Conventional Dyeing Process Research Articles

Mercerisation Followed by Wet on Wet Reactive Dyeing of Cotton Fabric

The commonly employed textile wet processing methods are singeing, de-sizing, scouring, bleaching, mercerising, dying, printing, and finishing. However, these methods are more time-consuming and require a lot of energy, manpower, and chemicals. Therefore, this research aims to develop a semi-continuous processing route that minimizes these problems. In this study, two dying routes were employed. The first is a control group, which was done by conventional mercerisation and dyeing procedures, whereas the second is a semi-continuous experimental group, which has been employed by mercerisation followed by wet-on-wet (WOW) reactive dying. That is, after mercerisation, the fabric, which contains the optimum alkali concentration, goes to dyeing without washing. Washing and titration were performed to determine the optimum alkaline concentration in the fabric at a specific washing cycle. Fabrics that were washed at different cycles after mercerisation were dyed, and their washing fastness, degree of dye exhaustion, fixation, and colour strength were evaluated, and they had a slightly greater colour strength than conventionally dyed fabrics. This is because with a wet-on-wet dyeing procedure, the fabric is relaxed after mercerisation, which allows it to absorb more dye, and the leftover alkali in the fabric is used to fix the dye to the cellulose. The study shows that the optimal washing cycle for passing the optimum alkali concentration is one. Furthermore, the optimal amount of alkali remaining in the fabrics is 3–3.5%. As compared to the conventional dyeing process, this process is economical.

Performance enhancement of reactive foam dyeing for cotton fabric through different foaming agents and stabilizers

Purpose In the textile dyeing industry, the foam dyeing has been recognized as a significantly sustainable alternative for the cotton fabrics. However, this efficient technology undergoes the many issues related to the foam generation, foam optimization and the required performance of the resultant fabrics. The purpose of this paper is to address these issues through the development and optimization of the novel reactive foam dyeing recipes for the cotton fabrics. Design/methodology/approach The foam dyeing recipes were generated and optimized using the different stabilizers, foaming agents and three primary colors of reactive dyes. The different recipes were applied onto the cotton fabric using laboratory scale foam coating machine. The performance of the foam coated and padded fabrics was evaluated using different criteria including the shade depth, rubbing fastness, air permeability, washing fastness, perspiration fastness, light fastness and tear strength. Then, a complex decision-making approach, namely, analytic hierarchy process (AHP), was applied for the ranking of the key recipes based on the main criteria. Findings The newly optimized foam dyeing recipes were found very competitive with the conventional pad dyeing process with respect to the shade-depth and the other performance properties. The optimization of foaming parameters and addition of stabilizers have advanced the foam dyeing process, which would accelerate the implementation of foam dyeing methods in the textile industry. Furthermore, significant water and energy savings would be achieved as compared to the conventional foam dyeing. AHP model offered a comprehensive and rational way to identify the most important recipes amongst the selected recipes. Originality/value In this research, novel foam dyeing recipes have been developed for the cotton fabrics through the optimization of the different stabilizers, foaming agents and the three primary colors of reactive dyes. Until now, the exiting literature has not reported the combination of these stabilizers with the different foaming agents and three primary reactive dyes for the improvement of sustainable foam cotton dyeing process.

Waterless Dyeing of Polyamide 6.6.

Waterless dyeing of polyamide 6.6 using scCO2 (supercritical carbon dioxide) was investigated. PA (polyamide) fibers can be dyed with various dyes, including disperse dyes. The conventional aqueous dyeing process uses large amounts of water and produces polluted water. Considering these environmental issues, waterless dyeing of fibers is a forefront issue, and utilization of supercritical carbon dioxide (scCO2) is a commercially viable technology for waterless dyeing. This study tested PA6.6 (polyamide 6.6) dyeing in scCO2 at 100 °C 220 bar pressure for 45 min. Color measurements and color fastness tests were performed, as well as tensile strength, scanning electron microscope (SEM) analysis, and Fourier transform infrared spectroscopy (FTIR) analysis. PA6.6 fabrics yielded higher K/S (color strength, the Kubelka-Munk equation) values with larger molecular weight dye and almost the same color strength with medium and small-sized dyes, demonstrating the ability of dyeing in a supercritical environment without water as a more environmentally friendly dyeing option compared to conventional dyeing.

Cleaner reactive dyeing with the recycled dyeing wastewater

In order to recycle water and inorganic salts, sodium persulphate (SPS) was used to degrade the C.I. Reactive Red 195 (RR195) dyeing wastewater. The thermodynamic and kinetic relationships of RR195 dyeing in cleaner and conventional dyeing processes were analyzed and compared. The feasibility of the one-bath cyclic dyeing in the recycled dyeing wastewater was confirmed through the properties of dye utilization, color parameters and energy conservation. The appropriate conditions were 0.3 g/L of SPS and treatment at 95 °C for 30 min, which resulted in a decolorization rate of 99.7% for the dyeing wastewater, mainly due to the action of radical sulfate. When cotton fabric was dyed with the cleaner dyeing, the kinetic was pseudo-second-order and the thermodynamic was Freundlich adsorption. There was a 47.5% reduction in half dyeing time, a greater diffusion coefficient and standard affinity, and lower entropy and enthalpy values when dyeing in reused wastewater. Cotton fabrics were dyed with the proposed cleaner dyeing process, which reduced the amount of water and inorganic salt by 95.8% and 89.8%, respectively. The total organic carbon (TOC), biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) were 53.6%, 69.8% and 42.6% lower than the conventional dyeing process, respectively. The recommended technology not only reduces the amount of dyeing wastewater but also enables the recycling of inorganic salts and water, which makes great progress in the textile industry.

An environmentally friendly indigo dyeing process using iron (II) gluconate as a reducing agent

This research paper aims to replace the ecologically harmful sodium dithionite traditionally used in the indigo dyeing process with the iron (II) gluconate reducing agent. The density functional theory (DFT) method using B3LYP 6- 311 G basis set was used to determine the optimized structures of iron (II) gluconate and indigo. The highest occupied molecular orbital (HOMO) energy and the lowest unoccupied molecular orbital (LUMO) energy were calculated, and the electronic properties dependent on HOMO-LUMO energies were determined. Furthermore, an ecological dyeing process using this reducing agent was studied. The influences of alkalinity, reduction temperature, and iron (II) gluconate concentration on the fulfilment of the dyeing process were inspected by measuring the obtained redox potential and the color strength of the dyed samples. A full factorial experiment was performed for statistical analysis and optimization of the dyeing process. The results revealed that the developed method is highly effective and capable of generating redox potential and dyeing quality comparable to those obtained with the conventional process employing sodium dithionite. Finally, the substitution of sodium dithionite by iron (II) gluconate reduced the wastewater load generated by the conventional dyeing process.

Regulating the hydroxyl groups reactivity of cellulose by grafting the quaternary ammonium group to achieve a salt-free and low alkali dyeing process for reactive dye

In this work, a salt-free and low alkali dyeing process was developed through cationic modification of cotton fabric with a series of quaternary ammonium salts (QAS). The dyeing performance indicated that the cationic cotton fabric treated with 3-chloro-2-hydroxypropyldimethyloctane ammonium chloride (CT-8) achieved better K/S value (8.87) and dye fixation (90.47 %) compared to the conventional dyeing process. Notably, the CT-8 treated fabric performed exceptionally under salt-free conditions and with a Na2CO3 concentration of 5 g/L. The rationale behind the adoption of a salt-free and low-alkali dyeing process was attributed to the positive charge of quaternary ammonium groups, which had an augmenting impact on the hydroxyl reaction activity of cotton fabrics. The condensed Fukui function, atomic charge, and HOMO orbital calculations showed that the QAS structure could regulate the hydroxyl reactivity of cationic cotton fabric. Our salt-free and low alkali dyeing process not only achieved the aim of reducing chemical consumption and emissions, but also contributed to better understand the effect of hydroxyl reactivity of cationic cotton on the fixation reaction with reactive dye, and provided a new direction to achieve the require of sustainable development and clean production for a variety of industrial crops and products.

Highly efficient cross-linking of reactive dyes in the amorphous zones of cotton fabric to simultaneously improve color and wrinkle properties

Dyeing and wrinkle-finishing of cotton fabric is generally achieved through two steps, which consumes a lot of energy and generates a lot of colored wastewaters. In this study, we report an energy-saving and cost-reducing dyeing process that enhanced the cross-linking degree of double reactive group dye in the amorphous zone of cotton fabric, which in turn improved the wrinkle resistance of cotton fabric as well as the utilization of the dye. Compared with the traditional dyeing processes, the method could improve K/S values by 69.7%, dye fixation by 22.4%, and wrinkle recovery angle by 21.5% for dyed cotton fabric. The wrinkle recovery angle of the dyed cotton fabric increased with the increase of cross-linking degree. The cross-section of cotton fibers changed from a flattened girdle shape to an elliptical or rounded shape, and the mid-cavity structure became smaller or even disappeared. In addition, the cross-linked structures could hinder the degradation of fiber macromolecular chains by cellulases. This meant that the better the wrinkle resistance of the dyed cotton fabric, the lower the glucose content in the degradation solution. Compared with the conventional dyeing processes, this dyeing method could be saved 36.5% of dyes and 28.4% of alkali for per 1 kg of cotton fabric, and the cost could be saved by 56.1%. The dye concentration in the waste water was reduced by 43.2%. This method had certain advantages in terms of economic and environmental.

INVESTIGATION INTO AN ECO-FRIENDLY REACTIVE DYEING PROCESS OF COTTON FABRICS USING AN ETHANOL-WATER MIXTURE THROUGH DESIGN OF EXPERIMENT

Textile industry professionals are unanimous that there is a great need to develop environmentally sustainable methods of cotton dyeing. Among various problems related to conventional dyeing, some of the main problems consist in the large volumes of discharge effluent with a high concentration of salt and their impact on the environment. This investigation explores the use of ethanol as a solvent in the reactive dyeing of cotton fabric, to reduce the concentration of salt and the volume of water used. The dyeing process employed a 90:10 (v/v) ethanol-water mixture. Time and temperature were varied periodically to improve the degree of exhaustion, and the effects of time, temperature and salt content were studied and compared with conventional reactive dyeing. It was observed that the colour strength of solvent-assisted reactive dyeing is comparable to the conventional process. The dyed sample under the optimum condition had good wash fastness, both in terms of shade change and staining, and its dry crocking fastnesses were found similar or acceptable in comparison with the water-dyed sample. However, all the samples of the solvent-assisted reactive dyeing process have better wet crocking fastnesses compared to the conventional reactive dyeing process. The process parameters of eco-friendly reactive dyeing have been optimised using the composite desirability function. The optimal process parameters for the solvent-assisted reactive dyeing process were found to be 60 minutes of dyeing at 80 °C with 20 g/L of salt.

Complete Desorption of Hybrid Nanoclays Composed of Hydrotalcite and Disperse Dye.

Clays are considered great nanoadsorbents for many materials, including textile dyes. The use of these materials for cleaning textile wastewater is well known; however, it is not at all common to find applications for the hybrid materials formed from the clay and dye. In this work, a dye-loaded clay material was used to make new dye baths and colour a polyester textile substrate. The same hybrid could be used several times as it did not use all the adsorbed dye in a single dyeing. The hybrid obtained from hydrotalcite (nanoclay) and the dispersed red 1 dye was analysed by measuring the colour obtained, carrying out an X-ray diffraction analysis that provided information after each desorption-dyeing process, and using infrared spectroscopy to analyse the specific bands of each characteristic group. Both analyses showed that the amount of dye present in the hybrid decreases. Thermogravimetry (TGA), surface area and porosity measurements (BET), and X-ray photoelectron spectroscopy (XPS) tests were conducted. Chemical stability was assessed by subjecting the hybrid to the actions of different reagents. In addition, colour fastness tests were carried out after dyeing and washing the polyester test tubes to check for the correct fixing of the dye to the fibre. These fastness results showed that the dyeing was carried out correctly and as if it was a conventional dyeing process.

Discussion on Factors Affecting Dyeing of Bio-based Polyamide 5,6 Fibers Compared with Polyamide 6,6 Fibers

To replace petroleum-based nylon and broaden the applications of polyamide 5,6 (PA56) in textiles, it is necessary to investigate the factors affecting the dyeing of bio-based PA56. In this work, bio-based PA56 and polyamide 6,6 (PA66) fibers were dyed with an acid dye. A comprehensive comparison of the factors affecting the dyeing performance of the PA56 and the PA66 fibers was carried out by measurements of the end-group content, crystallinity, and free volume fraction. The free volume fractions of the fibers in the dyeing process were calculated by the Williams-Landel-Ferry equation. Compared to the PA66 fibers, the results showed that the PA56 fibers had a better dyeing performance and water absorption behavior. Under the conventional dyeing process with water, the free volume fraction of PA56 fibers was slightly larger than that of the PA66 fibers. The larger the free volume, the more space for segmental motion and the easily entering of the dye into the interior of a fiber. The crystallinity of the PA56 fibers was 26.9%, which was lower than the 35.6% of the PA66 fibers. The lower crystallinity of the PA56 fibers means less regularity of macromolecular arrangement. The end-amino groups of the PA56 fibers and the PA66 fibers were 39.6 mmol/kg and 44.7 mmol/kg, respectively. Since the -NH2 groups only existed on the end of the polymer chains and the amount of -NH2 groups was low, the effect of the -NH2 groups content on the dyeing results was very small. Taking all these factors into consideration, the lower arrangement and the better segmental mobility of the molecular chains in the amorphous areas gave rise to the better dyeing performance of the PA56 fibers.

Interaction enhancement of Lyocell cellulose chains for controlled fibrillation behavior with greener application in eco-textiles

Lyocell is treated as a biodegradable, sustainable, and low-carbon emission cellulose fiber, but it possesses a high fibrillation tendency in the dyeing process which is generally conducted at alkaline, wet and high-temperature conditions. The fibrillation phenomenon seriously reduces the product quality and affects its application in eco-textiles. In response to the problem, a greener and simple fibrillation prevention treatment was innovatively conducted before the coloration process to enhance the interaction of Lyocell cellulose macromolecular chains. A nonionic crosslinker with isocyanate reactive groups was applied for the fibrillation control. The mechanism of the reaction between the nonionic crosslinker and Lyocell cellulose chains was determined through the measurements of fiber swelling, dynamic surface tension, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). It was found that the fibril interaction was significantly enhanced with reduced lateral swelling of Lyocell fibers. The fibrillation tendency was greatly reduced at the treatment condition of 20 g/L, 175 °C, and 80 s. Moreover, the interaction between cellulose chains was further improved after dyed with bifunctional reactive dyes. In comparison to commercial cationic and anionic crosslinkers, the nonionic sample not only showed little effect on the dye fixation, but also added good wrinkle resistance to Lyocell fabrics. The method showed the advantages of a shorter process and low chemical consumption compared to the conventional Lyocell dyeing process. Therefore, this work may promote the development of Lyocell fabric in high-quality and eco-friendly textiles.

Zero-water discharge and rapid natural dyeing of wool by plasma-assisted spray-dyeing

The application of plasma on textiles is a highly beneficial technique to improve dyeability and reduce the consumption of water, energy, and time. This is advantageous for the industries to demonstrate high productivity and quality of the product but at a lower cost. Plasma treatment usually is applied as a pre-treatment before the conventional dyeing process, where the generation of dye wastewater remains a challenge. Plasma post-treatment can make a huge difference in reducing the dye wastewater; however, this has received little attention and more specifically the effectiveness of plasma on natural dye fixation is unknown. Natural dyes from waste, such as onion skin (Allium cepa L.) are greatly abundant and a low-cost green option for sustainable dyeing of textiles. In this study, a clean method of dyeing wool fabric with onion skin is proposed using a plasma-assisted spray-dyeing technique with no wastewater discharge. Four different plasma parameters were used varying the plasma operating power (40 W and 64 W) and treatment duration (30 s and 60 s). Mordanting and dyeing were done by a successive spraying-drying method in multiple rounds to reach the identical shade of a parallelly conducted conventional dyeing process. The removal of the cuticle layer of wool by plasma treatment was perceived from the morphology of the treated fabric, possibly contributing to the wettability. A higher plasma operating power and longer treatment time were beneficial and affected the overall dyeability. The chemical structure of wool showed a higher hydroxyl peak intensity after dyeing and a lower peak intensity of C–H groups after plasma post-treatment. The colour fastness properties (washing and crocking) improved after plasma post-treatment and confirmed the possible attachment of unfixed dyes with fabric. Overall, the time and energy consumed by the plasma-assisted spray-dyeing technique was nearly one-third of conventional dyeing, with no wastewater generation and led to a better colour strength (20.4 compared to 15.8) and similar colour fastness. Results showed the great potential for this newly proposed method as a sustainable textile dyeing alternative.

Sustainable ultrasonic dyeing of unscoured and unbleached cotton sliver using low liquor ratio

The conventional dyeing process for cotton usually requires a high liquor ratio to achieve adequate dye migration and penetration to obtain uniform dyeing. However, a high liquor ratio increases water and chemical consumption, placing a heavy burden on dyeing effluent treatment. In this study, ultrasonic energy was used during the dyeing process to reduce the liquor ratio and improve the dye migration and exhaustion performance. The dyeing parameters, including liquor ratio, dyeing time, ultrasonic power, salt, and alkali concentration, were systematically studied. The dye uptake percentage, color strength, and CIE colorimetric values of the samples were examined, in addition to the scanning electron microscopic and optical images of the samples. The results show that the ultrasonic energy could facilitate the dyeing process by enhancing the diffusion and penetration of dye molecules, thereby ensuring uniform and thorough dyeing performance. The dye uptake percentage and color strength were improved by 120.0% and 25.6% when compared to the results of conventional dyeing process. The liquor ratio was significantly reduced to 6:1, and the high-energy consuming scouring and bleaching pretreatment processes normally required for conventional dyeing were avoided. Additionally, the dyeing time and consumption of alkali were also significantly decreased through the dye-promoting effect of ultrasonic energy, by more than 60.0% and 50.0%, respectively.

Sustainable silk dyeing in a silicon non-aqueous dyeing system with Reactive Red 195: salt-free and less alkali

Conventional dyeing processes usually generate a huge amount of wastewater, and in general, silk dyeing with reactive dyes using large amounts of salt and alkali has a great environmental impact. Herein, a green approach for a new dyeing system involving silk fabric dyed with reactive dyes in a silicon non-aqueous dyeing system without salt was reported. The optimal dyeing parameters of silk fabric dyed in this green dyeing system without alkali were 90°C for 75 minutes and with alkali were 70°C for 75 minutes, and the Reactive Red 195 exhibited good dye permeability, superior exhaustion, high fixation rate, and good dyeing depth, indicating the high utilization of dye and less effluent discharge. The color fastness of silk fabric dyed in the silicon non-aqueous dyeing system was comparable to silk fabric dyed in the conventional water bath. In addition, the fixation rate and K/ S value were improved by the addition of 0.4% (o.w.f) NaHCO3, which cannot be obtained in a conventional water bath, and all silk fabrics showed better tensile strength dyed in the green dyeing system. Therefore, the sustainable green dyeing method with a silicon non-aqueous system achieved a salt-free, less alkali or alkali-free, and simple process, which has the potential to solve the problems of wastewater, high salt, and high alkali in conventional dyeing processes.

Ecological Approaches to Textile Dyeing: A Review

Conventional dyeing processes currently practiced in the textile industry have a great environmental impact, mainly in relation to the quantity and pollution of water, use of toxic chemicals, atmospheric emissions, and high energy consumption. This study aims to discuss the relationship between the variables that involve conventional dyeing processes and environmental issues. It presents the mapping of the materials and emerging technologies for ecological coloration, specifically for the pretreatment and dyeing stages. Regarding pretreatment, it discusses biochemical (enzymes) and physical treatment (ultraviolet radiation, plasma, and ozone technology) approaches. With respect to the dyeing processes, it addresses ecological materials (natural dyes) and emerging technologies (such as plasma, supercritical CO2, AirDye®, ultrasonic, microwave, Nano-DyeTM, and electrochemical). Given the importance of ecological coloration, this study provides important reflections on the urgency of resolving issues related to barriers and economic viability in the implementation of the alternatives presented and demonstrates the need to develop educational projects to prepare fashion and textile professionals.

Toward improved performance of reactive dyeing on cotton fabric using process sensitivity analysis

PurposeThe conventional textile dyeing process requires various operational characteristics, and determining the most reliable factor in dyeing performance has always been a challenge for the textile industry. Thus, the present paper aimed to evaluate the process sensitivity of C. I. Reactive Blue 194 dyeing of cotton fabric using a statistical technique.Design/methodology/approach An L27 orthogonal array-based Taguchi's methodology was used with six parameters and three levels of each parameter. The signal-to-noise (S/N) ratio and analysis of variance were studied using total fixation efficiency (T%) as the response of the process sensitivity.Findings Results showed that dyebath pH was the most influential factor on the process and total fixation efficiency (p-value = 0.00 and contribution percentage 45.03%), followed by dye-fixing temperature, dye mass, electrolyte concentration, dye-fixing time and material to liquor ratio.Originality/value Overall this study provides a foundation for the determination of dyeing process sensitivity that will be useful in textile industries toward further development.

초정밀 가공을 이용한 다층 패턴 구조의 각도-독립적 구조색 구현

Structural color refers to a phenomenon, in which white light is influenced by the structure and the color is expressed. It can express various colors depending on the structures and has an advantage in terms of durability compared to the conventional dyeing processes. However, the structural color from a single layer easily varies depending on the light irradiation angle or measurement angle. Hence, numerous studies have been conducted to improve the angle-independency of structural color by fabricating multi-layers with complex nano-patterns. But, they usually require highly controlled processing environments and are not suitable for large-area manufacturing. Therefore, this study aims to develop a fabrication process by utilizing ultra-precision machining and silicon molding. Here, angle-independent structural colors were implemented with multi-layer micro-patterned films. Through the experiments, angle-independency was evaluated by varying the number of silicon films and measurement angles. RGB and HSV values were extracted from the images and applied for quantitative analysis. The suggested fabrication process successfully exhibited the angle-independent structural color with given patterns and film thickness. It is expected that this study can contribute to improving the multi-layer fabrication processes concerning machinability and large-area production.

Solvent assisted dyeing of wool fibers with reactive dyes in a ternary solvent system for protecting fibers against damage

Severe effluent pollution and chemical damage to protein fibers generated from conventional aqueous dyeing process have stimulated interest in exploiting sustainable dyeing of wool. Herein, an ethanol (EtOH)-carbon tetrachloride (CCl4)-water (H2O) ternary solvent system was used as the dyeing medium to protect wool fibers from being damaged in the dyeing process. The wool fibers were firstly pretreated in an aqueous acid solution, followed by dyeing in the EtOH-CCl4-H2O (45:50:5) ternary solvent system with reactive dyes. The results indicated that the acid pretreatment solution could be reused for several times, the samples dyed in the EtOH-CCl4-H2O mixture with the investigated dyes showed higher K/S values compared to the conventional approach, implying the increased dye utilization and decreased effluents discharge were realized. Furthermore, acceptable permeability, good colorfastness, and satisfactory leveling properties of the dyed samples were achieved using the developed method. Additionally, the solvent-assisted dyed samples showed improved mechanical properties compared with the conventionally dyed samples. The dyeing mechanisms of wool fibers in the EtOH-CCl4-H2O mixture were illustrated in detail. The proposed dyeing technology consumes fewer energy, freshwater, and chemicals compared with the conventional wool dyeing method. Future work will principally concentrate on the reuse of the dye-contaminated EtOH-CCl4-H2O mixture.

Combination of wet fixation and drying treatments to improve dye fixation onto spray-dyed cotton fabric

The conventional dyeing process requires a substantial amount of auxiliaries and water, which leaches hazardous colored effluents to the environment. Herein, a newly developed sustainable spray dyeing system has been proposed for cotton fabric in the presence of reactive dyes, which has the potential to minimize the textile dyeing industries environmental impact in terms of water consumption and save significant energy. The results suggest that fresh dye solution can be mixed with an alkali solution before spray dyeing to avoid the reactive dye hydrolysis phenomenon. After that, drying at 60–100 °C, wet fixation treating for 1–6 min, and combined treatments (wet fixation + drying) were sequentially investigated and then dye fixation percentages were around 63–65%, 52–70%, and above 80%, respectively. Following this, fixation conditions were optimized using L16 orthogonal designs, including wet fixation time, temperature, dye concentration, and pH with four levels where the “larger-the-better” function was selected to maximize the dye fixation rate. Additionally, the color uniformity and wash and rubbing fastnesses were at an acceptable level when both treatments were applied. Finally, the dyes were hydrolyzed after wet fixation, and the hydrolysis percentages were enhanced after the drying process.

β-Cyclodextrin: Disperse yellow 211 complexes improve coloristic intensity of polyamide dyed knits

Dyes are complex molecules that can sometimes cause damage to the aquatic environment and harm human health. They are often not completely removed from effluent by the usual treatments; therefore, efforts have been made to increase their exhaustion from dyeing through chemical and physical processes. In this context, the use of β-cyclodextrin (β-CD) as dyeing auxiliary agent promotes the reduction of harmful products, also increasing the color intensity of the fabric. In this paper, β-CD was used as a complexing agent to dye polyamide (PA) using the dye C.I. Disperse Yellow 211 (DY211) in order to improve dye exhaustion and color intensity using the β-CD:DY211 complex. The conventional dyeing process and β-CD:DY211 dyeing process by exhaustion were compared, and adsorption kinetics, isotherms, and the coloristic intensity were evaluated. The chemical shifts in the FTIR spectra and the thermal stability evidenced the formation of the β-CD:DY211 complex. Regarding dyeing kinetics and isotherm, the pseudo-first-order model was the most appropriate to describe the process, while Nernst isotherm was the one that best represented the adsorption results. Categorically, the samples dyed with the β-CD:DY211 complex obtained higher coloristic intensity in comparison with the conventional process. With this evidence, it is possible to conclude that cyclodextrin is a suitable replacement for environmentally harmful textile aides without adding further steps into the dyeing process or the need for additional equipment.