Esterification crosslinking structures of rayon fibers with 1,2,3,4-butanetetracarboxylic acid and their water-responsive properties

1,2,3,4-Butanetetracarboxylic acid (BTCA) was applied to crosslink amorphous regions of cotton-type rayon fibers via anhydride-mediated esterification for the purpose of enhanced mechanical properties. Crosslinking was conducted under a series of curing temperature with the presence of sodium hypophosphite (SHP) as the effective catalyst for anhydride formation. The conversion rate based on Fourier transform infrared (FTIR) spectra was in good agreement with that from the direct calculation based on titrated carboxyl groups and ester linkages. Crosslinking degree increased linearly with the curing temperature. The optimal tensile properties were derived from the curing temperature of 180 °C with an intermediate crosslinking degree. Moreover, the crosslinked structures of the rayon fibers had a great impact on absorption of liquid and gaseous water. The liquid water retention capacity diminished substantially with the crosslinking degree, while interaction between moisture and the fibers revealed that sorption-desorption cycles and concomitant hystereses were scarcely affected by the crosslinked fiber structures.