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Cotton is one of the world’s most common natural clothing materials. It is dyed mainly using the exhaustion, cold pad-batch, and pad-dry-pad-steam dyeing methods. The K/S value, an important index for measuring the depth of color, of cotton fabric dyed with reactive dyes is greatly influenced by various factors of the dyeing process. In this study, three models were developed incorporating least squares support vector machine (LSSVM) to predict the K/S values of dyed cotton fabrics, while particle swarm optimization (PSO) was applied to optimize and tune the parameters of the LSSVM model (PSO-LSSVM). Model inputs include dye concentration and process conditions, which are both easily obtainable variables. The K/S values from the PSO-LSSVM model are consistent with actual measured K/S values of dyed cotton fabrics. Moreover, a comparison among PSO-LSSVM, LSSVM and back propagation neural network results shows the superiority of the PSO-LSSVM approach. Results of this work indicate that a PSO-LSSVM model is a powerful tool for predicting the K/S value in cotton fabric dyed with reactive dye and thus a means to improve production processes and reduce costs.

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Response surface methodology is widely used in the optimization of dyeing conditions. Herein, the color strength and dye fixation rate of the cotton fabric dyed by pad-irradiate-pad-steam (PIPS) process were determined and compared to by conventional paddry-pad-steam (PDPS) process. Then the response surface methodology and central composite design were used to optimize the cationizing conditions during the padirradiation step of the process to obtain high color strength during the subsequent salt-free reactive dyeing of the cotton fabric via a pad-steam process. The obtained experimental data were fitted to the second-order polynomial equation, and response surface plots and contour plots were used to identify the optimal cationizing condition, the 3-chloro−2-hydroxypropyltrimethylammonium chloride concentration of 104 g/L, the microwave irradiation power of 537 W, the treatment time of 6 min, and the molar ratio of sodium hydroxide to 3-chloro-2-hydroxypropyltrimethylammonium chloride of 1.02. The results showed that the experimental color strength of the cotton fabrics was in close agreement with the value predicted by the model and the optimal cationizing condition was obtained precisely. K E Y W O R D S central composite design, pad-irradiate-pad-steam process, reactive dye, response surface methodology, salt-free dyeing