Sustainable and eco-friendly strategies for polyester-cotton blends dyeing in supercritical CO2

• Three s-triazine reactive disperse dyes were synthesized. • Sustainable and waterless dyeing of polyester-cotton blends was investigated. • One-bath dyeing was successfully realized in supercritical CO 2 . • Dyeing mechanism of polyester-cotton blends was proposed. Traditional water medium dyeing of polyester-cotton fabrics consumes more water and energy, and causes serious environmental pollution in comparison with one-bath dyeing of single component fiber. To achieve sustainable dyeing of polyester-cotton blends, three reactive disperse dyes with s-triazine reactive group were synthesized, and supercritical CO 2 was used as solvent to conduct the waterless dyeing. The results showed that one-bath dyeing of polyester-cotton blends could be successfully realized with the synthesized dyes. Dyeing performance of the synthesized dyes was constantly improved with the extension of carbon chain on aniline. Compared with other two dyes, the optimal color strength of polyester-cotton blends was obtained with dye 3 using dimethylsulfoxide as co-solvent, and K/S values up to 6.4 were obtained at 100 °C, 20 MPa and 120 min with a dimethylsulfoxide concentration of 80 %. σ K/S values below 0.14 and washing and rubbing fastness above 4 were displayed for the colored samples. In addition, dyeing mechanism of polyester-cotton fabrics with the synthesized dyes was discussed combined with FT-IR measurement and stripping experiments.