Atmospheric-pressure spin plasma jets processing of polymethylmethacrylate surface using experimental design methodology

Atmospheric-pressure spin plasma jets (APSPJs) have been developed to induce surface modifications on polymethylmethacrylate (PMMA). In this study, an experimental design methodology was used to investigate the influence of process parameters [such as radio frequency (RF) power, processing gap, and number of treatment cycles] on the characteristics of PMMA surface treated by APSPJs. It was observed from the atomic force microscope (AFM) and scanning electron microscope (SEM) results that the surface morphology of PMMA treated by direct plasma is much rougher than that treated by remote plasma. The direct plasma used in APSPJs processing created a substantial amount of nanostructure grains. Moreover, the measured XPS results showed that the O/C ratios of the PMMA surface were substantially increased and subsequently water contact angle decreased on direct plasma treatment. This decrease is due to an increase of oxygen-containing functional groups on the PMMA surface by the APSPJs processing. From the statistical analysis, the RF power and the processing gap were found to play a major role in enhancing the hydrophilic properties of PMMA surface. In contrast, the number of treatment cycles played only a secondary role in this case. Finally, in this study the APSPJs processing was demonstrated to be an effective method for surface modification of PMMA by controlling processing parameters during the treatment process. Copyright (C) 2009 John Wiley & Sons, Ltd.