Metal-free process makes plant dyes more durable for textiles

Scientists have developed a metal-free process that enhances the durability of plant-based dyes for textiles, addressing a key challenge in using natural dyes for sustainable clothing. Natural dyes, which are biodegradable and less polluting than synthetic alternatives, fade easily when exposed to wear, washing, or light. This limitation has restricted their application in functional textiles, antibacterial fabrics, or insect-repellent clothing.

The innovative method replaces traditional metal salts, known as mordants, which contaminate textile wastewater, with a modified form of chitosan, derived from crustacean shells, and ellagic acid, a plant-derived compound. The process relies on electrostatic attraction between charged dye molecules and hydrogen bonding, a chemical interaction that stabilizes the dye on fibers without permanently altering the fabric's properties.

Researchers fine-tuned dyeing conditions, such as temperature, acidity, and steam treatment, to enhance dye uptake while maintaining the fabric's functional attributes. In trials on antibacterial fabrics, the dye retained around 70% after 25 washes, with excellent water- and light-fastness, and antibacterial properties remained above 90% even after repeated washing.

The study, published in the International Journal of Materials and Product Technology, demonstrates that this metal-free fixation system effectively preserves plant dyes on textiles, improving their durability for various functional applications.