Sustainable Low-Pressure Air Plasma Pretreatment for Metallic Pigment Printing on Cotton Fabrics: Improved Surface Functionality, Fastness Performance and Reduced Environmental Burden

Conventional pretreatment methods used in metallic textile printing are associated with high water consumption, intensive chemical use and significant wastewater generation. This study investigates low-pressure air plasma treatment as an environmentally sustainable pretreatment strategy for metallic pigment printing on cotton fabrics. Grey and bleached woven cotton fabrics were exposed to air plasma at 200 W for 3 and 5 min before screen printing with gold- and silver-based metallic pigments. The effects of plasma treatment on fabric surface chemistry and morphology were evaluated using contact angle measurements, ATR-FTIR spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. Plasma treatment significantly increased the hydrophilicity of both cotton substrates, reducing liquid penetration time from 61 s to below 10 s for bleached cotton and from more than 20 min to 6 s for grey cotton. ATR-FTIR and XPS analyses confirmed the formation of oxygen-containing functional groups, while SEM images showed surface etching and increased roughness that enhanced pigment anchorage. The improved surface functionality translated into superior metallic print performance. Plasma-treated fabrics exhibited enhanced colour fastness to washing, rubbing, perspiration and light compared with untreated fabrics. The greatest improvement was observed after 5 min of plasma exposure, particularly for gold pigment prints. However, SEM analysis revealed that prolonged exposure (5 min) may lead to increased surface erosion, highlighting the need for careful optimisation to balance surface activation with preservation of fibre integrity. UV-visible spectroscopy of wash effluents demonstrated lower pigment release from plasma-treated samples, confirming improved pigment retention and reduced wastewater contamination. The results demonstrate that low-pressure air plasma treatment can replace conventional wet chemical pretreatments for metallic textile printing, offering substantial reductions in water use, chemical consumption and pigment discharge. The approach provides a practical route toward cleaner and more sustainable textile production, particularly for emerging textile industries.