Evolution of the Surface Wettability of PET Polymer upon Treatment with an Atmospheric-Pressure Plasma Jet

A useful technique for pre-treatment of polymers for improved biocompatibility is surface activation. A method for achieving optimal wettability at a minimal thermal load and unwanted modifications of the polymer properties is elaborated in this paper. Samples of polyethylene terephthalate polymer were exposed to an atmospheric-pressure plasma jet created by a high-impedance low-frequency discharge in wet argon. Different treatment times and distances from the end of the glowing discharge enabled detailed investigation of the evolution of surface activation. A rather fast saturation of the surface wettability over the area of the order of cm2 was observed upon direct treatment with the glowing discharge. At a distance of few mm from the glowing discharge, the activation was already two orders of magnitude lower. Further increase of the distance resulted in negligible surface effects. In the cases of a rapid activation, very sharp interphase between the activated and unaffected surface was observed and explained by peculiarities of high-impedance discharges sustained in argon with the presence of impurities of water vapor. Results obtained by X-ray photoelectron spectroscopy confirmed that the activation was a consequence of functionalization with oxygen functional groups.

Influence of Ion Nitriding Regimes on Diffusion Processes in Titanium Alloy Ti-6Al-4V

The paper reports on the results of two-stage-experiments of low-temperature ion nitriding of the Ti-6Al-4V titanium alloy in a non-self-sustained high-current arc discharge and in a glow discharge under various conditions. The diffusion of nitrogen into the interior of the material was determined by the thickness of the layer being modified. It was established that the depth of the nitrided layer greatly depends on temperature, composition of the working medium, as well as on process duration. When treated in non-self-sustained high-current arc discharge, the depth of the nitrided layer increases from 4 to 17 μm, and in the glowing discharge the depth increases from 9 to 13 μm. The nitriding temperature affects the sign and magnitude of the residual stresses.