The kinetics, activation energy, and mechanism of esterification of cotton by mixed polycarboxylic acids, namely, 1,2,3,4-butanetetracarboxylic acid (BTCA) and citric acid (CA), were studied during the curing process of cotton fibers in comparison with the esterification by BTCA alone. The reaction rates of these two polycarboxylic acid finishing systems under different temperatures and the dependency of their reaction rate constants on temperature were studied. Consequently, in the temperature range from 120°C to 180°C, the activation energy of the mixed polycarboxylic acids (BTCA+CA) was obtained as Ea=40.7 kJ/mol, which was slightly lower than that for the BTCA finishing system. The reaction occurring between the carboxylic acid group of BTCA and the hydroxyl group of CA was proposed. To confirm and prove the speculation, experiments were conducted to investigate the changes in wrinkle recovery angle and tensile strength retention by changing the concentration of both the single polycarboxylic acid and mixed polycarboxylic acids. The results show that, besides esterification of cotton fibers, citric acid probably functioned as an extender in the curing process, when it was combined with BTCA.

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Alginate fiber with a breaking tenacity of up to 2.32 cN/dtex is prepared by spinning a sodium alginate solution in a coagulating solution of CaCl2 aqueous solution followed by multi-roller drawing. Preparation parameters such as sodium alginate concentration, coagulant concentration and coagulation temperature, which affect the fiber tenacity, are investigated with an orthogonal test design, and the best spinning process is found with a coagulating 5% sodium alginate solution in 4% CaCl2 at 40°C. The morphology, degree of crystallinity, thermal stability and the combustion performance of this alginate fiber are investigated by scanning electron microscopy (SEM), infrared (IR), X-ray diffraction (XRD), Thermo gravimetric Analysis (TGA) and Cone Calorimeter. Using the centrifugal dewatering method, the absorption capacity of this alginate fiber is determined, and has a capacity of 13.01 grams of man-made blood per gram. The test results show that fibers have an irregular cross-section without a thicker cortex and uniform longitudinal surface with grooves. The combustion property results demonstrate that the fiber has a self-flameretarding property.

The compound 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) is an eco-friendly water treatment agent possessing flame-retardant phosphorus element and multi-carboxylic acid groups in its molecular structure. In the present work, PBTCA is employed as a finishing agent to improve the flame retardancy of the wool fabrics by the pad-dry-cure technique. The treated wool (10.2% weight gain) by 100 g/L of PBTCA showed an increased flame retardancy with a limiting oxygen index value (LOI) of 44% with a minimum char length of 40 mm. Importantly, the treated wool can self-extinguish after 30 washing cycles. The PBTCA-treated wool exhibited better stability with obviously increased char residue of 39.7% and 28.7% at 600 °C, while only 25.9% and 13.2% were measured for the control wool in nitrogen and air atmosphere, respectively. In addition, the high thermal stability of the treated wool with astonishing char-forming ability is confirmed by the SEM images of the wool after the isothermal heating treatment at different temperatures. Finally, a two-stage flame-retarding mechanism of enhanced crosslinking and char formability of PBTCA-treated wool is proposed and analyzed by infrared spectroscopy (TG-FTIR) and thermal (DSC and TGA) results of the pyrolytic volatiles of the treated wool.

Durable press (DP) finishing process of cotton fabric with 1,2,3,4-butanetetracarboxylic acid (BTCA) was investigated and optimized using the Box-Behnken design (BBD) with a response surface methodology (RSM). BBD experimental data were fitted to create the response surface regression models describing wrinkle recovery angle (WRA) and breaking strength of the finished cotton fabric. Analysis of variance (ANOVA) revealed that the concentration of BTCA was the most significant variable affecting the WRA, followed by the curing time, curing temperature, and concentration of sodium hypophosphite (SHP). Regarding breaking strength, curing time was the most significant variable, followed by the curing temperature, concentration of BTCA, and concentration of SHP. After optimal treatment, the WRA of the finished fabric was 252°, while the retention rate of breaking strength was 69%.