Studies on the surface free energy and surface structure of PTFE film treated with low temperature plasma

The surface free energy and surface structure of poly(tetrafluoroethylene) (PTFE) film treated with low temperature plasma in O2, Ar, He, H2, NH3, and CH4 gases are studied. The contact angles of the samples were measured, and the critical surface tension γc (Zisman) and γc (max) were determined on the basis of the Zisman's plots. Furthermore, the values of nonpolar dispersion force γas, dipole force γbs, and hydrogen bonding force γcs to the surface tensions for the plasma-treated samples were evaluated by the extended Fowkes equation. Mainly because of the contribution of polar force, the surface free energy and surface wettability of PTFE film which was treated with H2, He, NH3, Ar, and CH4 for a short time increased greatly. Electron spectroscopy for chemical analysis (ESCA) shows that the reason was the decrease of fluorine and the increase of oxygen or nitrogen polar functional group on the surface of PTFE. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1733–1739, 1997