Surface modification of polyethylene terephthalate films using dielectric barrier discharge driven by repetitive nanosecond pulses

Surface treatment of polyethylene terephthalate(PET) films for improving the hydrophilicity using dielectric barrier discharge(DBD) excited by unipolar nanosecond pulses is presented. Homogeneous and filamentary discharges are obtained under certain experimental conditions and then used to modify the surface of PET films. The properties of PET films before and after treatment are characterized with water contact angle measurement, atomic force microscope and X-ray photoelectron spectroscope. The experimental results show that static water contact angles decrease evidently after DBD plasma treatment and the observed contact angle changes from 78° for the untreated samples to 25° after treatment. However, the decrease of contact angles is not continuous and it will reach a saturation state after certain treatment time. The improvement of surface hydrophilicity can be attributed to the enhancement of surface roughness and the introduction of oxygen-containing polar functional groups. In contrast with the filamentary DBD treatment, the homogenous DBD is more effective in PET surface treatment.