Optimization of dyeing process parameters for bioactive cotton and silk fabrics with Racinus communis leaf extract 

Woven cotton and silk fabric samples have been dyed with Racinus communis extract at optimized conditions of extract concentration, temperature, material - to - liquor ratio (MLR), alum concentration and treatment time, and then evaluated for their fastness properties following ISO standards, antimicrobial activity quantitatively against Staphylococcus aureus and Pseudomonas aeruginosa bacterial strains and wash durability. Central composite design and single-factor design have been used in the optimization process, and based on the lowest number of colony-forming units per milliliter, optimized values are selected. The results indicate that optimized extract concentration of 39%, dyeing temperature of 70ºC, alum concentration of 3g/L, MLR of 1:30 (silk) and 1:40 (cotton), and treatment time of 30min (silk) and 40min (cotton) lead to 99.84% and 99.78% bacterial count reduction against Staphylococcus aureus and Pseudomonas aeruginosa respectively for dyed cotton fabrics. However, for dyed silk fabrics, a more improved percentage reduction in the bacterial count of 99.88% and 99.83% respectively is realized against both bacterial strains. Retention of the antimicrobial activity of dyed fabrics is found to be more significant even after 5 washes. The fastness properties of rubbing, washing, light, and perspiration for both fabrics range from moderate to excellent.