Cationic starch (Q-TAC) pre-treatment of cotton fabric: influence on dyeing with reactive dye.

Reactive dyes require high concentrations of an electrolyte to improve dye-fiber interaction, leading to the discharge of harmful effluent. One approach to reduce this unsafe release is treatment of the cotton fabric with cationic chemical reagents. This paper reports on the treatment of cotton fabric with cationic starch (Q-TAC), a commercial product, by batchwise method and pad batch method for the first time prior to reactive dyeing process. Furthermore,three commercial reactive dyes, based on monochloro triazine, vinyl sulfone and monochlorotriazine + vinyl sulfonechemistry, was applied on the cotton fabrics by continuous (pad-dry-cure) method. The treated cotton fabric by batchwise method produced 70% higher color yield (K/S) and 20% enhanced dye fixation (%F) than the untreated cotton fabric. X-ray photoelectron spectrometer (XPS) analysis revealed the presence of N1s peaks in the treated cotton fabrics. The crystallinity of treated cotton fabrics was reduced in comparison to untreated cotton fabric as revealed by wide angle X-ray diffraction (WAXD) measurements. Field Emission Scanning Electron Microscopy (FE-SEM) showed that the surface of treated cotton fabrics was rougher than untreated cotton fabric due to the deposition of cationic starch. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrum confirmed the existence of quaternary ammonium groups, N(+)(CH3)3, in the treated cotton fabrics. The analysis of color fastness tests demonstrated good to excellent ratings for treated cotton fabrics. In this way, cationic starch treatment of cotton fabric before reactive dyeing process has been proven potentially a more environmentally sustainable method than conventional dyeing method.