Abstract

Polypropylene (PP) films are locally plasma treated with a single line pattern using a plasma needle set-up with micro scale accuracy and resolution. The two main plasma treatment conditions, number of treatment repeats and applied power, have been varied and their influence on the surface characteristics has been investigated. X-ray photoelectron spectroscopy (XPS) mapping measurements have been carried out to show the distribution of oxygen functional groups across sections of the plasma treated line patterns. These measurements have been correlated with water contact angle (WCA) results and showed that the created polar oxygenated functionalities are responsible for a sharp local increase in wettability. Increasing power and treatment repeats resulted in an improvement in wetting behavior of PP films and led to wider tracks with higher percentages of incorporated oxygen across the treatment patterns. AFM analysis of a treated straight line also showed that the center of the track line has a higher roughness than the border parts. Increasing power and number of treatment repeats results in a progressive increase of surface roughness and the generation of a granular topography. It has been shown that increasing the power has a more pronounced effect on the PP morphology than the variation of treatment time. (C) 2016 Elsevier B.V. All rights reserved.