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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.

The salt‐free reactive dyeing of cotton fabric meets the need of the modern textile industry and overcomes the problems posed by salt usage. In this study, a pad‐irradiate‐pad‐steam (PIPS) process for the salt‐free dyeing of cotton fabric with a reactive dye was applied. In this process, 3‐chloro‐2‐hydroxypropyltrimethylammonium chloride (CHPTMAC) was used to modify the fabric with cations under microwave heating. Then, the cationic fabric was dyed using a reactive dye. The influence of the cationising conditions in the PIPS process on the K/S value of the dyed cotton fabric was investigated. The results showed that the CHPTMAC concentration, the mole ratio of sodium hydroxide to CHPTMAC, the microwave irradiation power and the treatment time had significant effects on the dyeing of cotton fabric. Also, fastness to light, washing, and rubbing of the dyed cotton fabric was satisfactory.

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Severe effluent pollution has set new requirements for eliminating the use of salts during the reactive dyeing of cotton. In this study, 3‐chloro‐2‐hydroxypropyltrimethylammonium chloride was used as an etherifying agent via a pad‐irradiate‐pad‐steam process with a reactive dye to cationize cotton. The fabric underwent a microwave‐assisted pad‐irradiate process, and the cationic fabric was dyed salt‐free using a reactive dye in a pad‐steam process. The influence of etherifying conditions on the nitrogen content, grafting efficiency of the cotton samples, and dyeing properties of cationic cotton fabrics were investigated. Cationic cotton samples have the same dyeability with a reactive dye without salt as with dyes used in a conventional pad‐dry‐pad‐steam process because of the increase in the electrostatic attraction between the dye and the cationic cotton. Such an approach that eliminates salts is beneficial to environmental protection. Properties of the dyed cotton (such as color evenness, washing, and rubbing fastness) obtained using the reactive dye made the cotton fabric wearable enough to satisfy standard requirements.