Surface modification of Polyurethane sheets using an atmospheric pressure RF plasma jet in helium/oxygen gas mixture*

Atmospheric pressure non-thermal plasmas have become increasingly prevalent within many research and industrial applications due to their range of reactive gas species produced. In this work, an atmospheric pressure RF plasma jet sustained in helium/oxygen gas mixture has been used to modify the surface of polyurethane sheets. The diffused atmospheric pressure cold plasma system is a capacitive coupled radiofrequency (RF) plasma with low gas temperatures. The gas temperature of the plasma jet was found to be few degrees above room temperature at 3-5 mm away from the nozzle. Characterization of the plasma jet plume has been done and reactive species were identified. Plasma power was in the range of 60-180 Watt. Polyurethane sheets have been plasma treated with helium/oxygen gas mixture under standardized power to flow rate ratios. The effect of distance and exposure time on the surface modification efficiency has been studied. In the second part of the work, the chemical and physical changes induced by RF plasma jet on polyurethane surfaces have been investigated by contact angle measurements and inverted material’s microscope using filtered reflected light. Surface energy of polyurethane was calculated through geometric mean equations using two liquids contact angle data. From these results, it was found that non-thermal atmospheric pressure RF plasma enhances the surface wettability of the polyurethane polymers. These experimental systems and data collected can be effectively used in various applications including surface processing and biomedical applications.