Sustainable Dyeing of Nylon 6 Fabric with Turmeric (Curcuma longa) Extract Using an Infrared-Assisted Exhaust Process

The present study focuses on the dyeing of knitted polyamide (nylon 6) fabric using turmeric (Curcuma longa), a natural dye source, through an infrared (IR)-assisted dyeing technique without the use of mordants and chemical auxiliaries. In this process, a 1% (w/v) aqueous turmeric dye extract was prepared and then applied on nylon 6 fabric through an IR-assisted exhaust dyeing method under different dyeing conditions, including variations in liquor ratio, dyeing time and temperature. The dyed samples were investigated for color strength (K/S), colorimetric properties (L*, a*, b*, ΔE*), surface morphology by scanning electron microscopy (SEM), elemental analysis by energy dispersive spectroscopy (EDS), antibacterial activities, antioxidant analysis and colorfastness (washing, light, and rubbing) properties according to standard testing protocols. The maximum K/S of 31.03 was observed under optimized conditions such as a liquor ratio of 1:30, a dyeing temperature of 110 °C, and a dyeing time of 60 min. The improved color strength was observed under optimized conditions such as a moderate temperature, a lower time and a high liquor ratio. SEM analysis revealed successful dyeing of nylon 6 without damaging the fiber surface morphology. The dyed samples showed good to excellent colorfastness properties, including rubbing (4–5), washing (4–5) and light fastness (5–6). The dyed fabrics also exhibited antibacterial activity against both Staphylococcus aureus (up to 87.46% reduction) and Escherichia coli (up to 79.08% reduction), and antioxidant activity of up to 75.15% in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. Thus, the IR-assisted dyeing process for nylon fabric is a promising dyeing method to dye synthetic textile fabric using natural colorant without the use of dyeing auxiliaries.