Eco-friendly Dyeing of Polyester Fabric with Natural Madder Dye Using Supercritical Carbon Dioxide

The replacement of water with supercritical carbon dioxide (scCO₂) as a solvent in dyeing textiles is an emerging technology that allows sustainable dyeing by minimizing energy and chemical usage. In this study, scCO₂ dyeing of polyester fabric using madder as a natural dye was investigated and optimized without the use of any other chemicals. Response surface methodology and Box–Behnken design were utilized to design the experiments and optimize the effects of dyeing temperature, pressure, and time on the color strength of the dyed fabrics. According to the experimental design, a set of 15 dyeing trials were carried out, and the color coordinates and color strengths of the samples were measured. Among several models, the quadratic model exhibited the best fit to the experimental data, while temperature had the most significant influence on color strength. According to the established model, the optimal conditions were suggested as 118 °C, 20 MPa, and 73 min. The dyed fabric exhibited good washing and rubbing durability properties because the dye successfully diffused into the fabric. This offers a promising alternative to conventional high-temperature, high-chemical polyester dyeing methods.