The investigation on dark dyeing properties of silk using Dioscorea cirrhosa Lour. tuber extracts with varied molecular weights

Abstract

This work reported the dark dyeing properties of Dioscorea cirrhosa Lour. tuber extracts with different molecular weights on silk. The study on component analysis indicates that the molecular weight of most condensed tannins and polyphenols in D. cirrhosa L. tuber extracts is higher than 1000. The kinetic study demonstrates that the adsorption processes of D. cirrhosa L. tuber extract components with molecular weights higher than 1000, and components with molecular weights lower than 1000 toward silk fabrics are fitted with the pseudo-second order model, and the survey of adsorption isotherms reveals that multiple interactions occurred between dyes and silk, encompassing hydrogen bonding and van der Waals forces. The dyeing research shows that the dyed silk achieves its darkest color when employing D. cirrhosa L. tuber extract components with molecular weights lower than 1000 with a Fe2+ mordant concentration of 4 g/L and a pH value of 5. The K/S and L* values of dyed silk are 9.05 and 30.77, respectively. Under this dyeing condition, the complex, Fe element content, and Fe2+ ratio on the silk dyed with D. cirrhosa L. tuber extract components with molecular weights lower than 1000 surface are higher than those of D. cirrhosa L. tuber extracts and D. cirrhosa L. tuber extract components with molecular weights higher than 1000. The present study indicates that condensed tannins in D. cirrhosa L. tuber extracts are not the sole active compounds involved in the silk dark dyeing process. Polyphenols with molecular weights below 1000 in D. cirrhosa L. tuber extracts are shown to influence significantly and, in some cases, dominate the silk dark dyeing process.