FTIR Spectroscopy Study of Ester Crosslinking of Cotton Cellulose Catalyzed by Sodium Hypophosphite

In previous research, we found that sodium hypophosphite (NaH2PO2) reduces the temperature required for the formation of anhydride intermediates by polycarboxylic acids. We also found that a chemical reaction between the anhydride intermediate of 1,2,3,4-butanetetracarboxylic acid (BTCA) and NaH2PO2takes place when the temperature rises above 200°C. In this research, we use Fourier transform infrared (FTIR) spectroscopy and thermal analysis to confirm that NaH2PO2reacts with cis-1,2-cyclohexanedicarboxylic anhydride (CHDN) at temperatures above 170°C. NaH2PO2catalyzes the formation of the cyclic anhydride intermediate by 3-butene-1,2,3-tricarboxylic acid (BTTA) on cotton. In the presence of NaH2PO2, BTTA forms a five-membered cyclic anhydride on cotton at temperatures as low as 120°C. However, no esterification takes place on the fabric at such temperatures. The data also indicate that NaH2PO2reacts with the anhydride intermediate when the temperature rises above 180°C. We have found that esterification of cotton cellulose by BTTA takes place only when NaH2PO2is present and the temperature is above 180°C. Therefore, the catalysis effects of NaH2PO2for cotton esterification by BTTA are probably related to the reaction between NaH2PO2and the anhydride intermediate.