Influence of Oxygen Content on Argon/Oxygen Dielectric Barrier Discharge Plasma Treatment of Polyethylene Terephthalate Film

In this paper, the dielectric barrier discharge (DBD) is generated in argon/oxygen gas mixtures with various of oxygen content and is employed to treat Polyethylene terephthalate (PET) surface. The effects of oxygen content in the argon/oxygen feeding gas on the properties of DBD and surface properties of PET films are investigated by means of electrical measurements, optical diagnostics, and the surface characteristics analysis. It is shown that after all DBD plasma treatments, the water contact angles on the surface decrease and oxygen containing polar groups on the surface increase. The improvement of hydrophobicity on PET surface is found to be significantly influenced by the addition oxygen content. Adding a small content of oxygen to feeding gas can result in a more efficient treatment, while the discharge induces less effective treatments at relative large oxygen content. There exists an optimum oxygen content for the hydrophilicity improvement on the PET surface, and the lowest contact angle and the highest incorporation of oxygen-containing groups are obtained after argon/oxygen DBD treatment with 0.3% addition of oxygen, which is in agree with the optimum oxygen content for atomic oxygen generation in the discharge regime. The results can be explained by the influences of oxygen addition on the generation and quenching mechanisms of corresponding atomic oxygen radicals in the DBD plasma, which suggests that the efficiency of DBD plasma surface modification can be increased and controlled by a way of adding an appropriate ratio of oxygen into the carrier gas.