Optimizing Dyeing Parameters for Indigo on Cotton Yarn: A Comparative Study of Exhaust Dyeing and Continuous Dyeing Techniques

This research work investigates the dyeing process of 100% cotton yarn samples with indigo dye using the exhaust method. The study focuses on the effects of various dyeing factors, including dipping time, temperature, and oxidation time, using a Box–Behnken statistical design. Experimental results were analyzed through response surface curves to comprehensively assess the impact of these factors on color yield and color tone. These findings offer valuable insights into the exhaust dyeing process of indigo on cotton yarn, highlighting the crucial role of dipping time, temperature, and oxidation time in achieving desired dyeing outcomes. The study demonstrates that extending the dipping time and oxidation time resulted in higher K/S values, indicating enhanced dye adherence. However, the higher values of temperature negatively affects dye uptake. The research additionally contrasts the exhaust dyeing technique with continuous dyeing, wherein the yarn samples underwent dyeing in four and eight consecutive baths, respectively. The yarn samples dyed through exhaust dyeing exhibit a lighter shade with a tendency toward a more bluish tone when compared to yarn dyed using continuous dyeing. Nonetheless, the continuous dyeing method provides a layer-by-layer uniform dyeing effect, recognized as the ring dyeing effect. Additionally, cross-section analysis reveals that exhaust dyeing allows for higher penetration of indigo dye compared to continuous dyeing.