Comparison of natural dyes for wool, cotton and Lyocell fabrics under special consideration of titanium dioxalate as mordant

The application of natural dyes on natural fiber materials enables the realization of fully bio-based textile products. Usually natural dyes are applied in combination with mordanting agents to improve color strength and fastness properties. This current paper is dedicated to a comparison of the natural fibers wool and cotton with the regenerated cellulose fiber Lyocell. For natural dyeing, extracts from logwood or madder root are used as natural dyes. As mordanting agent, water soluble salts of Fe 2+ and Cu 2+ are evaluated in comparison to the less common agent titanium dioxalate, which is a water soluble chelate complex of Ti 4+ . Applications are done as pre- or meta-mordanting procedures. In this experimental set-up, 42 different sample combinations are realized. Depending on type of dye and mordant, deep color shapes are achieved in the range of red, black to blue. By application of titanium mordant color shades are realized which are not covered by dyeing procedures using the other both mordants. Compared to the dyeing without mordant agent, the lightfastness increases clearly with the metal mordant application. This statement is especially valid for logwood dyeing which exhibits low light fastness grades of 1 or 2 without metal mordant. Depending on mordant procedure, dye/mordant combination and fabric, a light fastness in the range of grade 1–5 can be realized. Best values are determined with dye/copper mordant combinations leading to a light fastness of grade 5, which is an excellent value for natural dyes. In comparison, the determined light fastness from titanium containing applications are minor. Compared to the dyeing without mordant agent, the rubbing fastness decreases clearly with the metal mordant application. However, the application with titanium mordant is advantageous in rubbing fastness and with the combination of titanium/madder, a wet rubbing fastness grade 4 can be reached, which is an excellent result for a natural dye application. The actual study presents a broad range of dyeing recipes for natural dyes. Especially reported is the natural dyeing of Lyocell fiber materials and titanium mordant agents, which in that combination unique and up to now less considered in literature. Finally, the actual study is a helpful tool and starting point for future developments of natural dyeing of regenerated fibers as Lyocell in combination with metal mordanting agents.