Effect of non-thermal sulphur hexafluoride cold plasma modification on surface properties of polyoxymethylene

This paper deals with the surface modification of polyoxymethylene by the low-pressure non-thermal RF plasma using the sulphur hexafluoride plasma gas. The plasma treatment was performed based on various processing parameters including time, gas flow rate and plasma power. The effects were estimated on the basis of surface wettability determined by the water contact angle measurements. Morphological changes of the material surface were studied by scanning electron microscopy and optical profilometry. X-ray photoelectron spectroscopy was employed to reveal the differences in the chemical structure of the topmost layer after plasma modification. It was found out that changes in the surface properties of the polymer could be observed even after 20 seconds of treatment. The surface becomes hydrophobic or superhydrophobic, with the water contact angles up to 160 degrees. Morphological changes and increased roughness can be observed only in the nanoscale, whereas the structure seems to be unaffected in the microscale. As a result of plasma modification a permanent hydrophobic effect was obtained on the polyoxymethylene surface.