Effects of plasma treatments on the surface wettability properties of PTFE polymeric films.

A cold cathode plasma source is constructed for modifying PTFE surface characteristics. The source was easily built, had a consistent plasma discharge medium and acceleration system. A cylindrical Langmuir probe is also used to evaluate plasma parameters like density, temperature or even plasma potential. This probe is designed to be moveable so that it may approach any desired position in the plasma volume. The influences of nitrogen pressure and probe-cathode gap on plasma parameters were investigated. The electron temperature T e fluctuated from 7. 7 3 × 1 0 4 to 6. 8 × 1 0 4 eV as the pressure rises from 0.2 to 0.4 mbar. Further, by increasing the cathode-probe gap from 0.4 to 2 cm, the electron densities increased from 0. 4 6 × 1 0 1 0 cm − 3 to 0. 8 9 × 1 0 1 0 cm − 3 . Furthermore, the contact angles, work of adhesion and surface free-energy of pristine as well as irradiated PTFE films, were estimated. The results demonstrated that by extending the plasma exposure duration from 0 to 12 min, the water contact angle is lowered from 82.2^∘ to 30.5^∘. At these conditions, the work of adhesion is raised from 81.9 to 134.1 mJ/m², as the surface free energy is increased from 29.8 to 71.8 mJ/m². [ABSTRACT FROM AUTHOR]