Sustainable dyeing of chemically modified cotton fabric with reactive dyes in acidic condition.

This study focuses on the improvement of the dyeability of cellulosic fibre with reactive dyes using a sustainable approach. A previously reported organic compound containing two epoxide rings, N¹, N^1'-(ethane-1,2-diyl) bis(N²-(oxiran-2-ylmethyl)ethane-1,2-diamine) (AXL-2) was employed as a cross-linker to the cotton fabric. AXL-2 was synthesized by reaction of epichlorohydrin (ECH) with triethylenetetramine (TETA). Reactive dyeing generates the most problematic effluent containing 20–50% dye in hydrolyzed form (due to the use of alkali in the dyeing process) along with large amounts of inorganic salts. Cotton fabric makes covalent interactions with AXL-2 that subsequently binds with the dye molecule containing free NH₂ or OH groups in acidic conditions rendering efficient dyeing in the absence of alkali and salts. ESI-mass spectrometry and ATR–FTIR spectroscopy were used to characterize the synthesized compound, while the treated cotton fabric was characterized by ATR–FTIR and SEM–EDX. Dyeing properties of AXL-2 treated cotton fabrics were studied by measuring their K/S values, % exhaustion, % fixation, and % total fixation. Color difference between treated and untreated fabrics (DE) was evaluated using CIE lab system that exhibited excellent color depth on the AXL-2 treated cotton fabric compared to pristine cotton fabric. Color fastness properties of the dyed fabrics were also studied. No significant change in the absorbency and thermal stability of the fabric was noticed after treatment. The tensile strength of the treated cotton fabric before dyeing (TC) was reduced by 7.6% in warp and 3.5% in weft directions as compared to untreated cotton fabric (CC). However, the treated cotton fabric had lesser reduction in the strength warp-wise compared to untreated cotton fabric after dyeing along with an increase in the strength weft-wise. The novel dyeing method of treated cellulosic fibre by reactive dyes renders a sustainable and eco-friendly approach. [ABSTRACT FROM AUTHOR]