Low-energy hydrogen ion shower (LEHIS) treatment of polytetrafluoroethylene (PTFE) materials

The wettability and optical transmittance properties of hydrogen ion treated polytetrafluoroethylene (PTFE) materials were evaluated using contact angle, laser irradiation, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) tests. The materials were processed using low-energy hydrogen ion shower (LEHIS) produced by a gas discharge ion source (GDIS). The duration of treatment and ion shower energy were varied to determine their effects on the PTFE specimens. Mass spectrometry showed the ion shower constituents to be H+ and H2+ species. Within the bounds of the discharge conditions, flux density for the Hn+ beam measured a minimum of 0.06 A/m2 and a maximum of 0.25 A/m2. Both one- and two-way analysis of variance were employed to assist in the interpretation of the empirical data. Results showed that treatment using lower plasma discharge currents (Id) improved material hydrophobicity with contact angles measuring a high of 115° while higher Id resulted in enhanced hydrophilicity reducing contact angles down to 61°. Transmittance and wettability were found to correlate, i.e., a surface made more wettable became optically transmissive allowing as much as 99% signal transmittance. Conversely, a surface made more hydrophobic reduced light leakage to as low as 60%. As the material showed increased surface striations, its optical transmittance, wettability, and surface tension also increased. With no observable shifting of the IR-absorption peaks, the surface modification was essentially morphological in character.