Synthesis and application of a coumarin-derived dye for sustainable dyeing of polyester fabric

Purpose This study aims to synthesize a coumarin-derived dye and evaluate its application in polyester fabric dyeing, focusing on its potential as a safer alternative to hazardous disperse dyes. By examining the dye’s fastness, fluorescence, thermal behavior and theoretical binding interactions, this research supports more sustainable practices in textile processing. Design/methodology/approach The coumarin dye, 7-diethylamino-3-acetylcoumarin, was synthesized via the Knoevenagel reaction. Polyester fabrics were dyed using this coumarin dye under various conditions, including acidic and alkaline. Dyeing performance was evaluated based on washing, rubbing and light fastness tests, with particular attention to reductive washing for optimal results. The dye’s structural characteristics were analyzed through Fourier transform infrared spectroscopy (FTIR), ultraviolet––visible (UV–Vis) and nuclear magnetic resonance (NMR) spectroscopy. Thermogravimetric analysis assessed thermal stability and degradation behavior. Density functional theory simulations were conducted to elucidate dye–fiber interaction mechanisms at the molecular level. In addition, in vitro cytotoxicity was tested using human skin fibroblast (CCD-1079Sk) cells. Findings The coumarin-derived dye exhibited excellent dye affinity and colorfastness on polyester fabrics, especially in acidic conditions with a 45-minute dyeing process followed by reductive washing. No cytotoxic effects were observed in human skin fibroblast cells, underscoring its potential as a safer alternative to conventional synthetic dyes. UV–Vis spectroscopy confirmed strong absorption properties, making the dye suitable for various textile applications. Research limitations/implications The study focused on polyester fabric; future research should extend the application to other textile types. Moreover, further investigation into aquatic degradation pathways and industrial-scale applicability is needed to fully validate environmental benefits. Practical implications The findings suggest that coumarin-derived dyes could provide a safer and more environmentally friendly alternative to disperse dyes in the textile industry. The successful application of the dye under both acidic and alkaline conditions makes it versatile for use in polyester dyeing, potentially reducing chemical waste and health risks associated with synthetic dyes. Originality/value This study contributes to the growing body of research on sustainable textile dyeing by demonstrating the potential of a coumarin-derived dye for polyester fabrics. Its fluorescence, non-toxic nature, robust fastness properties, eco-friendliness and adaptability to different dyeing conditions make it a valuable alternative to traditional hazardous dyes, supporting the shift toward greener practices in the textile industry.