Broadening Color Shade Range of Rubia tinctorum L. Natural Colorants on Wool Fibers via Combination of Metal Mordants: Color Characteristics and Fastness Studies

Abstract

This study aims to extend color shade range of Rubia tinctorum L. (Dyer’s madder) natural dye on wool textiles via binary combination of Al, Sn, Cr, Fe, Cu, Ni, Co, Zn mordants. Wool yarns were premordanted, dyed with 75.0%owf madder dye, and characterized for their color strength, colorimetric parameters, and color fastness. Nature of single and binary metal cations substantially affected color shades, color strength, and fastness properties due to different interactions of dye, metal mordants, and wool polymer chains. This resulted in the development of novel color shades having different lightness, enhanced color strength, and color fastness properties. Combination of mordants had a synergistic effect on dye uptake which enhanced color strength values. Moreover, with the aid of binary metal mordants, colors of some legally restricted mordants like chromium can be reproduced which is important from ecological viewpoint. Binary mordanted samples exhibited superior color fastness. Results represent that this viable method can extend the color gamut of madder natural dye on wool with satisfactory color fastness and lessen the hazards associated with the use of some toxic metal mordants.