Effect of pH on Nonformaldehyde Durable Press Finishing of Cotton Fabric: FT-IR Spectroscopy Study

When the three sodium salts of phosphoric acid were used as catalysts for the ester crosslinking of cotton cellulose, they showed different levels of effectiveness due to the different pH values of the finish baths. In this research, the effect of finish bath pH on the esterification of cotton cellulose by 1,2,3,4-butanetetracarboxylic acid (BTCA) was investigated using Fourier transform infrared spectroscopy (FT-IR). FT- IR data indicated that the esterification by polycarboxylic acids is pH-dependent. When a cotton fabric was finished with BTCA without a catalyst, both the number of ester linkages formed in the fabric and the effectiveness of the bonded BTCA mol ecules first increased, then decreased as the pH of the finish bath increased from 1.5 to 5.5. An optimum pH range for esterification was determined. A similar phenomenon also occurred when a catalyst (phosphate or hypophosphite) was used. Therefore, it is necessary to choose the optimum pH range of a finish bath in order to achieve the most effective esterification.