Stability of plasma improved adhesive property of polytetrafluoroethylene surface

In this study, the authors investigated the wettability change of atmospheric-pressure-cold-plasma (APCP)-treated polytetrafluoroethylene (PTFE) surfaces with time under different storage temperatures and pressures, and the results indicate that low temperature can hinder wettability recovery. After storage for 5 days, the water contact angle (WCA) of PTFE stored at room temperature (25°C) recovered from 19 ± 2 to 54 ± 2°, while the WCA of PTFE stored at low temperature (−10°C) increased to just 42 ± 3°. Then, the mechanism contributing to the slower wettability recovery was investigated by analyzing surface chemical compositions through X-ray photoelectron spectroscopy and observing surface morphologies using atomic force microscopy. After 15-day storage, the oxygen (O) and nitrogen (N) contents decreased obviously, while the fluorine (F) content increased. The fluorine content of the sample stored at low temperature was 20% less than that of the sample stored at room temperature. In contrast, surface micromorphologies were unchanged during storage, and the surface roughness R _a of each sample was around 7 nm. Finally, peel strength tests were conducted on APCP-treated PTFE surfaces stored at different temperatures, and the surfaces stored at low temperature maintained better adhesive properties. After 15 days of storage, the adhesive strength could still reach 400 N/m, which was 376% higher than that of the untreated surface. The research results are expected to facilitate practical applications of APCP modification and PTFE surfaces significantly.