Formation of cyclic anhydride intermediates and esterification of cotton cellulose by multifunctional carboxylic acids: An infrared spectroscopy study

Multifunctional polycarboxylic acids have been used as nonformaldehyde crosslinking agents for cotton fabrics to replace the traditional N-methylol reagents. Esterification of cotton cellulose by seventeen aliphatic and aromatic polycarboxylic acids is studied using Fourier transform infrared spectroscopy. Five-membered cyclic anhydride intermediates formed under the curing conditions are identified on cotton fabrics treated with these acids. Only those polycarboxylic acids that form cyclic anhydride intermediates esterify cotton cellulose. Formation of the cyclic anhydride intermediates and esterification of cotton cellulose take place in the same curing temperature regions. The infrared spectroscopy data also indicate that the second carboxyl group in a bifunctional carboxylic acid is not able to esterify cotton cellulose effectively. Therefore, we can conclude that a polycarboxylic acid esterifies cotton cellulose through the formation of a cyclic anhydride intermediate. The infrared spectroscopy data also reveal that 1,2,3,4-butanetetracarboxylic acid is the most effective crosslinking agent for cotton cellulose among the acids studied.