Optimization of the Mod-VIII One Atmosphere Uniform Glow Discharge Plasma Reactor® for Surface Energy Treatment

A plasma reactor system has been developed to provide roll-to-roll surface treatment of fabrics and films using an air plasma. Effects of air plasma surface treatment at one atmosphere can include etching, cleaning, sterilization, disinfection, and increasing surface energy, all without the use of chemical inputs and with minimal toxic by-products. Webs can be continuously and uniformly treated by proper control of gas flow, electrode configuration, plasma parameters, fabric speed, and fabric tension. Tests conducted in this work focused on raising the surface energy of PET and HDPE using various electrode configurations. For industrial applications, the exposure time required to make the surface wettable (having a contact angle less than 20 degrees) should be one second or less. The reactor system was tested with a variety of electrode geometries, two of the more successful of which were a variable gap curved-to-flat plate geometry that consists of a rotating, grounded, stainless steel drum in combination with a flat transparent upper electrode. In this configuration, a One Atmosphere Uniform Glow Discharge Plasma (OAUGDP)® exists at the minimum gap, but tends to transition to a filamentary glow discharge as the gap widens. This filamentation was minimized by proper gas flow and adjustment of the dielectric barrier configuration, reducing any negative impact on processing results. When a transparent electrode configuration is in use, the phenomenology of this unique plasma volume can be studied in situ in both the normal and transverse directions with respect to the electric field. Results are compared to previous experiments conducted in the Plasma Sciences Laboratory using static sample exposure, including effects of the exposure duration time and the ageing effect. Contact angle measurements based on the sessile water drop test were conducted to confirm proper operation and uniformity of effect