Enhancement of the hydrophobicity of silk fabrics by SF6 plasma

Hydrophobic properties are of interest in fabric and textile manufacture. We have used radio-frequency inductively coupled SF₆plasma to modify the surface of Thai silk fabrics for the enhancement of the hydrophobic property. The water contact angle of fabrics increased from 0°up to 145°after SF₆ plasma treatment. The measured water absorption time was found to depend upon the treatment time and RF power, for SF₆ pressures lower than 0.05 Torr. At higher SF₆ pressures, all samples achieved absorption times in excess of 200 min, regardless of the treatment time and RF power. The morphology changes of fabrics after plasma treatment were characterized by scanning electron microscopy and atomic force microscopy. After plasma treatment, the RMS surface roughness of the fibres increased from about 10 to 30 nm. From X-ray photoelectron microscopy analysis, we found that the hydrophobicity of the fabrics is the highest when the fluorine/carbon ratio at the surface increases. A small decrease of the oxygen/carbon ratio was also observed on the fabrics that showed the longest absorption times.