A salt-free, dyebath-recyclable nanoscale pigment dyeing technology for cotton fabrics based on the dispersed system of small cationic copolymer nanoparticles

The colouration of cotton fabrics through the charge attractions between cationic nanoscale pigment and cotton fabrics, is a novel pigment dyeing technology with the advantages of no salt, recyclable dyebath, high uptake, and good wet fastness. In this study, the cationic copolymer nanoparticle dispersants with a diameter of about 32 nm were synthesized by reversible addition-fragmentation chain transfer (RAFT) alcoholic dispersion poly-merization. The cationic nanoparticle-based nanoscale pigment dispersion was prepared, and its colloidal and dyeing properties were also investigated. The results indicated that the nanoscale pigment dispersion had good dispersion performance in the aqueous medium with relatively narrow distribution and excellent colloid stability against the external effects of centrifuge, freeze-thaw test, and pH, in which the cationic nanoparticles were indeed adsorbed on the surface of anionic C.I. pigment red 170 particles by electrostatic attraction. It was found that the salt-free cationic nanoparticle-based nanoscale pigment dyed cotton fabrics acquired higher coloring intensity and colour fastness due to establishing the charge attractions between nanoscale pigment and cotton. More importantly, the dyebath is recyclable for circular dyeing, as a result significantly reduces the discharge of dyeing effluent, which provides a viable and promising strategy for ecologically sustainable dyeing technology for cotton fabrics.