A Spectroscopic Study on Argon-Ammonia Water Gaseous Plasma Super-hydrophilizing Polytetrafluoroethylene

Abstract

In this study, optical emission spectroscopy was used to investigate the advantages of using NH₃ and water with Ar gas plasma. To compare the plasma characteristics of N₂, NH₃, and Ar plasma, Ar/H₂O vapor and Ar/NH₃-H₂O were investigated. The results show that RF-ICP is non-thermal plasma with T_e higher than T_g, especially in air, N₂, and Ar/NH₃-H₂O plasma with T_e of about 32,500 K (ca. 2.5 eV), T_ν of about 7000 K (ca. 0.5 eV), T_r of about 1000 K, and T_g of about 320 K. In the Ar/NH₃-H₂O plasma, similar to the Ar/H₂O plasma, water dissociated readily to form OH and H I radicals, and the high H I concentration makes NH₃ suppressed the dissociation reaction and may proposed ionization reaction to form NH₃⁺ ion that minimum pressure change. In the PTFE surface treatment with Ar/NH₃-H₂O plasma, the suppression of NH₃ dissociation may be caused by the increased formation of NH₃⁺, which is the main factor in promoting defluorination. The high OH radical concentration may increase the number of polar groups grafted to the polymer surface, decreasing the WCA and making the PTFE surface super hydrophilic after treatment.