Surface Treatment of Polyethylene Terephthalate Films Using a Microsecond Pulse Homogeneous Dielectric Barrier Discharges in Atmospheric Air

Drived by a μs pulse high-voltage power supply, a homogeneous DBD in atmospheric air is generated between two plane-parallel electrodes, with PTFE plates as dielectric barriers. The discharge generated shows homogeneous discharge characteristics. The light emission is radially homogeneous and covers the entire surface of the electrodes, and a single current pulse with duration of about 1 s and amplitude of less than 1 A appears in each voltage pulse. The homogeneous DBD is used to treat the polyethylene terephthalate (PET) films to improve their surface hydrophilicity, and as the main operating parameters, the effects of discharge power density of the homogeneous DBD on the surface treatment are also studied. The surface properties of PET films before and after treatments are studied using the following: 1) contact angle and surface energy measurement; 2) attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR); 3) X-ray photoelectron spectroscopy (XPS); and 4) scanning electron microscopy (SEM). The results of contact angle and surface energy measurements reveal that the homogeneous DBD treatment can improve the surface hydrophilicity of PET films, as it can induce a remarkable decrease in water contact and a remarkable increase in surface energy. The results of SEM, XPS, and FTIR shows that improvement of the hydrophilicity due to both the introduction of oxygen-containing polar groups onto the surface and the etching of the surface. It is found that increasing discharge power density of homogeneous DBD can induce more effective treatment of PET films, and less treatment time is needed to achieve the same level of surface treatment by increasing the discharge power density.