Effects of DBD plasma operating parameters on the polymer surface modification

This paper, based on an orthogonal experimental design and analysis method, reports the effects of a dielectric barrier discharge (DBD) plasma surface treatment on polytetrafluoroethylene (PTFE), polyimide (PI) and poly (lactic acid) (PLA) films in terms of changes in surface wettability and surface chemistry. The purpose was to study the influence of the main operating parameters, i.e. plasma power, treatment period duration (treatment cycles) and electrode gap on the resultant surface properties. Statistical analysis was carried out to develop an equation which expresses surface properties (water contact angle and oxygen enrichment, as observed by XPS analysis) in terms of these operational parameters. It was observed that the plasma parameters have a selective effect on the changes observed for the polymers processed. In particular, plasma processing time (treatment cycles), plays an important role in the treatment of PTFE and PI in this study, whereas the size of the electrode gap plays the dominant role in the treatment of PLA. Fast surface activation can be achieved in all cases after only a few seconds of treatment duration. The wettability improvement observed in all cases was attributed to changes in both surface chemistry and surface micro-structure. (C) 2004 Elsevier B.V. All rights reserved.