Process diagnostics in atmospheric continuous plasma equipment for fabric and polymeric film treatment

An equipment for atmospheric continuous treatment applicable to various textile materials was investigated to characterize its thermal, energetic, hydrodynamic and chemical features. The main characteristic of this prototype is provided by the peculiar fashion of contacting the fabric by the gaseous plasma blade jet. The operative variables of the process are gas flow rate and composition, electrical power to the plasma generator, fabric velocity, distance from gas inlet to accommodate different textile structures, as well as the impact gas-to-fabric angle. The diagnostics on the equipment was carried out to improve the plasma treatment homogeneity and generate an effective feedback analysis to the prototype manufacturer. The gas inlet was characterized in terms of thermal and gas velocity transversal profiles; in addition, the residual oxygen concentration was measured along the fabric motion direction and with a stimulus/response dynamic technique, i.e. after commuting the gas feed from air to pure nitrogen at several flow rates. The fabric itself was monitored by six infrared sensors downstream of the gaseous plasma contact. Besides the local property profiles, the comprehensive effect of the energy transferred to the moving substrate was evaluated by the blackening intensity on a thermal paper by reflection spectrophotometry. All these measurements have shown that the prototype definitely requires substantial improvements as far as the gas distribution is concerned to fully demonstrate its excellent potentiality to in-line functionalize textile substrates; further operative variables can also be controlled in a second release of this prototype.