Stability of cold plasma improved wettability and adhesive property of polytetrafluoroethylene surface

In this paper, we investigate the wettability change of APCP-treated PTFE surfaces with time under different storage temperatures and pressures, and the results indicate that low temperature can hinder the wettability recovery. After storing for 5 days, WCA of PTFE stored under room temperature (25 degrees C) recovered from 19 +/- 2 degrees to 54 +/- 2 degrees, while the WCA of PTFE stored under low temperature (-10 degrees C) just increased to 42 +/- 3 degrees. Then, the mechanism contributing to the slower wettability recovery was investigated by analyzing surface chemical compositions via X-ray photoelectron spectroscopy (XPS) and observing surface morphologies using atomic force microscope (AFM). After 15 days storage, the contents of O and N decreased obviously, while F content increased. The F content of sample stored under low temperature was 20% less than that stored under room temperature. By contrast, surface micro-morphologies remained unchanged during storage, and the surface roughness Ra of each sample was around 7 nm. Finally, peel strength tests were conducted on APCP-treated PTFE surfaces stored under different temperatures, and the surfaces stored under low temperature maintained better adhesive property; 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 significantly facilitate practical applications of APCP modification and PTFE surfaces.