The surface modification of poly(tetrafluoroethylene) film using dielectric barrier discharge of intermittent pulse voltage

The surface of a poly(tetrafluoroethylene) (PTFE) film was modified using a dielectric barrier (filament) discharge in air at atmospheric pressure. The dielectric barrier discharge was produced by intermittent one-cycle sinusoidal (OCS) voltage with a duration of 10 mu s and a peak voltage of 8-13 kV. The frequency was 5-100 kHz. The electrodes covered with silicon rubber were rotated at 240 rev./min for the uniform modification of the film surface. Immediately after the modification, the contact angle of a water drop was measured with a contact angle meter. The intermittent discharge at a duty cycle of 20% required a process time of 20 s for the whole surface to experience the discharge. The minimum contact angle of a water drop on the modified surface was approximately 70 degrees. The quiet time of a certain length was necessary to minimize the contact angle, and consequently, the stationary waveform was inappropriate for the modification. The intermittent pulsed voltage was advantageous for long-term operation of the PTFE modification, because overheating of the dielectric material can be avoided. (C) 2000 Elsevier Science S.A. All rights reserved.