An alternative natural dye,almond shell waste: effects of plasma and mordants on dyeing properties

In this study, the effect of the plasma process and the possibility of replacing metallic mordants with plasma treatment were investigated in natural dyeing with almond shell waste as a novel natural colorant. The use of a smaller amount of metallic mordants and plant than most of the current natural dye applications is a major advantage of dyeing with almond shell extract. Plasma‐treated and untreated wool fabrics were dyed without mordant and using a smaller amount (0.2 g/l) of alum, iron(ii ) sulfate and copper(ii ) sulfate. Three mordanting methods, namely premordanting, simultaneous mordanting and post‐mordanting, were applied. Colour measurements and light and wash fastness values were compared. Significant colour differences were observed among the mordanting methods. Simultaneous mordanting resulted in the lightest colours with all the mordants. Generally, post‐mordanting produced duller colours and lower a* and b* values than premordanting. The plasma process generated significant colour value differences and colour yield increases, giving more homogeneous dyeing visually, and also ensured a greater impact of mordanting. However, compared with metallic mordants, plasma itself did not create completely different colour shades and fastness improvement. It was necessary to use mordants in order to achieve increased fastness properties (especially light fastness) and a different colour gamut.     

An innovative approach to the preparation of coloured and multifunctional silk material with the natural extracts from chestnut shell and black rice bran

In order to reutilise the byproducts of foods and crops to benefit the environment and economise on resources, the natural extracts from chestnut shell and black rice bran were applied in the simultaneous dyeing and multifunctionalisation of silk fabrics. In this work, the influence of pH value on dyeing properties was studied. The effects of the ratio of chestnut shell and black rice bran extracts and the application of mordants (aluminium potassium sulphate and ferrous sulphate) on the dyeing performance as well as anti-ultraviolet and antioxidant properties of treated silk were also discussed. The results showed that deep-coloured silk fabrics can be obtained when dyed with the two natural extracts as the pH value of the dyebath approached 3. The ratio of the two natural extracts and the use of the mordants have significant effects on colour depth, colour hue, colour fastness, and the functionalities of dyed silk fabrics. Combination dyeing and mordanting are able to enrich the colour hues of dyed fabrics. The washing, rubbing, and light fastness of the dyed fabrics after mordanting can be rated higher than grade 4. Moreover, the silk after combination dyeing has good UV protection performance (UPF > 30) and antioxidant activity. In addition, the functionalities of treated fabrics showed excellent washing fastness. This study reveals that chestnut shell and black rice bran extracts are suitable as natural colourants and multifunctional finishing agents for the preparation of coloured and multifunctional silk materials.     

Application of rare earth as mordant for the dyeing of ramie fabrics with natural dyes

Selecting appropriate metallic compounds as mordants is essential for dyeing with natural dyes. This paper presents the application of rare earth compounds as mordant for the dyeing of ramie fabrics with four kinds of natural dyes. The influences of pre-mordanting, simultaneous mordanting, and post-mordanting on the dyeing effect were explored. The post-mordanting was proved to give rise to the highest dye uptake. The effects of dyeing conditions including dyeing temperature and time, dyeing bath pH and the concentration of rare earth on the dye uptake were investigated systematically. The fabrics dyed with natural dyes in presence of rare earth as mordant exhibited high color shade stability in the baths with pH varying from being acidic to neutral and alkaline. Employing rare earth as mordant apparently raised the color fastness to washing, rubbing and light of the ramie fabrics dyed with the natural extracts. In comparison with the commonly used metallic salts, using rare earth chlorides as mordants can greatly reduce the ionic concentration employed in natural dyeing. This study proved that rare earth would be a kind or promising environmentally friendly mordant in natural dyeing.     

A route from olive oil production to natural dyeing: valorisation of prina (crude olive cake) as a novel dye source

An attempt has been made to valorise an agroindustrial solid waste in natural textile dyeing as a novel dye source. The dyeing and fastness properties of prina (crude olive cake/pomace) extract were evaluated to fill the gap in this field. This very cheap biomass was utilised (80 g/l) by applying chemical solvent‐free aqueous extraction to dye wool fabric with only small amounts (0.2, 0.4, 0.8, and 1.6 g/l) of metallic mordants, namely alum, iron(II) sulfate, copper(II) sulfate, stannous chloride, and potassium dichromate, and avoiding the use of alkali, acid, chemicals, and auxiliaries in dyeing and washing processes. Colour shades of beige, cream, sandy, apricot, straw, cumin, mustard, olive, and khaki were obtained. Significant differences in colour strength and CIELab coordinates were observed, depending on mordant type and mordanting method. Copper(II) sulfate and iron(II) sulfate ensured the most significant colour changes and nuances, the darkest colours, and the best light fastness values. Prina extract itself (without mordant) has a light fastness of 3 (fair) and excellent wash fastness of 4–5, both for colour change and bleeding. Irrespective of the concentration and mordanting method, alum, stannous chloride, and potassium dichromate did not generate a light fastness improvement compared with the control sample. Although good light and wash fastness values have been achieved without mordants, it is necessary to use them to widen the colour gamut and to obtain increased colour strength.     

Metal ion effect on dyeing of wool fabric with catechu

Wool fabric was dyed with catechu by two different process sequences using various metal sulphates as mordant. The dyeing behaviour has been assessed by measuring K/S values and different fastness properties. The effect of different metal ions have been studied with respect to their influence on colour and fastness properties. The mechanism of mordant interaction with the fibre has been briefly considered.     

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

The 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.     

核桃青皮醇提物对棉织物染色性能的研究

为解决天然染料核桃青皮染色色调单一的问题,以颜色特征值和染色牢度为指标,通过单因素和正交实验优化了影响染色效果的温度、时间、pH值及核桃青皮色素染液的质量浓度等因素,比较了单金属盐的不同媒染方法和双金属盐复配对纯棉织物染色性能的影响。结果表明,核桃青皮色素染色的优化条件为：温度90oC、质量浓度71.40 g/L、染浴pH=4.0、时间140 min。核桃青皮提取液染色棉织物色谱的范围广,耐摩擦牢度好;耐皂洗牢度上单金属盐媒染是后媒＞前媒＞同浴＞直接染色,双金属盐复配及Fe3+、Fe2+、Cu2+、Al3+、Cr6+等单金属盐媒染的耐皂洗色牢度均能达到3级以上。X-射线衍射分析表明棉织物内部结构未受影响,Fe3+、Fe2+、Cr6+、Sr2+、Na+和K+等单金属盐和Fe2+/Cu2+、Fe2+/Ti4+、Cu2+/Ti4+、Cu2+/Sn2+、Al3+/Cr6+、Cr6+/Ti4+和Cr6+/Sn2+等双金属盐媒染后的棉织物紫外线防护能力增强。     

Assessment of the dyeing properties of pigments from five fungi and anti‐bacterial activity of dyed cotton fabric and leather

The present study was aimed to assess the anti‐bacterial activity and dyeing property of the pigments obtained from five fungal species. Cotton fabric and leather samples were dyed with the purified pigments and their anti‐bacterial activity was assayed under in‐vitro conditions. Post‐mordant cotton fabric and leather samples exhibited maximum bacterial reduction when compared with the pre‐mordant and dyed samples. Pigment exhaustion, colour coordinates and fastness properties of the dyed cotton fabric and leather samples were also assessed. The toxicity of the pigments was evaluated by seed germination assay.     

Evaluation of antimicrobial and dyeing properties of walnut (Juglans regia L.) green husk extract for cosmetics

Walnut green husk is one of the main waste products from walnut and could be used as a source of natural dyeing compounds such as juglone. The present study was conducted to evaluate the effective use of walnut green husk extract as a natural hair dye. Dyeing properties, fastness and antimicrobial behaviours of dyed hair and also a skin irritation test for natural hair dye on rat skin were examined. When the extract was mixed with ascorbic acid as a developer, ferrous sulphate as a mordant, and Aloe vera extract used as a secondary mordant and also a cosmetic ingredient, the reaction resulted in a dark‐brown colour on hair samples. The dyed hair exhibited appropriate colour strength having excellent morphology for a hair surface coated with dye molecules. In addition, the dyed hair possessed good resistance to washing and daylight fastness, without any irritant properties as shown in a rat model, although high concentrations of iron‐based mordant may be problematic for long‐term usage. This paper also suggests the use of natural mordants such as lactic and oxalic acids to avoid any probable risks. Walnut green husk extract was an appropriate natural hair dyeing agent in practice and showed maximum antimicrobial activity compared with semi‐synthetic and commercial hair dyes. The results demonstrated that walnut green husk can be used as an economical, valuable, eco‐friendly and safe source of dyeing and antimicrobial agents for cosmetic products.     

Effects of additives on the dyeing of cotton yarn with the aqueous extract of Combretum latifolium Blume stems

Flavonoid constituents from the aqueous extract of the stems of Combretum latifolium Blume sourced in Thailand have potential use as dyestuffs for cotton dyeing. In an effort to improve current natural dyeing methods with this extract, further aspects of the process were studied. It was found that, before equilibrium was reached, an increase in temperature led to an increase in dye adsorption rate of the extract; the initial rate and extent of dye adsorption was further increased by the addition of sodium chloride to the dyebath. In addition, cotton yarn pretreated with a chitosan solution (with and without a crosslinking glyoxal solution), followed by dyeing with C. latifolium extract, provided better depth of shade and also gave better fastness to light and washing than the untreated cotton yarn. Post‐mordanting cotton yarn with a biomordant solution from Memecylon scutellatum leaves also gave good light and wash fastness of the resulting dyed cotton, comparable with the dyeing results with the less environmentally friendly alum as a mordant.     

A method for dyeing cotton fabric with anthocyanin dyes extracted from mulberry (Morus rubra) fruits

For the first time, the natural anthocyanin dyes (mainly consisting of cyanidine 3‐glycoside) extracted from mulberry (Morus rubra) fruits has been successfully used to dye cotton fabric, with a dyeing property performance good enough for potential commercial applications. In this study, succinic acid was firstly incorporated into cotton fabrics by esterification to the hydroxyl groups of cellulose, forming an anionic site for the dyes. The performance of the modified material was characterised by Fourier transform infrared spectroscopy and tensile strength. Results showed that the tensile strength of cotton fabrics was mostly retained after modification. The anthocyanin extracts from mulberry fruits were used to study the dyeability of the control and modified cotton fabrics. Red and deep purple (aubergine) are two main shades of cotton fabrics dyed with mulberry fruit extracts. Most importantly, aubergine shade is rare in cotton fabrics dyed with natural dyes. Modification with succinic acid clearly increased the colour strength of the dyed cotton fabric. The colour strength of dyed cotton fabric was improved from 2.7 to 5.3 in the case of dyeing without mordants, and from 3.2 to 6.9 in the case of dyeing with tin mordanting. Meanwhile, the colour fastness was improved by 0.5–2 grades with increasing succinic acid concentration in the finish solution. The colour fastness to perspiration, crocking, light, and washing of fabric dyed with simultaneous tin mordanting and modified with 30 g l^?1 of succinic acid was found to be acceptable, with a grey scale grade of at least 3. As for home laundering, neutral soapy solution was more acceptable than alkaline soapy solution.     

Isolation of colour components from flowers of Tabebuia argentea: kinetic and adsorption studies on silk yarn

The colour components from the flowers of Tabebuia argentea have been isolated and characterised as rutin and epigallocatechin gallate using spectral techniques. Adsorption kinetic and thermodynamic studies of these colour components on silk yarn have been investigated. It is noted that the adsorption is an endothermic process. The dyeing studies have been carried out at pH 4. The mordanting studies revealed that the post‐mordanting technique could only increase the dye performance marginally. The fastness properties of the dyed silk were determined. The adsorption isotherm studies showed that the Langmuir model fitted the experimental data very well with a high regression coefficient.     

Eco‐friendly pretreatment of silk fabric for dyeing with Delonix regia extract

The flowers of Delonix regia have been evaluated for the natural dyeing of silk using a biomordant and enzymes. This is an eco‐friendly textile pretreatment that does not utilise metal mordanting. The aqueous extract obtained from the dried red flowers was used for the dyeing of silk fabrics. A bright reddish‐brown hue colour was observed when 30% owf Delonix extract was used on the pretreated silk material. The silk fabric was treated with either an enzyme or biomordant. The resulting dyed fabric showed resistance to fading. Finally, all dyed specimens were tested for wash and light fastness properties, making Delonix a viable alternative to synthetic red dyes. Through desorption studies, the order of reactivity of enzymes towards dye uptake in the one‐step process was found to be lipase > diasterase > protease–amylase = Pyrus(biomordant). For the two‐step process, the order of reactivity of enzymes was found to be protease–amylase > lipase > Pyrus (biomordant) > diasterase. Overall, it can be concluded that, treatments, the two‐step process was better in terms of larger colour yield values, fastness properties and both dye adherence ability.     

Colour and fastness of natural dyes: revival of traditional dyeing techniques

Cotton and wool fabrics were dyed with nine natural dyes obtained by aqueous extraction of the original plants/insect in an attempt to reconstruct traditional textile dyeing recipes, to optimise the methodology at all stages, i.e. extraction, mordanting and dyeing, and to standardise it. Cochineal, madder, alkanna, henna, brazilwood, red sandalwood, safflower, indigo and logwood were used for the dyeings, which were carried out directly and after mordanting of the textile material. A variety of mordants, namely, aluminium potassium sulphate, potassium dichromate, copper sulphate, zinc chloride, iron(iii ) chloride, iron(ii ) sulphate and tin chloride, is anticipated to meet both early and recent requirements and options. The dyeings were evaluated through colour measurements and standard wash, light and rub fastness tests. Generally, the mordanting process known for many centuries and connected with the textile dyeing resulted in an improvement in dye absorption and fastness properties mainly for the cotton samples, as is concluded from the tests and measurement assessments.     

Cotton fabric dyeing with cochineal extract: influence of mordant concentration

Dyeing with cochineal extract has been carried out in Mexico since pre‐Hispanic times as a handcraft process. However, this has limited its application on fabrics other than wool. An experiment was designed to study the influence of mordant concentration on colour behaviour in cotton fabric dyed with cochineal extract at the laboratory. At the same time, colour fastness was determined by applying six fastness tests to define the quality of the dyed fabric. It was concluded that, when there was a larger concentration of metallic ions in the mordant, colour fixation in the fabric was better, as there was less lightness in the red hue of the fabric. In addition, the more hydrogen ions present because of acids, the more intense the red hue. A decreasing trend in the colour fastness tests was observed: dry rubbing > artificial light > acids > alkalis > domestic washing > hot water.     

Digital and conventional printing and dyeing with the natural dye annatto: optimisation and standardisation processes to meet future demands

The plant colorant annatto was investigated to determine its potential use as a natural dye for conventional and novel textile applications. Alum was selected as a mordant. Different techniques of mordanting and a broad set of variations in the dyeing recipes were applied to achieve optimisation and an improvement in colour fastness properties. Quality control of all dyeings was performed using standard fastness tests and colour measurements. Printing of cotton fabrics was also achieved with annatto using the flatbed screen‐printing technique. Measurement of the rheological and physical properties of the annatto printing paste confirmed its stability and suitability for conventional printing. Fastness properties of the conventionally printed annatto fabric were also measured. A novel water‐based digital printing ink using annatto was prepared and applied to cotton fabric using a digital printing application. The physical properties of the annatto ink‐jet ink were also measured. Wash, light and rub fastness properties of the annatto digitally printed fabric were determined and compared with those of conventional printing methods. The results were promising for annatto as a natural colorant, which possibly paves the way for the development of a new range of natural environmentally friendly dyes.     

Polydopamine‐coated silk yarn for improving the light fastness of natural dyes

One of the problems occasionally associated with the use of natural dyes in the dyeing of silk is the susceptibility of the dyed yarn to fading in light. While a number of approaches have been used to address this problem, the use of polydopamine (PDA), a known agent with photo‐protective properties, has not been assessed previously. In this study, silk was pretreated with nano‐particulate PDA formed in situ by oxidation of a dopamine solution, then dyed with lac dye or annatto dye as model natural dyes. Photofading rates were significantly reduced in the case of annatto‐dyed, PDA‐coated silk relative to uncoated silk, while wash fastness was unaffected and remained only moderately good. In contrast, no significant change was seen in photofading rates with treated or untreated lac‐dyed silk, and wash fastness was also unaffected. The PDA did not adversely affect resultant colour values if the concentration of the dopamine precursor was kept low. When this was done, acceptable colours were obtained in the dyed silk. Further investigation is warranted of PDA as a photofading protectant and mordant with other natural dyes on silk and other fibres.     

Topping of naturally dyed wool fabrics with different natural dye sources

Wool fabrics can be dyed with synthetic dyes and even with natural dyes. To present a different aspect to the coloration of wool, the current study was focused on a topping process (ie, the dyeing of wool that was already dyed) with different natural dye sources. For this purpose, the fabrics that were already dyed with a natural dye source were once again dyed with two different natural dyes. In bottom dyeing (bottoming), fabrics were dyed with hops (Humulus lupulus L.) in the presence of different mordanting agents. Then the dyed, washed and dried samples were once again dyed (topping) with two different natural dye sources. For topping, powdered madder and acorn were tested in direct dyeing of wool samples. Finally, the colour changes were analysed with the use of a spectrophotometer. The study demonstrates that such a process (ie, bottoming with hops in the presence of different mordanting agents and then topping with madder or acorn) can be a way of obtaining different shades and colours with sufficient/good fastness values by natural dyeing.     

Light fastness of naturally occurring anthraquinone dyes on nylon

Nylon fabric has been dyed with two purified components of Indian madder, purpurin (1,2,4-trihydroxyanthraquinone) and munjistin (1,3-dihydroxy-2-carboxyanthraquinone). The light and wash fastness of dyed and mordanted samples has been studied. Purpurin showed much better resistance to photofading than munjistin. It was found that the type of mordant and the method of mordanting significantly affected the rate and extent of photofading. The use of copper or ferrous sulphate gave high resistance to fading, whereas stannous chloride or alum did not. On the other hand, light fastness was improved when postmordanting was conducted with copper or ferrous iron, but pre-mordanting was superior in the case of stannous chloride or alum.     

Pretreatment of cotton fabrics with polyamino carboxylic acids for salt‐free dyeing of cotton with reactive dyes

In this study, polyamino carboxylic acids have been used to improve the dyeability of cotton in a salt‐free reactive dyeing process. These polyamino carboxylic acids were prepared by partial carboxylation of polyvinylamine. Cotton fabric was pretreated with polyamino carboxylic acids and dyed with reactive dyes. The colour strengths of the dyed fabrics were evaluated by measuring the K/S values. The fastness properties (washing, rubbing and light fastness) of the dyed cotton fabrics were also measured. The pretreatment of cotton with polyamino carboxylic acids creates positive charges on the fabric surface. In this way, salt‐free reactive dyeing of cotton or dyeing with only a small amount of electrolyte is possible.