Surface Modification and Aging of Polyacrylonitrile Butadiene Styrene Polymer Induced by Treatment in RF Oxygen Plasma

Polyacrylonitrile butadiene styrene (ABS) was treated in a radio frequency oxygen plasma created at various powers in two discharge modes (E-mode and H-mode). After plasma treatment, which lasted for 2 s, the samples were analyzed using X-ray photoelectron spectroscopy, atomic force microscopy, and contact angle measurements, whereas plasma was characterized by an optical emission spectroscopy. The E-mode allowed for gentle functionalization, whereas the H-mode also for extensive etching. The water contact angle (WCA) dropped to approximately 20° even for the lowest power of 50 W (E-mode) and remained unchanged up to approximately 600 W (H-mode) when it started increasing slightly. Contradictory, the oxygen concentration on the surface was a few at% higher in the H-mode. Furthermore, a removal of the original CN groups in ABS surface layer was observed after treatment in the H-mode, indicating intense surface etching and degradation. All samples exhibited rapid hydrophobic recovery because the WCA increased up to 27° and 42° in one day for E-mode and H-mode, respectively. The recovery was slower when samples were stored in a fridge.