Evaluation of polymer hydrophobic recovery behavior following H2O plasma processing

Inductively coupled radio frequency (rf) H2O vapor plasma was used to modify a range of polymers to better elucidate the dependence of hydrophobic recovery on polymer composition and structure. Freshly modified and aged samples were examined using scanning electron microscopy, (SEM), X-ray photoelectron spectroscopy, (XPS), and water contact angle (wCA) goniometry. Initially, wettability was increased on each polymer surface due to the implantation of polar oxide groups, an effect exacerbated by increased surface roughness with plasma treatment. Polypropylene and polystyrene exhibit nearly complete hydrophobic recovery as polar groups are subsumed as samples age. High-density polyethylene and polycarbonate exhibit minimal hydrophobic recovery, owing to plasma-induced cross-linking and intrinsic thermal stability, respectively. Overall, the hydrophobic performance following H2O plasma modification is similar to other oxidizing plasmas, suggesting that recovery behavior is intrinsic to the polymer. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41978.