Hydrophilicity enhancement of polymers film surfaces by dielectric barrier discharge

The surfaces of polymethylmetacrylate (PMMA) and polycarbonate (PC) films were modified by homogeneous, dielectric barrier discharge (DBD) plasma at medium pressure air. The impacts of the surface modification conditions, including the power densities, modification time, and exposure time in air, on properties of the films were studied. The surface hydrophilicity of the two types of films, before and after the surface modifications, were evaluated via the contact angle measurement, surface energy evaluation and with attenuated total reflectance Fourier transform infraed spectroscopy (ATR-FTIR). The results show that the surface modification significantly affects the hydrophilicity of all the films. For example, as the modification time increases, the contact angle decreases, the surface energy increases, and the above two parameters saturate at a critical modification time; a combination of an increase power density and a much shorter modification time leads to the same results. Interesting finding is that though aging effect was observed, after 14 days of exposure to air, their water contact angles were still much smaller than those of the control samples.