Study On The Generation Of Atmospheric Pressure Gas-liquid Plasma And The Surface Modification Of Polytetrafluoroethylene Films

Polytetrafluoroethylene（PTFE）has been widely used in various fields of industry because of its excellent mechanical properties,light weight and low cost.But PTFE is also unsuitable to use in many fields,because of its low surface energy,poor surface wettability,hydrophilicity and dyability.The atmospheric pressure low-temperature plasma treatment is a surface treatment technology of dry and low pollution,which only change the surface properties of 10nm depth of the materials being processed,and not change the original characteristics of the materials.So,it has great market and application prospect,and it is a hot spot of the research at home and abroad.In this paper,the surface treatment of PTFE thin films by atmospheric pressure single gas and gas-liquid dielectric barrier discharge（DBD）plasma was carried out.The results of the study include the following three aspects.1.The experimental researches of atmospheric single air DBD plasma and different solution gas-liquid two-phase DBD plasma are carried out,and their discharge characteristics are compared and analyzed.The results show that when the discharge gap and discharge frequency are the same,for the beginning discharge voltage and the stable discharge voltage,the discharge voltage of the atmospheric pressure single air discharge is highest,the discharge voltage of air/deionized water gas-liquid two-phase DBD is lower,and the discharge voltage of the air/acetone/deionized water two-phase DBD is the lowest.2.The surface modification of PTFE films are studied using single air DBD plasma and air/deionized water gas-liquid two-phase DBD plasma at atmospheric pressure.The surface water contact angle measurement,the scanning electron microscopy（SEM）,the fourier transform infrared attenuated total reflection（FTIR-ATR）and X-ray photoelectron spectroscopy（XPS）were used to characterize and analyze the modification effects of PTFE films before and after plasma treatment.The results show that the surface water contact angle of PTFE thin films treated by the single air plasma and air/deionized water gas-liquid plasma are all reduced from about 100^o to about 70^o.The PTFE thin films changed from hydrophobic to hydrophilic,and with the increase of the treatment time,the surface water contact angle gradually tends to saturation.Furthermore,it can be known by the analysis of SEM for the PTFE thin films after plasma treatment that the surface of the PTFE thin films appears these phenomena,such as adhesion,melt-out,etching,etc.They increase the surface roughness of the PTFE thin films,thus to improving the surface hydrophilicity of the PTFE thin films.Thirdly,the results of XPS and FTIR-ATR show that after the single air DBD plasma treatment,the content of oxygen-containing functional groups introduced from 0.95%to2.27%and the content of nitrogen-containing functional groups is 0.39%.And after the gas-liquid two-phase DBD plasma treatment,the oxygen-containing groups introduced to2.47%and 0.47%is the nitrogen-containing groups.So the content of oxygen-containing and nitrogen-containing functional groups on the PTFE surface is higher after the air/deionized water gas-liquid two phase plasma treatment than the single air plasma treatment at atmospheric pressure.3.The surface of PTFE films was respectively treated by air/O2 DBD plasma and air/O2/deionized water DBD plasma.The results show that the surface hydrophilicity of the PTFE films after treated by two kinds of plasma is improved.But,different from the research results of the second part,the content of oxygen-containing and nitrogen-containing functional groups introduced in the surface of PTFE thin film after air/O₂/deionized water plasma treatment is 0.14%and 0.05%lower than that after air/O₂ plasma treatment.And after adding O₂,the content of oxygen-containing functional groups introduced in the surface of PTFE film after plasma treatment is higher than that without adding O₂.