Influence of nitrogen ion implantation on surface charge accumulation and dissipation of polytetrafluoroethylene

Abstract

To suppress the accumulation of charge on the surface of polytetrafluoroethylene (PTFE) material, radio frequency nitrogen plasma was generated to perform plasma immersion ion implantation (PIII) on the PTFE surface to improve its surface properties. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), water contact angle measurement, surface resistivity measurement and surface potential attenuation measurement were performed on the samples of PTFE material before and after injection to analyze the changes in surface composition and physical properties of PTFE samples after ion implantation treatment. Based on the theory of isothermal surface potential attenuation, the energy levels and density distributions of the surface traps were calculated. The results show that after nitrogen ion implantation, the main change in the chemical composition of the surface of the PTFE material is the destruction and conversion of its own molecular structure, and part of the CF2 structure is transformed into the CF and CF3 structures, resulting in shallower trap levels on the sample surface. The results also show that the water contact angle rose to about 140°, which is about 27° higher than that of the unprocessed sample. The surface resistivity drops to 3×1015 Ω, which is two orders of magnitude lower than that of the unprocessed samples. After 1 min of corona discharge on the surface, the amount of accumulated charge on the surface of the PTFE material processed with nitrogen ion implantation decreased, and the rate of dissipation increased. This is because the lower surface trap level is conducive to surface charge trapping, and the reduction in surface resistivity also promotes the dissipation process of surface charge along the surface. The curve of trap level distribution on the surface of PTFE sample also confirmed this.