Wettability characteristics of poly(ethylene terephthalate) films treated by atmospheric pressure plasma and ultraviolet excimer light

Two dry processes, atmospheric pressure plasma (APP) exposure and 172 nm ultraviolet (UV) excimer light irradiation, were carried out to enhance the hydrophilic nature of poly(ethylene terephthalate) (PET) film. The wettability change in the PET film surface after the processes were carried out was recorded by the wetting force measurements employing the Wilhelmy method. After the dry processes, drastic decreases in the advancing and receding contact angles of water were observed, especially for the APP exposure. The advancing angle on the treated PET surface was found to increase by rinsing with water or aging in air, whereas the receding one remained almost the same. The hydrophobic recovery diminished more rapidly for the UV-treated film. Surface characterizations of the PET film were performed. We discuss the influence of the dry processes on the physicochemical properties of the PET surface.