Dyeing of natural fibres from perfluoro-polyether reverse micelles in supercritical carbon dioxide

The dyeing of natural fibres from a reverse-micellar system in supercritical carbon dioxide has been investigated using ammonium carboxylate perfluoropolyether as surfactant. Protein fibres such as silk and wool were satisfactorily dyed in deep shades with conventional acid dyes without special pretreatment. Exhaustion was excellent. It was however found that on these fibres the performance of acid dyes was strongly influenced by temperature and carbon dioxide density. Conventional reactive dyes in this system were adsorbed on cotton, even in the absence of dyeing auxiliaries, but the fixation of the dye was not satisfactory. Compared with supercritical dyeing methods reported previously, it was found in this study that the temperature and pressure required were significantly lower.     

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.     

Study of the dyeing properties of saffron and ultrafiltrated saffron powders,as colourants for natural and synthetic fibres

There is a noticeable growing interest in the use of natural dyes in contemporary textile dyeing, motivated by the requirements imposed, in favour of environmental prosperity. The use of natural dyes reduces significantly both the energy requirements and the environmental impact of the process. In the present work natural and synthetic fibres were dyed with the dyestuff isolated from Crocus sativus L., after aqueous extraction of the dried stigmas of the plant. Additionally, part of the powder was purified by using ultrafiltration technology. The saffron extract and the ultrafiltrated saffron retentate were used to dye cotton, wool, nylon and polyester, in various depths of shade and temperatures. Both saffron and ultrafiltrated saffron successfully dyed not only the natural substrates, but also the synthetic ones, while higher dyeing temperatures produced level dyeing with all substrates used. Ultrafiltrated saffron powder produced brighter and much stronger dyeing to the original saffron powder, due to the elimination of extraction by-products. Isothermal adsorptions for both colourants were performed on all substrates in order to investigate their adsorption mechanism. It was found that saffron and ultrafiltrated saffron follow a Freundlich-type adsorption isotherm on cotton, wool and nylon which is a typical mechanism for a planar-directed dye of big molecular weight. Nernst-type adsorption was found to occur on polyester which again is typical for the adsorption of disperse dyes on polyester. Thus, saffron can be claimed as a universal dye, able to successfully dye natural and synthetic substrates.     

Dyeing of cotton with the natural dye extracted from waste leaves of green tea (Camellia sinensis var. assamica)

Due to an increase in the production of green tea, the amount of leaf waste has increased enormously, causing serious environmental problems. With regard to environmental awareness, the possibility of reusing the waste leaves of green tea as a low‐cost and abundantly available source of natural dye for dyeing cotton fibres was investigated. Natural dye powder from the waste leaves of green tea (NDPT) was successfully applied to dye cotton fibres without mordant by batch experiments. NDPT was obtained as a dark brown powder with a yield of 2.7 ± 0.5% w/w from dried waste leaves of green tea. The optimal conditions for dyeing NDPT onto cotton fibres were: pH of dye solution, 3; material to liquor ratio, 100:1; dyeing time, 180 min; concentration of dye solution, 3.0 mg/ml; and dyeing temperature, 100 °C. The colour of cotton fibres dyed with NDPT was observed to be dark brown. The adsorption data of NDPT on cotton fibres was best fitted with a Langmuir adsorption isotherm model with a correlation coefficient (R²) of 0.997. It is clear that there is a strong possibility of reusing the waste leaves of green tea as a low‐cost and abundantly available source of natural dye for dyeing cotton fibres.     

Synthesis and Application of Some New Reactive Chlorohydrin Dyes

Azo and phthalocyanine dyes carrying the chlorohydrin group, as the precursor of the reactive epoxy group, were prepared using new catalyzed reactions. The reactive group is attached to the coupling component in some cases and to the diazonium component in other cases. A phthalocyanine dye carrying two reactive groups was also synthesized. The dyeing of cotton, wool and multifibre fabrics was studied, under different dyeing conditions. Various techniques of dyeing and printing were used. Exhaustion and padding methods were investigated for dyeing, and direct, reserve and discharge methods for printing. One–stage and two–stage procedures were employed for both printing and dyeing. It was found that the chlorohydrin reactive dyes prepared in the present work could be applied by nearly all known methods of dyeing and printing on cotton, wool, viscose rayon, nylon and acrylic fibres. The dyeings obtained had satisfactory fastness properties and showed fairly good dye fixation on the substrate.     

活性染料用于拉细羊毛染色的研究

研究了四类活性染料染拉细羊毛的工艺条件和十二个染色配方。与媒介染料相比，用活性染料对拉细羊毛染色可获得更好的效果。染料的溶解度、匀染性、上色率、固色率均好于媒介染料，颜色的批差小。研究结果表明：除煮呢沾色牢度外，染色羊毛的各项牢度均优于媒介染料。     

Dyeing natural fibres in supercritical carbon dioxide using a nonionic surfactant reverse micellar system

A reverse micellar system in supercritical carbon dioxide has been developed as a dyeing medium. Water-soluble dyes such as reactive dyes and acid dyes could be sufficiently solubilised in the interior of a specially constituted reverse micelle. Protein fabrics, silk and wool, were satisfactorily dyed even in deep shades with conventional acid dyes without any special pretreatment. Cotton cellulose fabric was also dyed with conventional reactive dyes when the electrostatic force of repulsion between dye and cotton was eliminated. Compared to previously proposed supercritical dyeing methods, dyeing of fabrics with this system could be performed at low temperatures and pressures in a short time.     

One‐bath union dyeing of a modified wool/acrylic blend with acid and reactive dyes

Pretreated wool/acrylic fibre was obtained by a facile amidoximation process. Fibre characterisation (nitrogen content, tensile strength, shrinkage, infrared spectra and X‐ray diffraction) proved the success of the pretreatment. Union dyeing of wool/acrylic fabrics with acid and reactive dyes, namely CI Acid Red 40, CI Acid Blue 25, CI Reactive Red 194 and CI Reactive Blue 25, was obtained using a one‐bath dyeing process. Different factors that may affect the dyeability of the blend fibre, such as dyebath pH, liquor ratio, temperature, time and dye concentration, were evaluated with respect to the dye exhaustion, fixation, colour strength, levelling and fastness properties. Excellent to good fastness was obtained for all samples, irrespective of the dye used. The result of the investigation offers a new viable method for union dyeing of wool/acrylic fibres in a one‐dyebath process.     

The role of natural dyes in the UV protection of fabrics made of vegetable fibres

The safest protection from ultraviolet (UV) radiation exposure is offered by textiles including various apparels, accessories such as hats and shade structures such as umbrellas. Their protectiveness depends on fabric composition, (natural, artificial or synthetic fibres), fabric construction (porosity, weight and thickness) and dyeing (natural or synthetic dyes, dye concentration, UV-absorbing properties, etc.). In this study the UV-protection properties were investigated on fabrics made of vegetable fibres (cotton, flax, hemp and ramie), with different construction parameters (drapery and apparel fabrics), dyed with some of the most common natural dyes. The effect of a tannins-based mordant (the galls of Quercus infectoria) on UV-protection capacity was also tested. UV radiation transmittance of fabrics was measured by two methods: one based on the utilisation of a spectrophotometer equipped with an integrating sphere (in vitro test), and the other based on outdoor measurements taken by a spectroradiometer. Transmittance measurements were used to calculate the Ultraviolet Protection Factor (UPF).Our results revealed that thick and dense (cover factor, CF > 94%) drapery fabrics made of vegetable fibres usually showed good UV-protection levels even if undyed. The use of the tannins-based mordant increased, even without dyeing, the UV-protection level up to the very good and/or excellent protection categories when fabric construction was suitable. Dyeing did not further increase the protection level.Lighter fabrics, usually used for apparel, even showed high UV-protection level after just dyeing, provided that CF was above 94%.Taking into account the high concentrations of dyes used in the present work and the utilisation of mordants containing tannins, slight differences in UV-protection capacity were detected among natural dyes tested and between the two different methods of transmittance measurement. However, UV-protection category defined from outdoor measurements was often higher than that calculated by the in vitro test, indicating an underestimation of the actual protection level of tested fabrics assessed by the latter.     

The role of natural dyes in the UV protection of fabrics made of vegetable fibres

The safest protection from ultraviolet (UV) radiation exposure is offered by textiles including various apparels, accessories such as hats and shade structures such as umbrellas. Their protectiveness depends on fabric composition, (natural, artificial or synthetic fibres), fabric construction (porosity, weight and thickness) and dyeing (natural or synthetic dyes, dye concentration, UV-absorbing properties, etc.). In this study the UV-protection properties were investigated on fabrics made of vegetable fibres (cotton, flax, hemp and ramie), with different construction parameters (drapery and apparel fabrics), dyed with some of the most common natural dyes. The effect of a tannins-based mordant (the galls of Quercus infectoria) on UV-protection capacity was also tested. UV radiation transmittance of fabrics was measured by two methods: one based on the utilisation of a spectrophotometer equipped with an integrating sphere (in vitro test), and the other based on outdoor measurements taken by a spectroradiometer. Transmittance measurements were used to calculate the Ultraviolet Protection Factor (UPF).Our results revealed that thick and dense (cover factor, CF > 94%) drapery fabrics made of vegetable fibres usually showed good UV-protection levels even if undyed. The use of the tannins-based mordant increased, even without dyeing, the UV-protection level up to the very good and/or excellent protection categories when fabric construction was suitable. Dyeing did not further increase the protection level.Lighter fabrics, usually used for apparel, even showed high UV-protection level after just dyeing, provided that CF was above 94%.Taking into account the high concentrations of dyes used in the present work and the utilisation of mordants containing tannins, slight differences in UV-protection capacity were detected among natural dyes tested and between the two different methods of transmittance measurement. However, UV-protection category defined from outdoor measurements was often higher than that calculated by the in vitro test, indicating an underestimation of the actual protection level of tested fabrics assessed by the latter.     

Color evaluation of wool fabric dyed with Rhizoma coptidis extract

Berberine is the only cationic colorant of natural plant dyes, which lies in the roots of Rhizoma coptidis and stems of phellodendron. In this study, wool fabric was dyed with the extracts of R. coptidis. Color evaluation was characterized with ΔE, L*, a*, b*, c*, H⁰, K/S. Effects of mordant, extraction concentration, pH value of dye bath, and treatment temperature on color values were studied. Results indicated that wool fabrics dyed with mordant, or at higher temperature, or in alkali solution possessed deeper shades and darker colors. And the wool fabric showed good antibacterial property after dyeing with R. coptidis extracts. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3376–3380, 2006     

Application of D‐optimal design in the analysis and modelling of dyeing of plasma‐treated wool with three natural dyes

Both the dyeing and finishing of textiles with natural compounds are gaining increasing attention because of various environmental and health problems associated with the use of synthetic reagents. In this study, wool fibres were dyed with three natural dyes, namely, Arnebia euchroma, cotton pods and harmal seeds. Alum was used as the mordant, and samples were mordanted by the premordanting method. Oxygen plasma was employed for the surface modification of wool. Plasma treatment time, alum concentration, dyebath temperature and pH were selected as the process variables, and their effects on the K/S of the dyed samples were analysed using D‐optimal design. The surface topography, morphology and chemistry of the wool fibres after plasma treatment were studied by atomic force microscopy (AFM), scanning electron microscopy (SEM) and Fourier Transform–infrared spectroscopy (FTIR), respectively. FTIR confirmed the creation of new oxygen‐containing groups on the surface of wool fibres after plasma treatment. SEM and AFM images confirmed the surface etching and increase in the roughness of plasma‐treated fibres. Increasing the dyebath pH and temperature increased the K/S of the dyed samples. Increasing the amount of alum mordant increased the K/S of samples dyed with cotton pods but decreased the K/S of samples dyed with A. euchroma and harmal seeds. Increasing the plasma treatment time improved the K/S of samples dyed with A. euchroma and cotton pods but had no significant effect on the K/S of samples dyed with harmal seeds.     

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.     

Mechanical Properties and Stability to Light Exposure for Dyed Egyptian Cotton Fabrics with Natural and Synthetic Dyes

Synthetic dyes are more available than natural dyes were in the past, because of lower prices and wider ranges of bright shades with considerably improved color fastness properties. In current years, concern for the environment has created an increasing demand for natural dyes, which are friendlier to the environment than are synthetic dyes. The aim of this work is to study the effect of dyeing cotton fabrics with both a natural dye (henna) and a synthetic dye (Remazol blue) on some mechanical properties and those of stability to light exposure. The undyed and dyed cotton fabrics were tested for their mechanical behaviors expressed as tenacity (N), elongation %, and work-breaking (N · m). They were also tested for shrinkage and crease recovery angle. The stability to light before and after 100 h exposure was examined by investigating the microstructure [using x-ray diffraction (XRD)] and macrostructure [using a scanning electron microscope (SEM)] and the reflection spectra. The results proved that the cotton samples dyed with Henna dye have higher mechanical properties than those dyed with “Remazol” reactive dye. Moreover, the light fading behaviors of both synthetic and natural dyes were studied in terms of the reflection spectra (400–800 nm), microstructure, and macrostructure of the sample's fibers.     

Extraction of polyphenolic substances from bark as natural colorants for wool dyeing

In Europe, considerable amounts of bark are available from wood‐processing industries such as forestry and timber production. Polyphenolic components can be collected by hot water extraction. The extracted compounds can then be applied as colorants in textile dyeing operations. In this study, a comparative assessment of four different tree species with regard to their colouristic potential for wool dyeing was performed. Aqueous extracts from alder, ash tree, spruce and oak bark were prepared and analysed for their total phenolic content and ultraviolet (UV) absorption at 360–370 nm. The extracts were used for meta‐mordant dyeing by adding iron sulphate mordant (FeSO₄ × 7H₂O). For comparison, iron salt‐based dye lakes were prepared and used in dyeing experiments. For each tree species, a specific correlation between the total phenolic content of the dyebath and the colour depth in terms of K/S and CIELab coordinates was observed, both for the aqueous extracts and the dye lakes. Based on this relationship, standardisation and quality control of raw materials and dye lakes can be installed as important stages in the industrialisation of natural colorants from bark. The preparation of concentrated dye lakes permits formation of a concentrated colorant as dye product, which then can be standardised and delivered to textile dyehouses, similar to synthetic dyes. The preparation of dye lakes offers a relevant route towards achieving the commercialisation of bark extracts as natural colorants.     

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.     

槐米染色棉织物工艺及其抗紫外性能研究

为实现槐米染料的工业化应用及提高棉织物的功能性,分析了使用壳聚糖、Al3+、Fe2+媒染剂预媒染色法对棉织物染色效果的影响,重点研究了铝预媒染方法染色温度、染色时间、pH值等工艺参数对染色棉织物K/S值的影响,并测试了槐米染色棉织物的抗紫外性能。结果表明:直接使用槐米染色的效果较差;壳聚糖媒染对上染效果影响不大,使用铝、铁媒染剂,可得到不同颜色的棉织物;铝媒染剂染色棉织物为鲜艳的黄色,为较好的媒染方法;铝预媒染染色方法染色优化条件为:温度为80℃,染色时间120分钟,染浴pH值为6.8;铝预媒染染色棉织物具有较好的抗紫外性能。     

Influence of liquor ratio and amount of dyestuff in producing ultradeep black dyeing using mercerised and cationised cotton

Cationised cotton allows the dyeing of cotton fabrics without salt and up to 100% anionic dye utilisation. The employment of cationised cotton in the dyeing of high depths of shades with reactive dyes holds marked potential for sustainable improvements through less dye consumption, decreased water usage, and zero salt utilisation, all while obtaining shade depths darker than possible with conventional reactive dyeings. This work builds upon previous work in obtaining ultradeep dyeings of cotton utilising cationised and mercerised cotton by investigating the effects of liquor ratio in dyeing and amount of dye applied. Surprisingly, for mercerised only cotton fabric, it was found that nearly equivalent depths of shade, as indicated by L*, were obtained, irrespective of the liquor ratio and the amount of CI Reactive Black 5 applied from 7% to 10% owf. However, the strengths of the dyeings, indicated by the K/S sum, show slight increases with increasing amounts of dye, but not when the liquor ratio is lowered. Similarly, for mercerised‐cationised cotton, the liquor ratio had a negligible effect on the depth of shade obtained, but increasing the amount of CI Reactive Black 5 resulted in an increase in shade depth and colour strength. Very deep shades with high colour strength were obtained with mercerised‐cationised cotton that were not obtainable with uncationised cotton, even at a very low liquor ratio and with a drastic increase in the amount of CI Reactive Black 5.     

牡丹花天然植物染料对羊毛织物染色性能的研究

将黄色牡丹花天然植物染料用于羊毛织物的染色,探讨了媒染剂和染色方法对羊毛织物染色效果的影响,通过单因素试验和正交试验筛选出以明矾为媒染剂时牡丹花黄色染料对羊毛织物的最佳染色工艺条件,得到了色泽鲜艳的黄色羊毛织物.     

Synthesis and application of a novel,triphendioxazine‐based,phosphorus‐containing acid dye for wool

A novel phosphorus‐containing acid dye based on triphendioxazine was designed and synthesised from diphenylamine through a series of reactions. The dye has a navy‐blue colour, high molar extinction coefficient of 5.32 × 10⁴ l/mol·cm, and high substantivity for dyeing wool in a salt‐free, aqueous dyebath. A high exhaustion value of 98.2% on wool fabrics was recorded at 3% omf and a liquor ratio of 1:20. The wash fastness values of the acid dye, including colour change and staining on cotton and wool, were grades 5, 4 and 4–5, respectively. The dry and wet fastness are grades 4–5 and 4, respectively. In addition, light fastness reaches grades 6–7 at 3% omf dye concentration. These dye properties are better than those of commercial triphendioxazine dyes, for example, CI Direct Blue 106 and CI Reactive Blue 198, under analogous dyeing conditions.