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 NaH2PO2 takes place when the temperature rises above 200 degreesC. In this research, we use Fourier transform infrared (FTIR) spectroscopy and thermal analysis to confirm that NaH2PO2 reacts with cis-l,2-cyclohexanedicarboxylic anhydride (CHDN) at temperatures above 170 degreesC. NaH2PO2 catalyzes 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 degreesC. However, no esterification takes place on the fabric at such temperatures. The data also indicate that NaH2PO2 reacts with the anhydride intermediate when the temperature rises above 180 degreesC. We have found that esterification of cotton cellulose by BTTA takes place only when NaH2PO2 is present and the temperature is above 180 degreesC. Therefore, the catalysis effects of NaH2PO2 for cotton esterification by BTTA are probably related to the reaction between NaH2PO2 and the anhydride intermediate.