This study investigated the overdyeing process of nylon knitted fabrics using two natural plant dyes—indigo and turmeric—to address the high pollution associated with synthetic dyes and the limited color gamut of natural dyes. Through single-factor experiments, the dyeing parameters were optimized to achieve yellow-green and blue-green hues. The dyeing performance, color fastness, and antibacterial properties of the dyed fabrics were evaluated. The optimal conditions for yellow-green shades were: indigo 5 g/L, glucose 10 g/L, NaOH 1 g/L, liquor ratio 1:50, reduction at 60 °C for 30 min, oxidation at room temperature for 30 min; followed by turmeric 1.2 g/L, liquor ratio 1:60, dyeing at 80 °C for 20 min. For blue-green shades: indigo 10 g/L, turmeric 0.8 g/L, dyeing at 50 °C, with other parameters identical. Both overdyed fabrics exhibited color fastness of grade 4 or higher, meeting apparel requirements. Antibacterial rates against Staphylococcus aureus and Escherichia coli reached 99% and 98%, respectively. These results confirm the feasibility of applying natural plant dyes to nylon fabrics and provide a reference for sustainable textile dyeing.
Wu et al. (Sat,) studied this question.