Physicochemical characteristics are analyzed by attenuated total reflection infrared spectroscopy, X‐ray photoelectron spectroscopy, and scanning electron microscopy. Basic properties of the fluorinated surface layers are investigated, and the intrinsic alternating current (AC) flashover performance and tracking resistance of the surface fluorinated samples are evaluated. The flashover test results indicate that the fluorination leads to an improvement in AC flashover performance of the SIR material, as a result of the competition between the favorable effect of the increase in surface conduction and the adverse effect of a likely increase in surface layer permittivity. The increase in AC flashover voltage is associated with the voltage‐increasing mode of the flashover test. The flashover test results also show an improved tracking resistance of the SIR material by the fluorination, and the improvement is especially significant for the fluorinated surface layer that has less cleavage of SiC bonds or a good compactness as well as a large thickness. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48556.

Arc Tracking Control in Insulation Systems for Aeronautic Applications: Challenges, Opportunities, and Research Needs

“…Insulation materials are subjected to mechanical, electrical and environmental stresses [25], as well as electrostatic discharges, which may generate cracks in wiring insulation materials [26]. In particular, environmental stresses such as ultraviolet radiation from sunlight, moisture, contaminants and pollution such as ozone or acid rain [27] and aged polymeric insulation materials [28] could degrade the material due to surface tracking [29] and erosion [30].…”

“…It is known that surface treatments may increase the arc tracking resistance of polymeric materials. In [25] it is proved that by fluorinating silicon rubber (SiR) samples by means of an F 2 /N 2 mixture, flashover tests show an improvement of the tracking resistance. SiR insulation systems are additivated with different filler materials that are used to increase the hydrophobicity.…”

“…Hydrophobicity tends to delay leakage current development [59]. However, due to the presence of moisture and contamination, the outer layer of the insulation can change from hydrophobic to hydrophilic [25]. Since this wet layer is conductive, a leakage current is generated in this new conductive layer.…”

“…It was shown that low-energy corona discharges and UV radiation can break C-H and Si-CH3 bonds of SiR insulation, thus converting to hydrophilic the initially hydrophobic polymer surface [25]. Once contaminated or oxidized, SiR cannot easily recover hydrophobicity.…”

Monitoring of Dry Bands and Discharge Activities at the Surface of Textured Insulators with AC Clean Fog Test Conditions

“…Many studies were carried out regarding the performances and the optimization of polymeric insulators. Material characteristics as well as geometry and profiles were investigated [5,6]. However, like all polymers, they are vulnerable to long-term degradation due to aging and weathering [7][8][9][10].…”