Sustainable multifunctional dyeing of nylon with Babool (Acacia nilotica) bark extract: Enhancing color metrics, fabric performance, UV protection, and antibacterial activity

There is an increasing demand for environment-friendly methods of textile coloration. On this basis, there is rising emphasis on biodegradable natural dyes. Natural dyes are perceived to provide functionality beyond mere appearance. This research investigates the multifaceted sustainable dyeing of nylon using the aqueous extract of Babool bark ( Acacia nilotica ). It has focused its attention on chromatic parameters, fabric properties, the UV protection factor, and antibacterial activity. The variables associated with the process of dyeing included time, temperature, pH, and Material: Liquor (M: L) ratio, which have been systematically optimized. Optimum conditions identified at 100 °C, pH 4.8, 60 minutes, and an M:L ratio of 1:30. In such conditions, nylon fabric showed improved coloration with greater K/S values, CIELAB color coordinates, and good shade repeatability. SEM studies revealed even deposition of tannins and natural colorants, while increased temperature resulted in increased fabric surface roughness and degradation due to thermal effects. The FTIR revealed good hydrogen bonding interactions between the dye and nylon polymer chains. The colored textile demonstrated good UV protection factor, which improved from 12.1 to 87.62 UPF values, meeting specific demands for high UV protective application in functional textile products for protective and healthcare apparel due to its phenolic compounds found in Babool bark. Even in the absence of diffusion inhibition zones, surface bacterial resistances were demonstrated in Bacillus spp. and P. pseudomonas . The dyed fabric has good color fastness properties to washing, perspiration, and rubbing tests, though light fastness was moderate, which in turn could be improved through effective mordanting process. Mechanical strength and air-permeability values also stayed within acceptable ranges. The result clearly indicates that Babool bark extract is considered to be an efficient and sustainable natural dye that is preferable for achieving appropriate textile coloration, effective UV protection, and good color fastness properties of dyed nylon fabric.