Research in the International Journal of Materials and Product Technology describes a metal-free dye-fixing process that could help make natural plant dyes more practical for high-performance textiles, addressing a longstanding obstacle to their wider use in sustainable clothing.
Natural plant dyes are biodegradable and generally produce less pollution than synthetic dyes, but they fade easily when worn, washed or exposed to light. This has limited their use in functional textiles, antibacterial fabrics or those that help repel biting insects.
The new method replaces the conventional metal salts, or mordants, used to bind dye molecules to fibers. Mordants are major contaminants of wastewater from the textile dyeing sector. The new fixation system is based on a modified form of chitosan, a biopolymer derived from natural sources such as crustacean shells, and ellagic acid, which is found in many plants.
The dyes are held in place through electrostatic attraction between electrically charged molecules and hydrogen bonding, a chemical interaction that helps stabilize the dye without permanently altering the fabric. The researchers also optimized dyeing conditions—including temperature, acidity and steam treatment—to improve dye uptake while preserving the fabric's functional properties.
In tests on antibacterial fabrics, they showed that around 70% of the dye remained on the fabric even after 25 washes, with water- and light-fastness remaining high even after many hours of exposure. Antibacterial performance remained above 90% after repeated washing.
More information
Jiaheng Han et al, Colour fixation process and colour fastness improvement strategies for natural plant dyes in functional clothing fabrics, International Journal of Materials and Product Technology (2026). DOI: 10.1504/ijmpt.2026.155354
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Citation: Metal-free process makes plant dyes more durable for textiles (2026, August 4) retrieved 5 August 2026 from https://phys.org/news/2026-08-metal-free-dyes-durable-textiles.html
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