PTFE is a chemically inert and highly hydrophobic fluoropolymer due to the high electronegativity of fluorine. It is not readily modified by standard plasma processes but the may be altered to render the surface hydrophilic by the use of hydrogen plasma. The action of atomic hydrogen, generated by the plasma, is to react with surface fluorine and remove this into the gas phase where it is pumped away by the vacuum system. Hydrogen then terminates the free surface bonds to produce a CHx polymer surface which is readily wettable. The resulting surface is also ‘etched' on a microscopic scale which produces a microscopically structured surface. Both actions in combination result in a modified surface which may be glued, painted etc.
Plasma Treatment, of PTFE
Warrington, UK | Posted on February 13th, 2015
When gas atoms are ionised, the collision of high energy particles knocks electrons out of their orbits. This results in the characteristic "glow" or light associated with plasma. Plasmas many different species including atoms, molecules, ions, electrons, free radicals, metastables, and photons in the short wave ultraviolet (vacuum UV or VUV) range. Plasmas are generated in closed vessels at low pressures, typically < 1.0 Torr. The low pressure results in a long mean free path of the plasma species, so that they remain reactive until contact with a surface. The overall chamber temperature at the commonly used power levels and pressures is close to room temperature.
The altered surface morphology and results of surface energy test fluid measurements (72mN/m) are shown in images.
"Treatment of PTFE with low pressure hydrogen plasma is a very effective method of rendering the surface wettable without using harsh chemicals."