HYDROPHILIC BEHAVIOR OF POLYMER FILMS TREATED BY ATMOSPHERIC PRESSURE PLASMA

Abstract

Experiment on the surface characteristics of polymer films (PC, PET, EVA) treated by atmospheric pressure plasma has been conducted. As the process parameters, we chose frequency, gas flow and treatment time. By measuring the contact angle, we scrutinized the effects of these parameters on the hydrophilic surface characteristics of polymer materials and found the optimum operating condition of each polymer for the highest hydropilicity. In the case of PC substrate, the contact angle was changed from 83.5 ± 1.1° (before plasma treatment) to 30.4 ± 0.4° (after plasma treatment) at the optimum operating condition of 30 kHz, CDA 0.6%, and repeated number of 7. In the case of PET substrate, the contact angle change was found from 59 ± 1.1° to 23.5 ± 1.7° at 20 kHz, CDA 0.6%, and repeated number of 7. In the case of EVA substrate, the contact angle of 84 ± 0.6° changed to 44.2 ± 1.2° at 30 kHz, CDA 0.6%, and repeated number of 7. The long-term stability of the hydrophilic surfaces and section morphology were also examined by SEM. As a roll-to-roll application, the adhesion force between PET and UV resin was measured to show initial increase according to the plasma treatment time, i.e., repeated number but finally saturated to show no meaningful change, which is in line with the behavior of the contact angle according to plasma treatment time.