Dyeing of Modified Acrylic Fibers with Indigo Carmine: Modeling and Optimization of the Dyeing Process Using a Combination of RSM and ANN Methodologies

Indigo is a desirable deep-blue color for fabrics worldwide. However, the use of an alkaline medium to obtain the leuco-indigo is a great obstacle to dyeing acrylic fibers with indigo due to its sensitivity to alkalis. In the present study, the possibility of dyeing acrylic fibers with an indigoid dye has been explored for the first time. The use of the soluble indigo carmine allows to avoid the reduction step of indigo carried out in an alkaline medium. The nonpolarity and low indigo carmine affinity of acrylic fibers were investigated. To obtain a satisfying dyeing quality, a cationic agent was used to treat the acrylic fiber before dyeing with the acid dye indigo carmine. Infrared spectroscopy and scanning electron microscopy were used to suggest changes in the modified acrylic structure. Furthermore, the influence of the physico-chemical parameters (dye concentration, pH of the dyeing bath, temperature, and time) on dyeing performances (color strength and dye bath exhaustion) were then studied. Modelization and optimization of the dyeing process were realized via a method that combines artificial neural network and response surface methodology (RSM). The modeling of the dyeing process using the neural network method showed a good correlation between experimental values of color strength and the predicted ones. Thus, the effect of the main factors and surface plots was investigated using RSM. The obtained optimum dyeing conditions of modified acrylic fibers correspond to a dye percentage (6%), pH (3.5), time (68 min), and temperature (100 °C). It was found that this dye gives certain brightness and brilliance shades that are difficult to obtain with basic dyes. Finally, the dyeing fastness and the mechanical properties of acrylic fabric were discussed. The obtained results revealed that modified acrylic fabric presented good fastness and mechanical properties.