Multifunctional Dyeing Process and Characterization of Silk Fabric Based on Natural Colorant of Rhubarb

To promote the application of natural dyes in eco-textiles and develop multifunctional silk fabrics, this study optimized the extraction of functional pigments from rhubarb and investigated their dyeing performance and functional properties on silk. The optimal extraction conditions were determined as pH 11, 80 °C, 50 min, with three extraction stages. The optimized direct dyeing parameters for silk fabrics were: dye bath pH value of 7, bath ratio of 1:40, dye solution concentration of 5%, and dyeing at 80 °C for 60 min. Post-dyeing metal ion mordanting significantly regulated the hue and dyeing depth of fabrics, with ferrous sulfate mordanting demonstrating the most ideal effect, enabling fabrics to exhibit deep gray coloration and a substantial increase in K/S value. The dyed silk exhibited significantly enhanced Ultraviolet (UV) protection (UPF 18.72 for direct dyeing, reaching 29.80 after Fe²⁺ mordanting) and antibacterial activity (inhibition rates of 69.26% and 77.49% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively, exceeding 95% after Fe²⁺ treatment). This work demonstrates that rhubarb dyeing can produce functional silk with excellent UV-blocking and antibacterial properties, supporting its potential in ecological textiles.