Improvement of surface insulating performance for polytetrafluoroethylene film by atmospheric pressure plasma deposition

Abstract

The surface flashover phenomenon across vacuum-dielectric interface severely limits the service life and operational reliability of high voltage electrical equipment. The surface modification by atmospheric pressure plasma treatment is a promising method to improve the surface insulating performance of polymers. In order to explore the effect mechanism of plasma processing on the vacuum flashover characteristics of polymer materials, the atmospheric pressure plasma deposition was used to treat polytetrafluoroethylene (PTFE) film. The surface parameters under different processing conditions, such as surface chemical composition, surface resistivity, surface charge decay and trap distribution, were tested and analyzed. The space charge distribution of PTFE and the flashover voltage in vacuum were measured. The results show that Si-O-Si and Si-OH groups are introduced on the surface of PTFE, and the characteristic peaks of PTFE are gradually weakened with the increase of processing time. The surface trap density increases and more traps with lower energy level arise with longer processing time. The plasma deposition changes the space charge distribution in PTFE body, and leads to positive charge accumulation inside the sample. The flashover field strength respectively increases by 15% and 70% in direct current (DC) voltage and microsecond pulse voltage afrter plasma deposition. The rapid dissipation of surface charge is the main reason for pulse flashover voltage enhancement, while the increase of surface leakage current due to lower surface resistivity and space charge accumulation in PTFE body make the DC flashover voltage reach the saturation point. Therefore the surface insulating and body performance of polymer materials after plasma modification processing should be considered comprehensively based on different applications.

Superior Surface-Insulated Polymers with Low Leakage Current Enabled by Tailored Coatings Deposited with Colliding Plasma Jets

“…If no new electron is injected, then the surface potential will decrease to zero. However, many experimental results show that after a long time without new electron injection, the surface potential still has a certain distance from the ground potential (the value may be 10–50% of the initial potential ,, ). This means that other binding factors enable the surface to capture certain electron and store it for a long time, which many scholars call “deep traps”. ,− Previous studies have shown that electron needs certain energy to cross the barriers of surface bumps and pits, so a rough surface can serve as a macroscopic barrier to capture charge .…”