Dyebath pH Research Articles

Dyeing behaviour of iron(III)-gallic acid complexes on wool as function of pH-dependent iron(III)-complex stoichiometry

Iron complexes with polyphenolics e.g. gallotannins and flavonoids have been used since ancient times for coloration of textiles, painting and preparation of inks. The composition of iron gall inks on historical artefacts has been investigated with modern instrumental methods. However the dyeing behaviour of iron-complexes with polyphenols still bases on empirical knowledge. In this study Fe(III)-complexes with gallic acid were used as model system to elucidate their pH dependent sorption and dyeing behaviour on wool. At dyebath pH 3 high sorption of Fe(III)-gallic acid complexes was observed, however darker dyeings were obtained at dyebath pH 4. Model calculations for the complex species present in the dyebath indicated the presence of the binary complex [Fe(III)(GA2−)]+ as main species at pH 3, while at pH 4 the ternary species [Fe(III)(GA2−)2]- prevails. The dye sorption bases on Van-der-Waals forces, while ionic interactions between Fe(III)-complex and keratin are of minor relevance. The elaborated theoretical model also explains the influence of dyebath pH in dyeing with gallotannins, polyphenols and flavonoids in presence of iron salts and thus is of particular relevance for improved utilisation of these natural colorants.

A Study of Color Fixation Agents in Secondary Alcohol Ethoxylate-Based Reverse Micellar Cotton Dyeing System with Reactive Dyes

ABSTRACT Influence of color fixation agent (CFA) and dyebath pH in secondary alcohol ethoxylate (SAE)-based reverse micellar dyeing system of cotton with reactive dyes was investigated and compared with water-based dyeing system using different alkali (i.e. CFA) such as: (i) sodium bicarbonate (NaHCO3), (ii) sodium carbonate (Na2CO3) and (iii) sodium hydroxide (NaOH). The color, tensile strength, fastness and surface morphological properties of dyed samples were examined. Experimental results showed that samples dyed with Na2CO3 can achieve the highest color yield, followed by NaHCO3 and NaOH in both water-based and reverse micellar dyeing system. The color yield and reflectance percentage of the dyed cotton samples were found to be closely related to the dyebath pH value. Relative unlevelness indices (RUI) also reflected that cotton samples dyed with NaOH in reverse micellar dyeing system have a higher chance of color unlevelness when compared with NaHCO3 and Na2CO3. Tensile strength results affirm that higher alkalinity of dyebath could cause higher strength loss to the colored cotton samples. Both cotton samples dyed by water and SAE approach showed good to excellent color fastness properties while scanning electron microscopic (SEM) images exhibit that the use of different alkalis may cause some damage to the cotton fiber.

Adsorption kinetics and thermodynamics of metal complex acid dyes on silk fabric

This study reports the adsorption phenomena of metal complex acid dyes onto silk fabric. Two commercial metal complex acid dyes namely Bestalan Yellow SF and Bestalan Navy SF were adsorbed onto degummed silk fabric. The functional properties and surface morphology of silk fabric were investigated with FT-IR spectroscopy and FE-SEM respectively. The typical absorption band of C = O stretching was found at 1620 cm−1 indicating amide I structure and C-N stretching as well as N-H bending vibrations were observed at 1510 cm−1 suggesting the β-sheet crystallites of amide I and amide II silk proteins. The effectiveness of degumming performance was confirmed by SEM images. The adsorption of dyes by silk fabric was investigated with respect to pH, initial dye bath concentration, and contact time. It was found that the adsorption of dye onto silk fabric was highly influenced by the dye bath pH, initial dye concentration, and contact time. The higher dye adsorption was observed at acidic dye bath condition (pH = 3.5). The adsorption of dye was also increased with the increase of the initial dye bath concentration. The dyes adsorption reached at equilibrium condition after 80 min. The adsorption isotherm and kinetics were also evaluated based on the experimental results. The adsorption pattern fitted well to the Langmuir adsorption isotherm with high correlation coefficient (R 2>0.97) for both dyes. The kinetic parameters suggested that the pseudo-second-order model is more suitable compare to the pseudo-first-order model considering the higher regression coefficients ( R 2 = ∼ 0.99 ) . The maximum adsorption of Bestalan Yellow SF and Bestalan Navy SF was found to be 232.5 and 222.2 mg/g respectively. The thermodynamic data were studied at 25, 40 and 60 °C. The change of Gibbs free energy of the system was positive indicating the spontaneous nature of the adsorption. The values of ΔH (-4.68 kJ/mole −3.65 kJ/mole) suggested the exothermic environment and the negative values of ΔS (-0.035 and −0.034 kJ/mole/k) advocated the good interaction between the metal complex acid dyes and silk fabric. The Langmuir adsorption model and pseudo-second-order kinetic suggested that the dyeing of metal complex acid dyes on silk fabric was controlled by ion-exchange chemical reaction.

Over dyeing of Lyocell fabric with natural indigo and rhubarb

In order to enrich the range of natural dye chromatography, this study used rhubarb to dye indigo dyed Lyocell fabric to obtain green Lyocell fabric. Firstly, the Lyocell fabric was dyed with indigo using a typical reduction method. The K/S and b* values of dyed fabrics were used as evaluation indicators to determine indigo concentration of 1.2 g/l before the over dyeing. The effects of rhubarb concentration, pH value, and dyeing temperature on the K/S value and color characteristic value of rhubarb dyed Lyocell fabric are discussed. The results showed that acidic solution, higher rhubarb concentration, and lower dyeing temperature were beneficial to obtain higher K/S and b* values for the rhubarb dyed Lyocell. Finally, these three factors were taken as independent variables in over dyeing, and the red-green value of dyed fabric was taken as response value for response surface analysis. The response surface analysis of three factors and three levels showed that the pH value of the dye solution had a significant impact on the a* value. The a* value of the dyed fabric decreased with the increase in rhubarb concentration and the decrease in the pH value and dyeing temperature. The optimization process suggested by the regression model statistical analysis was as follows: rhubarb concentration was 2.67 g/l, dye bath pH 3.5, and dyeing temperature 57°C. The verification result showed that a* value of the over dyed fabric was –10.75, which was close to the predicted value –10.98. The infrared results showed that the cellulose characteristic groups of the undyed and dyed Lyocell fabrics were almost same. The Lyocell fabric dyed with indigo and rhubarb showed a blue-green color, and 50+ ultraviolet protection factor. The washing color fastness of the over dyed Lyocell fabric was 2–3 and the rubbing fastness was above 3. This over dyeing method may enrich the chromatogram of Lyocell fabric dyed with natural dyes.

Sustainable Dyeing Process for Nylon 6 Fabrics by Rhubarb Flower Using Different Bio-Mordants

The purpose of this study is to propose a fully sustainable dyeing process for nylon 6. In order to achieve this goal, Rhubarb flower parts were used to produce a brown hue on nylon 6 fabric. The effects of dyeing parameters such as dyeing time, temperature, dyebath pH, M:L, salt addition, dispersing agent, and dye concentration on color strength were investigated. Using 100%owf dye in an acidic medium at boil and the material to liquor ratio of 1:30 for 75 min was determined to be the optimal condition for dyeing nylon 6 with rhubarb flower. In order to achieve acceptable color fastness, four natural mordants were applied, including walnut husks, pistachio hulls, pine cones, and green coffee. Colorimetric measurements revealed that mordanting did not affect the hue of the color compared to the non-mordant sample. In addition, diverse natural mordants produced the same color (i.e., brown) with varying color strengths, of which 10%owf walnut husk generated the strongest color. Bio-mordanted samples were also found to have excellent color fastness, thereby providing an effective substitute for metal mordants.

The Influence of pH of Float on the Dyeability of Polyester Fabric

Disperse dyes are essentially non – ionic, exhibit poor solubility in water, and they can be used in the form of water dispersion. Polyester fibres are resistant to dilute aqueous acids and alkaline solutions and pH value does not provide a crucial impact on the dyeing mechanism; however, many disperse dyes undergo degradation if the pH is uncontrolled during aqueous dyeing. In order to minimize the possibility of dye hydrolysis, the dyeing is carried out in a slightly acidic medium, and pH is usually adjusted with acetic acid. In this work, the quantity of disperse dyes (Sinten Gelb P-5GL and Sinten Scharlach P-3GL) applied to polyester knitwear was investigated as a function of pH. The sorption capacity of polyester knitwear was monitored by using reflection curves and CIELab system, according to Swiss software Sandoz (based on spectrophotometry). The acetic acid was used for dyebath pH adjustment. The results showed that the maximum uptake of Sinten Gelb P-5GL and SintenScharlach P-3GL dyes by polyester knitwear occurred at pH 4.64 (0.2924%) and 6.20 (0.1860%), respectively. According to reflection curves in the range (max = 400-700 nm), the effect of pH on the sorption of Sinten Gelb P-5GL was more significant than one for Sinten Scharlach P-3GL, when concentration of dye is constant (0.4%). The CIELab values for three illuminants (daylight, light – bulb and incandescent) showed a significant dependence between pH float and hue and intensity of polyester knitwear dyeing with disperse dyes

Pomegranate fallen leaves as a source of natural dye for mordant‐free dyeing of wool

AbstractThe application of metal mordants is usually necessary in dyeing of wool with natural dyes to improve the dye exhaustion and fastness properties. The majority of metal salts generally used as mordants are considered as toxic and it is important to find replacements for them. Plant sources with high content of tannins are good candidates as bio‐mordant or colourant to overcome this drawback. In this study, the waste fallen leaves of pomegranate tree were used as a source of natural dye for the eco‐friendly dyeing of wool fabric without the use of metal mordants. The dyeing process variables including dye concentration, dyebath pH, and temperature were optimised using response surface methodology to obtain the highest colour strength. The colour strength was increased by increasing the natural dye powder up to 100%owf while the optimum pH and dyebath temperature were 4 and 100°C, respectively. The sample dyed under the optimal condition exhibited good fastness properties against washing and light. This study approved the potential of Punica granatum fallen leaves for the dyeing of wool without any mordant, while high fastness properties were obtained.

Effect of dye bath pH in dyeing of cotton knitted fabric with reactive dye (Remazol Yellow RR) in exhaust method: impact on color strength, chromatic values and fastness properties

The significance of textile coloration is inevitable as coloration is a critical process and it can be affected by several parameters i. e. time, temperature, pH, and liquor ratio (M:L). This research reveals the behavior of different dye bath pH (2 to 12) on the basis of spectrophotometric characteristics and colorfastness using the most useable brand of reactive dye in Bangladesh i. e. Remazol Yellow RR. Earlier researches were performed on the basis of other coloration controlling factors i. e. temperature, time and liquor ratio (M:L) where pH acts as the dependent variable. However in this study, pH was taken as an independent variable where lower pH (2, 4 and 6), medium pH (8 and 10) and higher pH (12) were taken into consideration for verifying the dyeing performance. Meanwhile, the mentioned pH was achieved by adding acetic acid, soda ash and caustic soda respectively. In this study, the impact of pH is analyzed on the basis of color strength, chromaticity, hue angle, CIELAB color space, spectrophotometric image, reflectance percentage and color fastness tests i. e color fastness to rubbing, color fastness to wash, color fastness to perspiration, color fastness to light. Gradually elevated pH boosts up the color strength and chromaticity, at the same time downgrades of hue angle results orangish tone in the dyed fabric. Even more, the lightness of dyed fabric decreases and redness rises with the increment of dyebath pH which results in orangish red darker tone of dyed fabric. Consequently, fabric dyed at acidic dye bath pH exhibits higher resistance in case of color change and color staining from the dyed fabric and multifiber fabric respectively and vice versa.

Exploring Chitosan as an Ecofriendly Agent to Improve Sustainable Dyeing Properties of Cotton Fabric Dyed with (Opuntia Ficus-Indica L) Fruit Peel and Its UV Protection Activity

ABSTRACT This paper explores the use of Chitosan as sustainable agent to improve dyeing properties of cotton fabric dyed with Opuntia ficus-indica L fruit peel and the determination of the amount of anthocyanin pigments by the spectrophotometric method. The results of this study highlights that cotton fabrics treated with chitosan have better depth of shade (K/S = 12) than those untreated fabrics (K/S = 3.7) dyed with Opuntia ficus-indica L fruit peel. We have thoroughly investigated the effects of dye bath pH and temperature on the color properties of the aforementioned fabrics. UV protection of cotton fabrics increased after natural dyeing, and it was further improved after being treated with chitosan. Experimental results show that the fastness properties of dyed cotton fabrics treated with chitosan were improved from average to excellent.

Sustainable Dyeing and Functionalization of Different Fibers Using Orange Peel Extract's Antioxidants.

A diluted ethanol orange peel extract was used for sustainable dyeing and functionalization of different fabrics. The extract analysis was performed using UPLC-ESI-MS/MS; its total flavonoid (0.67 g RE/100 g d.w.) and antioxidant (2.81 g GAE/100 g d.w.) contents and antioxidant activity (IC50 of 65.5 µg/mL) were also determined. The extract dyeing performance at various dyebath pH values was evaluated using multifiber fabric. Among six fabrics, extract possessed the ability for dyeing wool, polyamide, and cellulose acetate (at pH 4.5), which color strength (K/S) values increased after washing (9.7–19.8 vs. 11.6–23.2). Extract:water ratio of 20:35 (v/v) was found to be sufficient for achieving satisfactory K/S values (i.e., 20.17, 12.56, and 10.38 for wool, polyamide, and cellulose acetate, respectively) that were slightly changed after washing. The optimal dyeing temperatures for wool, polyamide, and cellulose acetate are 55, 35, and 25 °C, while the equilibrium dye exhaustion at those temperatures was achieved after 45, 120, and 90 min, respectively. The color coordinate measurements revealed that wool and polyamide fabrics are yellower than cellulose acetate, while, compared to polyamide and cellulose acetate, wool is redder. Possible interactions between selected fabrics and extract compounds are suggested. All fabrics possessed excellent antioxidant activity (88.6–99.6%) both before and after washing. Cellulose acetate provided maximum bacterial reduction (99.99%) for Escherichia coli, and Staphylococcus aureus, which in the case of Staphylococcus aureus remained unchanged after washing. Orange peel extract could be used for simultaneous dyeing and functionalization of wool and polyamide (excellent antioxidant activity) and cellulose acetate (excellent antioxidant and antibacterial activity) fabrics.

Application of response surface methodology(RSM) on comparative analysis of senegalia catechu dye in different mordanting conditions on cotton fabric

ABSTRACT In this research work, cotton fabrics were dyed through Senegalia Catechu dye in two different mordants conditions such as myrobalan and pomegranate rind power. Three process parameters were taken, such as dyeing temperature, dye bath pH, and mordant concentration for optimization, and other processing conditions were kept unchanged. The Box-Behnken-L15 experimental design was followed for experimentation. Regression models were generated for two different mordanting conditions, and their statistical significance was also verified through ANOVA. A comparative analysis between two mordant conditions was done through RSM analysis and found that shade variations between the two different mordanted samples were noticeable in most cases. The FTIR and SEM analysis on the dyed fabric was carried out to understand the dyeing effectiveness and chemical modification of the structure. The optimized process parameters of myrobalan mordant condition are pH level (6–7), maximum dyeing temperature (80°C), and maximum mordant concentration (25%-30%). The optimized process parameters of pomegranate rind power are pH level (9–10), moderate dyeing temperature (70°C), and maximum mordant concentration (25%-30%). These differences were interpreted due to the chemical nature of mordants, dyeing condition, raw material specification etc.

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.

Evaluation of Color Properties of Wool Fabrics Dyed with Calligonum comosum at Different Dye Conditions

In this search, the wool fabric was dyed with a natural dye Calligonum comosum (Callig. Co. dye); the dyeing process was applied under different conditions by changing dye bath temperature, time of dyeing, and pH of dye bath also using different mordants. Ultraviolet protection factor (UPF) was determined for each dyed wool sample. The role of these dying conditions on the via color strength analysis their effects on the reflectance spectra were investigated using the spectro-photometer tool, CIE tristimulus values, and the color parameters. The dye-ability strength and fastness to washing and perspiration properties of these wool samples dyed with (Callig. Co. dye) were carried out spectrophotometrically and evaluated the antimicrobial activity for blank and dyed wool fabrics via gram-positive and gram-negative was followed. The results showed that dyeing wool fabrics with (Callig. Co. dye) increased their protective abilities markedly, and they have effective protection against UV rays, also improving their antimicrobial activity. Moreover, Different conditions of the dye bath changed the optical properties noticeably. The present study will be useful for dermatologists advising patients regarding the UPF properties of clothes made from natural fabrics (wool) and dyed with natural colorants (Callig. Co. dye).

Eco-friendly antibacterial dyeing of poly(lactic acid) with prodigiosins suspension produced by Zooshikella ganghwensis

Dyeing poly(lactic acid) (PLA) fiber with natural dyestuffs has attracted a lot of attentions due to the production of the fully eco-friendly textile products. In this study, PLA nonwoven fabric was successfully dyed using microbial prodigiosins as clean disperse dyestuff. Prodigiosins suspension with the mean size 243.6 nm was prepared by the fermentation of Zooshikella ganghwensis in the presence of nonionic surfactant. Meanwhile, the dyeing process to endow PLA nonwoven fabric with purplish red color as well as antibacterial performance was investigated in detail. The results indicated that the PLA nonwoven fabric exhibited good color strength, low strength loss, good bacteriostatic properties against Staphylococcus aureus when it was dyed under dyebath pH of 4–5 at 90 °C for 20 min. Additionally, the dyed PLA nonwoven fabrics showed excellent rubbing fastness and washing fastness. Overall, a clean dyeing process using microbial prodigiosins from renewable sources as functional disperse dyestuff for PLA nonwoven fabric is developed, which is beneficial to realize the further green production of PLA nonwoven fabric.

Mordant-free dyeing of nylon fabric with mahogany (Swietenia mahagoni) seed pods: A cleaner approach of synthetic fabric coloration

The extraction and consequent application of natural colorants obtained from mahogany ( Swietenia mahagoni) seed pod powder is described here. The colored solution was extracted by facile boiling in an acidic medium. Fourier-transform infrared spectroscopy indicated that the mahogany seed pod extract contained lignocellulosic substances. The typical strong broad band for -OH stretching vibration appeared at around the 3400 cm−1 region in the spectra indicating the presence of alcoholic groups in the substance. The acidic boiling of the mahogany seed pod extract showed the color bearing character at λmax 400–480 nm in the visible range of the ultra-violet spectrum. Subsequently, commercial single jersey-knitted nylon fabric was dyed with the mahogany seed pod extract. The effects of temperature, pH, and time were investigated meticulously for the above dyeing. The optimum conditions for nylon fabric dyeing with the mahogany seed pod extract were selected as the temperature of 100°C, dyeing time of 60 min, and dyebath pH 4.5. The results were interpreted in terms of color strength and fastness properties. The color fastness to wash and perspiration of nylon fabric dyed with mahogany seed pod extract was found to be moderate to good in the grey scale rating 3–4 to 4 grade in the case of optimum dyeing condition whereas color fastness to light was observed to be poor in the blue wool scale rating 2 grade. It was observed that dyeing time, temperature, and pH had profound influences on the color strength of the dyed material. The color strength was increased with the increase of dyeing period and dyebath temperature. The acidic dye liquor produced the darker hues while the alkaline condition had no effect on color yielding. The fabric was dyed uniformly, confirming the evenness of dyeing which is very important for successful commercial dyeing.

Study of the Dyeing Properties of Annatto and Ultrafiltrated Annatto as Colourants for Natural Fibres

ABSTRACT Cotton and wool fabrics have been dyed in the absence of mordants with annatto and ultrafiltrated annatto powder. Τhe optimum dyeing conditions were determined as far as the quantity of salt and dyebath pH are concerned. The dyeing properties of annatto and ultrafiltrated annatto were studied by monitoring the dye uptake in various time intervals and temperatures of dyeing. The adsorption isotherms for both annatto and ultrafiltrated annatto were studied. It was found that adsorption of annatto on cotton follows a BET-type adsorption isotherm indicating a multilayer formation of molecules onto cotton, whereas the adsorption of ultrafiltrated annatto follows a Freundlich-type monolayer adsorption. Adsorption of both annatto and ultrafiltrated annatto on cotton occurs through the formation of Van der Waals forces between annatto molecules and cotton substrate. The adsorption on wool of both annatto and ultrafiltrated annatto follows a Freudlich-type adsorption isotherm indicating a monolayer formation occurring between the positively-charged wool substrate and the negatively-charged annatto molecules. The dyeing behavior of natural annatto resembles that of the synthetic direct and acid dyes commonly applied for dyeing cotton and wool. Thus, annatto and ultrafiltrated annatto can successfully replace the synthetic yellow dye component in the dyeing of cotton and wool fibers.

Ecofriendly application of coconut coir (Cocos nucifera) extract for silk dyeing.

The worldwide resurgence of natural dyes in all fields is due to the carcinogenic effects of effluent loads shed by synthetic industries. Coconut coir (Cocos nucifera) containing tannin as a source of natural colorants has been selected for coloration of bio-mordanted silk under the influence of ultrasonic radiations at various dyeing conditions. For extraction of tannin dye from cocos powder, different media were employed, and dyeing variables such as dyeing time, dye bath pH, dyeing bath temperature, and the effect of salts on dyeing were optimized. For achieving new shades with excellent color characteristics, bio-mordants in comparison with chemical mordants were employed. It has been found that acid-solubilized extract after ultrasonic treatment for 45 min has yielded high color strength, when coconut coir extract of 4 pH from 6g of cocos powder, containing 5g/100mL salt solution as exhaust agent, was used to dye silk at 75°C for 65 min. Among bio-mordants turmeric (K/S=13.828) and among chemical mordants iron has shown excellent results (K/S=2.0856). Physiochemical analysis of fabric before and after US treatment shows that there is no change in the chemical structure of the fabric. It is found that ultrasonic waves have excellent potential to isolate the colorant followed by dyeing and environmental friendly mordanting at optimal conditions, but also the usage of herbal-based plant anchors, i.e., bio-mordants, has made the natural dyeing process more sustainable and clean.

Dyeing and printing study of synthesized reactive dyes using phenyl urea bifunctional reactive dyes on cotton fabric

Reactive dyes have verity of Shades and have a good all fastnesses properties. Bifunctional reactive dyes were mostly popular in Dyeing and Printing industries. Three Bifunctional reactive dyes was synthesized and this dyes applied on Cotton fabric with Dyeing and Printing Method. Cold Pad-Batch and Exhaust dyeing method was used for application of Dyeing… Dyes were characterized by absorbance spectra, IR and 1H NMR. The main object of study was to get maximum strength as well as good fastness properties of Synthesized dyes on Cotton fabrics. Different parameters for Dyeing like Time of Dyeing, pH of Dye bath and Concentration of Alkali were study. From the study it was observed that All dyes gave good fixation on 100%cotton fabric and also gave good absorbance above 60% results with printing method. The all dyes have good fixation on cotton by Cold Pad-Batch dyeing method Synthesized Bifunctional reactive dyes had excellent fastness properties.

New class of magenta dyestuffs based on azomethine pyrazolone disperse dyes: Synthesis, characterization, and dyeing performance on polyester fabrics with ultraviolet protection and pH-dependent properties

Eight azomethine pyrazolone magenta dyes with iminodiethanol groups have been synthesized from 1,3-disubstituted- 1H-pyrazol-5( 4H)-ones in good yield. The newly synthesized dyes were characterized using spectroscopic data and elemental analyses techniques. All dyes have been successfully applied to polyester fabrics as disperse dyes where their dyeing performances have been discussed and evaluated in detail. The shades of these dyes ranged from red violet, purple and dark purple colors with good depth, brightness and good leveling properties. Multifunctional properties such as color representation, colorimetric data (L*, a*, b*, C*, h*, K/S), fastness properties of the dyed samples with respect to washing, perspiration, rubbing and light fastness have been discussed and evaluated in detail. The degree of exhaustion and fixation was also achieved after establishing the optimal dyeing conditions at 130°C, high pressure, 2% shade, and pH ≈5. As well, the influence of the dye bath pH on the K/S percentage and color intensity was estimated and discussed. Furthermore, the dyed fabrics were tested for ultraviolet protection factor and the results showed that these dyes gave excellent ultraviolet protection.

Optimization of dyeing process variables for eco-friendly dyeing of cotton fabric with babul bark extract as a natural dye and gallnut extract as a bio-mordant

ABSTRACT In the present study, cotton fabric has been dyed with aqueous extract of babul bark (Acacia nilotica) using gallnut (Quercus infectoria) as bio-mordant containing hydrolyzable tannins like gallic acid, elagic acid and polyphenolic gallotannins to produce light yellow color. On the other hand when gallnut bio-mordanted cotton is subsequently dyed with babul bark extract as a natural dye containing similar but non-hydrolyzable tannin-rich color component including small amount of catechin and epi-gallo-catechin, it produces a medium to deep brown color through formation of giant insoluble colored complex of cotton-gallotannins (gallnut)-catechin/epigallocatechin and other color components present in babul bark extract. The process variables for extraction, pre-mordanting and dyeing have been optimized to standardize this dyeing technique. Scattered CDI values for dye-bath pH and dye concentration identified them as the most important dyeing parameters that need to be controlled for obtaining uniform dyeing. High UPF value of upto 35 rendered by application of both gallnut and babul bark through preferential absorption of UV light by the gallotannins in both gallnut and babul bark indicates good UV protection properties of dyed cotton fabrics.