Mordant Free Dyeing and Functionalization of Wool Fabrics with Biocolorants Derived from Apocynum venetum L. Bast

Biomass has emerged as a sustainable and renewable resource for dyestuff production. There is an increasing interest in biocolorants, especially in pigments from herbs. Nevertheless, hazardous metal mordants need to be used in conventional dyeing procedures to achieve the desired exhaustion rate and colorfastness. In this study, a novel dyeing strategy was presented for wool fibers with flavonoid pigments extracted from the bast of Apocynum venetum L. (A. venetum) based on in situ polymerization and covalent fixation of the dyes on the fiber. A new dyeing process was developed using NaOH as a dye fixative in the absence of mordants. The dyed fabric obtained by employing a relatively low NaOH concentration of 1.0 g/L in the dyebath, at a constant dyeing temperature of 100 °C, a dyeing time of 90 min, and a fixation time of 30 min, had a significant improvement in the color strength as well as the antibacterial activity against the assayed microorganisms, in addition to the good rubbing and washing colorfastness. Moreover, it was found that the wool dyed under optimum conditions suffered almost no damage from the tensile test results. This biodyeing strategy provided a new way for the sustainable wool dyeing process.