Low-Temperature Wet-Cross-linking of Silk with Citric Acid

We report the development of a novel method of improving the wet wrinkle recovery of silk fabrics without affecting the whiteness or the tensile properties of the cross linked fabrics. Previous attempts on cross linking silk with poly(carboxylic acids) have been done in the dry state at high temperatures (150-175 degrees C) in the presence of the toxic catalyst, sodium hypophosphite, with decrease in the whiteness and tensile properties of the cross linked fabrics. In this research, citric acid (CA) was used to cross-link silk in the wet state at low temperatures using weak acidic to neutral pH as catalyst. The effect of cross linking conditions on the wrinkle recovery, whiteness index and yarn tensile and fabric tear strength were studied. The durability of the cross linking to laundering was also examined. The new method of cross-linking improves the wet wrinkle recovery of the silk fabrics by about 32% compared to the noncross-linked fabric without affecting the whiteness or the tensile properties of the fabrics. The improvement in the functional properties of silk was stable to multiple launderings.