Study on the physical-morphological and chemical properties of silk fabric surface modified with multiple ambient gas plasma for inkjet printing

Abstract

The silk samples were treated by air, air/Ar and air/O 2 plasma at atmospheric-pressure to modify their physical-morphological and chemical properties for pigment ink-jet printing. By testing multiple ambient gas and different discharging time, it was concluded that the mixture of argon and especially oxygen made the plasma treatment more sufficient for enhancing the ink-jet printing performance. Unexpectedly, scanning electron microscope (SEM) reveals that there is no remarkable difference on surface morphology between original and modified samples. According to the result of X-ray photoelectron spectroscopy (XPS), the oxygen-containing radicals formed in plasma were introduced into the polymer chains of silk. Contact angle measurement indicates modified silk substrates are more hydrophilic than unmodified one. The bleeding resistance, color strength, shade and chroma of samples were investigated with the aim of evaluating the direct print properties of fabric. The anti-bleeding property of silk could be directly observed by the video zoom microscope. The color strength study proves that the modified sample has deeper color, darker shade and larger saturation. The recession experiments prove that the decline of the oxygen-containing groups started since the silk sample has been exposed to air. Nevertheless, the surface hydrophilicity of modified silk may reduce but not as completely ineffective as untreated sample. • The modification effect of atmospheric-pressure plasma is obviously strengthened after adding small amount of oxygen or argon with air. • Some hydrophilic polar groups, such as C－O, C=O and N－C=O, generated during plasma discharging were introduced onto fiber surface. • The active species in the plasma hit the surface of the fibers and reacted with silk molecules, making the fabrics more wettable. • The printing performance of silk was verified to be superior by the higher distinct printing edge and color yield.