Effects of power density on surface modification of polytetrafluorethylene by using a homogeneous dielectric barrier discharge at atmospheric air

The surfaces of polytetrafluorethylene (PTFE) films were modified using non-thermal plasma generated by a homogeneous dielectric barrier discharge (DBD) at atmospheric pressure air driven by a μs pulse high-voltage power supply, and the surface properties of the untreated and DBD plasma treated samples were characterized by means of contact angle and surface energy measurement, scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FTIR). Moreover, the changes of surface properties of the PTFE films with discharge power densities were studied, the aging effect after treatment when the treated films were exposed to open air was also investigated, and the modification mechanism was discussed. Results show that after DBD plasma treatment, the surface roughness increases remarkably, and oxygen-containing polar groups are introduced into PTFE surface. The water contact angle decreases with the increase of treatment time and surface energy increases with the increase of treatment time, and both of them reach saturated value at certain treatment time. It is found that, increasing discharge power density can treat the rougher surface and introduce more oxygen-containing polar groups into PTFE surface, so much shorter treatment time is needed to get the same treatment effect by increasing the power density. The aging effect when the treated materials are exposed to open air mainly occurs within the first 6 days, but the value of water contact angle is still far lower than that of the untreated materials even after longer storage.