Surface modification of polymer using AC-pulsed plasma: Optimization of the electrical parameters and characterization by contact angle and probe-tack tests

This study is devoted to the surface modification of a glassy polymer (polycarbonate) using a non-equilibrium AC-pulsed plasma treatment in a 2 mbar-nitrogen atmosphere. The duty factor of the power supply lies between 5% and 100%. During the pulse inside which the plasma is on, a 50 kHz-sinusoidal voltage is applied between parallel plate electrodes separated by a 1.5 cm gap. The surface characterization is made with the well-known contact angle method. In addition, we show that a lab-made probe-tack test, less common for this kind of experiments, can be used for surface analysis as well. A few results on the chemical characterization of the treated surfaces are given. As regards to the plasma process, it is shown that for the treatment time, the power and the energy remaining at constant values, the wettability can still be improved by acting on the temporal distribution of the energy into the discharge, i.e. without further energy consumption.