China
Africa
Explore chapters and articles related to this topic
Dyes and their application
Published in Michael Hann, Textile Design, 2020
There are numerous synthetic dyes. Probably the most important are acid dyes; azoic dyes; basic dyes; chrome or mordant dyes; direct dyes; disperse dyes; reactive dyes; sulphur dyes; vat dyes; pigments. The suitability of each to particular fibre types is identified below. Acid dyes can be used in the dyeing of wool, specialty hair fibres, silk and polyamide fibres. Azoic dyes are used mainly for cellulosic fibres. Basic dyes, first developed during the nineteenth century, have particularly pure and brilliant colours on fibres such as silk (and other animal fibres) but have very poor all-round fastness (Storey, 1978: 75) and, by the late-twentieth century, were only used to a limited extent in textile dyeing, especially of acrylics. Chrome dyes are used widely in wool dyeing. They are simple in application and retain good light and wet fastness. Direct dyes are regarded as the simplest class of dyes. They are readily soluble in water and are used mainly to dye natural cellulosic fibres as well as viscose. Fibrous material is simply placed in a weak solution and heated. Exhaustion of the direct dye improves with the presence of common salt, and an increase in temperature can increase the rate of dye uptake. Giles described various after-treatments which would help to improve the wet fastness of direct dyes (Giles, 1971: 61). Disperse dyes are suited to secondary acetate, triacetate and polyamide fibres, as well as acrylic and polyester fibres. Disperse dyes are regarded as the main dye class for synthetic fibres. Reactive dyes are used mainly for cellulosic and wool fibres but have been used with some success in the dyeing of silk also. Further details were provided by Giles (1971: 73). Sulphur dyes are used widely in a soluble form on cottons and provide fast colours. Vat dyes are used mainly for cellulosic fibres and have excellent all-round fastness. Pigments are suited to all fibres and their combinations. A summary of the main dye types and their properties was given in tabular form by Wynne (1997: 259).
Dyes
Published in Pankaj Chowdhary, Abhay Raj, Contaminants and Clean Technologies, 2020
Disperse dyes are nonionic, water-insoluble dyes and are used for applying on hydrophobic fibers from an aqueous dispersion. These dyes are mainly used in coloring polyester and minimally used in coloring nylon, cellulose, cellulose acetate, and acrylic fibers.
Dyes and Auxiliaries for Textile Printing
Published in Asim Kumar Roy Choudhury, Principles of Textile Printing, 2023
The Society of Dyers and Colourists (UK) defines disperse dye as a substantially water-insoluble dye having substantivity for one or more hydrophobic fibers such as cellulose acetate or polyester, and usually applied from fine aqueous dispersion.
Recent advance in enhanced adsorption of ionic dyes from aqueous solution: A review
Published in Critical Reviews in Environmental Science and Technology, 2023
Hydrophobic interaction is rare in dye adsorption. Most dyes have strong hydrophilicity for easy coloring. Disperse dyes are a kind of dyes without water-soluble groups. As shown in Figure 2b, there are few studies related to the adsorption of dispersed dyes. For example, the region of the benzene ring and ester group (–COOCH3) in the cationic dye Rh 6 G is hydrophobic. Zha et al. prepared hydrophobic UiO-66-NHCOR via iso stearin chloride functionalization. The contact angle of the hydrophobically modified Uio-66 increased from 32° to 158°. The adsorption capacity of the hydrophilic Uio-66 for Rh 6 G was only 243 mg/g, while the hydrophobic UiO-66-NHCOR increased its adsorption capacity to 478 mg/g. FTIR showed that in addition to electrostatic forces, the hydrophobic groups of Rh 6 G had a strong tendency to aggregate with the hydrophobic domains of UiO-66-NHCOR (Zha et al., 2019).
Tuning the aqueous solubility, chemical reactivity and absorption wavelength of azo dye through systematic adjustment of molecular charge density: a DFT study
Published in Molecular Physics, 2020
Olaide O. Wahab, Lukman O. Olasunkanmi, Krishna K. Govender, Penny P. Govender
Disperse dyes are sparingly soluble nonionic dyes that are mainly used for colouring hydrophobic materials such as polyesters, nylons, acrylics and cellulose acetates. Due to their low aqueous solubility, they do not form a homogenous dye solution with ordinary water. Therefore, when dyeing is performed in water at moderate temperatures, dispersing/solubilising and carrier agents are usually added to obtain a finely and evenly dispersed homogenous medium for easier penetration of dye molecules into the substrates [1–5]. Unfortunately, addition of dispersing/solubilising agents does not only increase production costs, but can also interfere with safety [1,3–5] because, most of the carrier agents contain toxic substances such as o-phenylphenol, phthalates, biphenyls and chlorinated aromatic compounds [2,6]. In addition, most carriers are non-biodegradable, and are also capable of plasticising fibres, which consequently lowers the glass transition temperature (Tg) of the fibres [5,6].
Application of polyamidoamine dendrimer in reactive dyeing of cotton
Published in The Journal of The Textile Institute, 2018
Saptarshi Maiti, Geetal Mahajan, Shyam Phadke, Ravindra V. Adivarekar
In textile dyeing processes there are different type of dyestuffs generally selected for particular classes of fibres. For example disperse dyes are usually used for dyeing of polyester and polyamide fibres like nylon (Esfandiari & Hajilari, 2006). Similarly reactive dyes are mostly used for dyeing of cellulosic fibres like cotton. Now, in case of reactive dyes, the dyes react with hydroxyl group of the fibre by either substitution or addition reaction based on the reactive group in the dye (Chattopadhyay, Pan, & Day, 2006). In order to react with cellulosic fibres like cotton, reactive dyes profusely depend upon large amounts of electrolyte (NaCl or Na2SO4) for exhaustion and elevated pH (commonly over 10.5) for fixation to achieve satisfactory results. Electrolyte is essential to overcome the static repulsion between cotton fibres and reactive dyes in order to enhance dyeability. While dyeing, apart from dye absorption, dye hydrolysis also takes place. The major problem is dye hydrolysis i.e. the reaction of dyes with water since it blocks the reactive sites of dye that prevent reactive dye to form covalent bond with fibres. Moreover, the hydrolysed dye is retained on the fabric that is removed by severe washing and results in wastage of dye. The hydrolysis of dye with water greatly takes place at higher pH values. Thus considering large usage of electrolyte, and alkali and subsequent hydrolysis leading to wastage of dye, the application of reactive dyes on cellulosic fibres can be considered costly for the dye house. In addition, there is also a problem of large pollution load for the environment.