Experimental study of temperatures of atmospheric-pressure nonequilibrium Ar/N2 plasma jets and poly(ethylene terephtalate)-surface processing

To understand the mechanism of surface processing using atmospheric-pressure nonequilibrium plasma jets, we measured the vibrational and rotational temperatures in the plasmas by optical emission spectroscopy. Plasma was excited using a high-frequency pulsed power supply, using a gas mixture of Ar (20 L/min) and N-2 (0.1 to 0.5 L/min) as the plasma gas, and changing the flow rate of N-2 gas at an input power of 100 W and plasma frequencies of 5 and 10 kHz. The measured vibrational and rotational temperatures in plasma were approximately 0.18 to 0.26 eV and 0.21 to 0.28 eV, respectively. We also carried out a plasma surface processing of polyethylene terephtalate film to measure the changes in water contact angle before and after the processing We found a monotonic decrease in the contact an-le of the processed poly(ethylene terephtalate) (PET) film as plasma rotational temperature increased. It is concluded that the hydrophilicity of the PET surface increases with plasma rotational temperature.