Salt-free reactive dyeing of betaine-modified cationic cotton fabrics with enhanced dye fixation

Novel cationic cotton fabrics were prepared by an efficient and simple one-step pad–dry–bake pretreatment process with betaine as cationic reagent. Ester bonds formed between cotton fibers and betaine hydrochloride were proved by Fourier transformed infrared attenuated total reflection(FTIR-ATR) spectra. Moreover, the properties of the cationic fabrics, including X-ray Diffraction(XRD), tensile strength and whiteness and yellowness index,were investigated in comparison with that of the untreated ones. The cationic fabrics were applied in salt-free dyeing of C.I. Reactive Red 195, C.I. Reactive Yellow 145 and C.I. Reactive Blue 19. Different dye fixation processes were applied and compared for untreated and cationic cotton. Dye fixation and color fastness properties of the dyes were tested, and the results presented that dye fixation on the cationic fabrics in the absence of salt was improved with satisfactory light fastness property and applicable wash and rub fastnesses.