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

In previous research, we found that sodium hypophosphite (NaH ₂ PO ₂ ) 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 NaH ₂ PO ₂ takes place when the temperature rises above 200°C. In this research, we use Fourier transform infrared (FTIR) spectroscopy and thermal analysis to confirm that NaH ₂ PO ₂ reacts with cis-1,2-cyclohexanedicarboxylic anhydride (CHDN) at temperatures above 170°C. NaH ₂ PO ₂ catalyzes the formation of the cyclic anhydride intermediate by 3-butene-1,2,3-tricarboxylic acid (BTTA) on cotton. In the presence of NaH ₂ PO ₂ , 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 NaH ₂ PO ₂ reacts 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 NaH ₂ PO ₂ is present and the temperature is above 180°C. Therefore, the catalysis effects of NaH ₂ PO ₂ for cotton esterification by BTTA are probably related to the reaction between NaH ₂ PO ₂ and the anhydride intermediate.