Improvement of hydrophobic properties of silk and cotton by hexafluoropropene plasma treatment

Plasma surface-treatment of silk and cotton fabrics were carried out in a hexafluoropropene (C₃F₆) atmosphere under different experimental conditions. Analysis of the treated fibers by X-ray photoelectron spectroscopy (XPS) indicated about 50 at% fluorine atoms were incorporated in the surface structure of two fibers and confirmed the presence of -CF, -CF₂, -CF₃ groups on the surface. After water-washing and alcohol-extraction, though partial loss of fluorine from the surface has been observed, contact angle and wet-out time measurements on the fibers still show much improved hydrophobic properties. The other properties of the treated fabrics, such as water vapor permeability and tensile strength were also evaluated.