Wettability and dyeability modulation of poly(ethylene terephthalate) fibers through cold SF6 plasma treatment

Surface modification induced on poly(ethylene terephthalate) (PET) fibers by cold SF6 plasma treatment has been investigated systematically as a function of plasma device parameters. The observed wettability modifications of fibers plasma-treated under different operating conditions were correlated to their dyeability modifications and to the changes in surface chemical composition, determined by X-ray Photoelectron Spectroscopy (XPS), and topography, investigated by atomic force microscopy (AFM). Optical emission spectra from the SF6 plasma at different pressures gave information on its content of fluorine atoms. A striking transition was observed between the increased hydrophilicity and high dyeability, imparted by plasma treatment at low pressure (< 0.2 mbar), mainly as a consequence of surface etching and surface activation, and the increased hydrophobicity, imparted by plasma treatment in the higher pressure regime (0.2-0.4 mbar), consequent to extended surface fluorination.