Explore the vast range of titles available.

Cotton fabric is usually dyed with reactive dyes. During the dyeing process, a large amount of salt is required to achieve higher exhaustion of the dye from the dyebath onto the fiber. Dyeing of cotton with reactive dyes has a substantial environmental impact due to the discharge of a large volume of highly colored and saline effluents. Chemical cationization allows cotton fibers to be dyed without salt by chemically modifying cellulosic macromolecules to introduce positively charged sites. In this study, cotton fabric was cationized using (3-chloro-2-hydroxylpropyl) trimethyl-ammonium chloride (CHPTAC). Dye uptake was assessed using two reactive dyes, CI Reactive Blue 235 and CI Reactive Blue 19. Dye exhaustion kinetics were determined using a Datacolor-HueMetrix Monitor system. Analysis of variance demonstrated significant effects of CHPTAC concentration and exhaustion time on the percent exhaustion. Color strength at the end of the dyeing cycle was significantly higher for cationized fabrics compared to the control fabric. This work shows that treatment of cotton with CHPTAC enhanced dye uptake properties due to the introduction of cationic sites and resulted in superior dyeing without the addition of salt.

A real anhydrous liquid ammonia dyeing technique was established that included a cationic modification of the ramie fiber in liquid ammonia, dyeing of the cationic ramie fiber in liquid ammonia, drying to fix the cationic agents and the reactive dyes in the ramie fiber, and washing the cationic ramie fiber and the dyed cationic ramie fiber with liquid ammonia to remove the unfixed chemicals. The zeta potential of the cationic ramie fiber indicated that the cationic groups were successfully grafted on the fiber. The dye exhaustion percentage and the fixation rate improved. The dyed cationic ramie fiber had excellent wash fastness, satisfactory color uniformity, and acceptable breaking strength and breaking elongation rate for spinning. High performance liquid chromatography analysis was used to measure the stability of the dye’s reactive group during the liquid ammonia dyeing and drying. The results showed that the dichlorotriazinyl group was unstable, while the monochlorotriazinyl and vinyl sulfone groups were stable during the liquid ammonia dyeing. The monochlorotriazinyl group and vinyl sulfone groups changed to their non reactive derivatives after drying. Graphic abstract

Reactive dyes maintain a long reaction with fiber and show a high dye uptake and fixation rate, and effectively decrease the dyeing waste water in siloxane reverse micro-emulsion. However, little research has been carried out into the hydrolysis reaction of reactive dyes in reverse micro-emulsion. In this study, Reactive Blue 19 was selected as a model vinyl sulfone reactive dye to study its hydrolysis in siloxane reverse micro-emulsion. The hydrolysis reaction was analyzed using high performance liquid chromatography. The results show that the hydrolysis rate of vinyl sulfone dyes in siloxane reverse micro-emulsion was slower than that in a traditional bath. Influences due to the ratio of aqueous dye solution to siloxane, non-ionic surfactant, cellulose fiber, and temperature on the hydrolysis reaction of vinyl sulfone reactive dye were also researched. The results show that with more aqueous solution emulsified in the siloxane media, the hydrolysis reaction of vinyl sulfone dye is faster. Reactive dyes were emulsified into a water micro-environment with non-ionic surfactant, which formed reverse micro-emulsion, and decreased the content of free water; this further influenced the hydrolysis of reactive dye.

Since it does not use any dangerous chemicals and is a simple, low-cost process, the green synthesis approach for nanoparticle creation has several benefits compared to the physical and chemical synthesis routes. The current study describes an environmentally friendly synthesis of zinc oxide (ZnO) nanoparticles (NPs) using an extract of Punica granatum plant leaves. Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible spectrophotometer (UV-Vis), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy, and X-ray diffraction techniques were used to characterize the morphology, composition, and structural properties of the synthesized zinc oxide nanoparticles. The XRD pattern reveals that the ZnO nanoparticles are crystalline and have a diameter of 20 nm. According to the FESEM studies, the ZnO-NPs have sizes ranging from 50 to 100 nm on average and are almost spherical. When exposed to direct sunlight, the produced ZnO-NPs demonstrate impressive photocatalytic oxidation of textile Orange 16, a reactive dye. As a result, our research advances the development of a green photocatalyst for the removal of harmful dyes from water.

A potentially environmentally responsible dyeing procedure for ultra-deep shades on cotton was developed using a cationization method in combination with mercerization. The effects of both treatments on dyeing performance and colorfastness properties of cotton fabrics dyed with reactive dyes were analyzed individually and in combination. Both mercerization and cationization have been proved to be effective in increasing the depth of shade on cotton. The colorfastness properties, except colorfastness to wet crocking, of mercerized–cationized cotton fabrics dyed without salt were much better than untreated cotton dyed using a conventional dyeing procedure. Unlike untreated cotton fabrics, the concentration of Na₂CO₃ in the dyeing process of mercerized–cationized cotton fabrics was lowered from 20 to 5 g/L without compromising dye fixation and colorfastness properties. With low concentrations of dyes and Na₂CO₃ and no electrolyte in the dye bath effluent, the dyeing procedure of mercerized–cationized cotton fabrics for ultra-deep shades is potentially a more environmentally benign method than conventional dyeing with reactive dyes.

Three novel vinyl sulfone reactive dyes of various metallic salts (Na, K, Li) have been synthesized by coupling 1-amino-phenyl-4-beta hydroxyethyl sulfone sulfate ester with 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid (H-acid). The reactive dyes were then purified using ultrafiltration (UF). The ultrafiltrated dyes of the various metallic salts were characterized by their spectrophotometrical data using Ultra Violet-visible (UV-vis), Fourier transform infra-red and optical emission spectroscopy, X-ray diffraction, and elemental analysis. The purity of the dyes was checked by Thin Layer Chromatography (TLC). The solubility characteristics of the various salts of the ultrafiltrated reactive dyes were assessed and compared with the non-ultrafiltrated reactive dyes of the same salts. The dyes were characterized and applied to cotton, wool, and nylon 66 by exhaustion (dyeing). Novel water-based reactive ink-jet inks were prepared with the ultrafiltrated reactive dyes of the various metallic salts. Their suitability for digital printing applications was examined by using a digital printer on suitably pretreated cotton samples. Color and fastness properties measurements were performed for both the dyed and digitally printed samples. K/S values of the dyed samples were higher than those of the digitally printed ones, whereas K/S values of the samples dyed with the ultrafiltrated dyes were much higher than those of the non-ultrafiltrated dyes. The other coloristic co-ordinates L*, a*, b*, C*, and ho were in line with strength changes of the dyes before and after UF. The dyed and digitally printed samples had excellent wash and good light fastness properties. UF slightly improved the fastness properties of the dyed samples.

The chemical recycling of cellulosic fibres may represent a next-generation fibre–fibre recycling system for cotton textiles, though remaining challenges include how to accommodate fibre blends, dyes, wrinkle-free finishes, and other impurities from finishing. These challenges may disrupt the regeneration process steps and reduce the fibre quality. This study examines the impact on regenerated viscose fibre properties of a novel alkaline/acid bleaching sequence to strip reactive dyes and dimethyloldihydroxyethyleneureas (DMDHEU) wrinkle-free finish from cotton textiles. Potentially, such a bleaching sequence could advantageously be integrated into the viscose process, reducing the costs and environmental impact of the product. The study investigates the spinning performance and mechanical properties (e.g., tenacity and elongation) of the regenerated viscose fibres. The alkaline/acid bleaching sequence was found to strip the reactive dye and DMDHEU wrinkle-free finish from the cotton fabric, so the resulting pulp could successfully be spun into viscose fibres, though the mechanical properties of these fibres were worse than those of commercial viscose fibres. This study finds that reactive dyes and DMDHEU wrinkle-free finish affect the viscose dope quality and the regeneration performance. The results might lead to progress in overcoming quality challenges in cellulosic chemical recycling.

Structural changes in mercerized cotton by liquid ammonia (LA) treatment were investigated and correlated with changes in dyeability of cotton fabrics with reactive dyes. The pore structures of mercerized cotton and mercerized-liquid ammonia (M-LA) treated cotton were characterized by inverse size exclusion chromatography (ISEC). Results showed that when the mercerized cotton was subjected to LA treatment, cumulative accessible volume of smaller pores (e.g., 25.2 Å) increased, whereas that of the larger pores (e.g., 56.7 Å) decreased. These results might be related to the changes in the amorphous region of cotton fiber. The decrease in crystallinity of cotton fiber would increase accessible volume of smaller pores. The larger pores might be compressed by extrusion during swelling of microfibrils or elementary fibrils in water. The change in dyeability of fabrics with reactive dyes of various molecular weights could be rationalized using the observed changes in pore structure. Results also showed that ISEC was more suitable than the method employing Chrastil's diffusion equation for analyzing the pore structure of cotton fiber.

Hydrolysis of reactive dyes is a well-recognised phenomenon that significantly affects dye fixation, chemical consumption, and effluent load in textile dyeing processes. Several advanced analytical techniques—such as ¹H-NMR, capillary electrophoresis, and high-performance liquid chromatography (HPLC)—have been developed to quantify this process. However, the complexity and resource-intensive nature of these methods limit their routine and widespread application. In this study, a simplified fixation-based method is proposed to estimate reactive dye hydrolysis. The method estimates dye hydrolysis based on the fixation percentage of pre-hydrolysed dye relative to a reference sample. Reactive dye hydrolysis was carried out at 60 °C for 60 min, with analysis conducted at 20-min intervals. A monofunctional reactive dye, Remazol Yellow RR, was used as a model compound, and the maximum hydrolysis determined by the proposed method was 61.6%. The same samples were also analysed by HPLC, which indicated that 80.5% of the dye had undergone hydrolysis under the same conditions. Although the fixation-based method reports lower hydrolysis values than HPLC, a strong linear correlation was observed between the two approaches, indicating that the proposed method can reliably capture relative changes in dye hydrolysis under the studied conditions. Furthermore, kinetic analysis demonstrated that the hydrolysis reaction follows a pseudo-first-order model. The proposed fixation-based method, therefore, offers a practical pathway for dyehouses to independently assess reactive dye hydrolysis behaviour using routine dyeing and spectrophotometric measurements. Future studies involving a broader range of reactive dyes, reactive systems, and dyeing conditions will be necessary to further evaluate the robustness and broader applicability of the proposed approach in practical dyehouse settings.

Chemical cationization of cotton has been a subject of increased interest due to the ability of cationized cotton to attract negatively charged dyes, thus eliminating the use of electrolytes during dyeing and increasing color yield. However, electrostatic attractions between cationized cotton and anionic dyes also result in significantly increased dye strike rates, which may cause levelness problems, especially when light to medium shades are required. In this study, cotton fabric cationized using 3-chloro-2-hydroxypropyl trimethylammonium chloride was used to investigate the method for obtaining appropriate dye strike rate to produce a level reactive dyeing on cationized cotton. To effectively control the dyeing kinetics of reactive dyes on cationized cotton, real-time exhaustion of six commercially significant reactive dyes were monitored. The influence of temperature, dye structure, and addition of soda ash on dyeing kinetics and levelness of cationized cotton were evaluated.