A dye is a coloured substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they colour. The dye is generally applied in an aqueous solution , and may require a mordant to improve the fastness of the dye on the fiber. Both dyes and pigments are colored, because they absorb only some wavelengths of visible light. Dyes are usually soluble in water whereas pigments are insoluble.
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- The Birth of (Synthetic) Dyeing
- Textile Dyes: Dyeing Process and Environmental Impact
- Textile Engineering & Fashion Technology
- Natural dyes v synthetic: which is more sustainable?
- Chemical and Synthetic Dyes
- Natural vs. Synthetic Dyes: Which is Better?
- Natural dye
- Synthetic Pigments
- Project Report on Technology Of Synthetic Dyes, Pigments & Intermediates (hand Book)
The Birth of (Synthetic) Dyeing
A dye is a coloured substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they colour. The dye is generally applied in an aqueous solution , and may require a mordant to improve the fastness of the dye on the fiber. Both dyes and pigments are colored, because they absorb only some wavelengths of visible light.
Dyes are usually soluble in water whereas pigments are insoluble. Some dyes can be rendered insoluble with the addition of salt to produce a lake pigment.
The majority of natural dyes are derived from plant sources: roots , berries , bark , leaves , wood , fungi and lichens. Other than pigmentation, they have a range of applications including organic dye lasers ,  optical media CD-R and caera sensors color filter array. Textile dyeing dates back to the Neolithic period. Throughout history, people have dyed their textiles using common, locally available materials. Scarce dyestuffs that produced brilliant and permanent colors such as the natural invertebrate dyes Tyrian purple and crimson kermes were highly prized luxury items in the ancient and medieval world.
Plant-based dyes such as woad , indigo , saffron , and madder were important trade goods in the economies of Asia and Europe. Across Asia and Africa, patterned fabrics were produced using resist dyeing techniques to control the absorption of color in piece-dyed cloth. Dyes from the New World such as cochineal and logwood were brought to Europe by the Spanish treasure fleets,  and the dyestuffs of Europe were carried by colonists to America.
Dyed flax fibers have been found in the Republic of Georgia in a prehistoric cave dated to 36, BP. Early dyes were obtained from animal , vegetable or mineral sources, with no to very little processing.
By far the greatest source of dyes has been from the plant kingdom , notably roots, berries, bark, leaves and wood, only few of which are used on a commercial scale. The first synthetic dye, mauve , was discovered serendipitously by William Henry Perkin in Other aniline dyes followed, such as fuchsine , safranine , and induline.
Many thousands of synthetic dyes have since been prepared. In Paul Ehrlich discovered that certain cells or organisms took up certain dyes selectively. He then reasoned that a sufficiently large dose could be injected to kill pathogenic microorganisms, if the dye did not affect other cells. Erlich went on to use a compound to target syphillis, the first time a chemical was used in order to selectively kill bacteria in the body, he also used methylene blue to target the plasmodium responsible for malaria.
An earlier theory known as Witt theory stated that a coloured dye had two components, a chromophore which imparts colour by absorbing light in the visible region some examples are nitro , azo , quinoid groups and an auxochrome which serves to deepen the colour. Dyes are classified according to their solubility and chemical properties.
Acid dyes are water - soluble anionic dyes that are applied to fibers such as silk , wool , nylon and modified acrylic fibers using neutral to acid dye baths. Attachment to the fiber is attributed, at least partly, to salt formation between anionic groups in the dyes and cationic groups in the fiber. Acid dyes are not substantive to cellulosic fibers. Most synthetic food colors fall in this category. Basic dyes are water-soluble cationic dyes that are mainly applied to acrylic fibers , but find some use for wool and silk.
Usually acetic acid is added to the dye bath to help the uptake of the dye onto the fiber. Basic dyes are also used in the coloration of paper. Direct or substantive dyeing is normally carried out in a neutral or slightly alkaline dye bath, at or near boiling point , with the addition of either sodium chloride NaCl or sodium sulfate Na 2 SO 4 or sodium carbonate Na 2 CO 3.
Direct dyes are used on cotton , paper, leather , wool, silk and nylon. They are also used as pH indicators and as biological stains. Mordant dyes require a mordant , which improves the fastness of the dye against water, light and perspiration. The choice of mordant is very important as different mordants can change the final color significantly. Most natural dyes are mordant dyes and there is therefore a large literature base describing dyeing techniques. The mordant potassium dichromate is applied as an after-treatment.
It is important to note that many mordants, particularly those in the heavy metal category, can be hazardous to health and extreme care must be taken in using them. Vat dyes are essentially insoluble in water and incapable of dyeing fibres directly.
However, reduction in alkaline liquor produces the water-soluble alkali metal salt of the dye. This form is often colorless, in which case it is referred to as a Leuco dye , and has an affinity for the textile fibre.
Subsequent oxidation reforms the original insoluble dye. The color of denim is due to indigo , the original vat dye. Reactive dyes utilize a chromophore attached to a substituent that is capable of directly reacting with the fiber substrate. The covalent bonds that attach reactive dye to natural fibers make them among the most permanent of dyes. Reactive dyes are by far the best choice for dyeing cotton and other cellulose fibers at home or in the art studio.
Disperse dyes were originally developed for the dyeing of cellulose acetate , and are water-insoluble. The dyes are finely ground in the presence of a dispersing agent and sold as a paste, or spray-dried and sold as a powder.
Their main use is to dye polyester , but they can also be used to dye nylon, cellulose triacetate , and acrylic fibers. The very fine particle size gives a large surface area that aids dissolution to allow uptake by the fiber. The dyeing rate can be significantly influenced by the choice of dispersing agent used during the grinding.
Azoic dyeing is a technique in which an insoluble Azo dye is produced directly onto or within the fiber. This is achieved by treating a fiber with both diazoic and coupling components. With suitable adjustment of dyebath conditions the two components react to produce the required insoluble azo dye. This technique of dyeing is unique, in that the final color is controlled by the choice of the diazoic and coupling components.
This method of dyeing cotton is declining in importance due to the toxic nature of the chemicals used. Sulfur dyes are inexpensive dyes used to dye cotton with dark colors. Dyeing is effected by heating the fabric in a solution of an organic compound, typically a nitrophenol derivative, and sulfide or polysulfide. The organic compound reacts with the sulfide source to form dark colors that adhere to the fabric. Sulfur Black 1, the largest selling dye by volume, does not have a well defined chemical structure.
One other class that describes the role of dyes, rather than their mode of use, is the food dye. Because food dyes are classed as food additives , they are manufactured to a higher standard than some industrial dyes. Food dyes can be direct, mordant and vat dyes, and their use is strictly controlled by legislation. Many are azo dyes, although anthraquinone and triphenylmethane compounds are used for colors such as green and blue.
Some naturally occurring dyes are also used. By the nature of their chromophore , dyes are divided into: . Dyes produced by the textile, printing and paper industries can end up in waste waters and are therefore a potential source of pollution of rivers and waterways.
Various porous materials, often used to adsorb harmful chemicals in general, have been specifically tested to remove dyes from aqueous environments, especially those who could combine wide availability, fast kinetics and strong adsorption capacities.
Possible examples include nickel oxide nanoplates,  clays,  activated carbons,  composites of hydroxyapatite with organic substrates,   graphene oxides. From Wikipedia, the free encyclopedia. For other uses, see Dye disambiguation. Main article: Natural dye. Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. Artisan Books.
Retrieved 8 November — via Google Books. Laser Fundamentals. Cambridge University Press. CRC Press. Courier Corporation. Bibcode : Sci Chemie in Unserer Zeit. Travis Technology and Culture. Industrial Dyes. Chemistry, Properties, Applications. Color Chemistry. Environmental Reviews. Dye Laser Principles.
New York. Archived from the original on 12 June Retrieved 8 November Archived from the original on 16 April Chemistry World. Retrieved June Journal of Environmental Management.
That brilliant, fire-engine red colour of your favourite dress, the royal purple of your favourite shirt and even the earthy brown of your fluffy bath towel has been achieved in one of two ways; the use of natural dyes or the use of synthetic dyes. By definition; natural dyes refer to pigments that exist organically and are produced from plants, animals or naturally-occurring minerals without the involvement of any chemicals in the process. For example,. Typically, natural dyes are preferred when producing textiles because they occur naturally in nature, have a pleasant natural smell and a rich appearance. To achieve consistency, the plants need to be grown in a controlled environment. This approach is impractical, given the high amount of dye required for mass production of textile.
Textile Dyes: Dyeing Process and Environmental Impact
Regret for the inconvenience: we are taking measures to prevent fraudulent form submissions by extractors and page crawlers. Received: August 18, Published: July 14, Citation: Choudhury AKR. Green chemistry and textile industry. J Textile Eng Fashion Technol. DOI: Download PDF.
Textile Engineering & Fashion Technology
Synthetic dyes are manufactured from organic molecules. Before synthetic dyes were discovered in , dyestuffs were manufactured from natural products such as flowers, roots, vegetables, insects, minerals, wood, and mollusks. Batches of natural dye were never exactly alike in hue and intensity, whereas synthetic dyestuffs can be manufactured consistently. The use of computers and computer color matching CCM produces color that is identical from batch to batch. William Henry Perkin, an eighteen-year-old English chemist, was searching for a cure for malaria, a synthetic quinine, and accidentally discovered the first synthetic dye. He found that the oxidation of aniline could color silk. From a coal tar derivative he made a reddish purple dye.
Natural Science Vol. Color is the main attraction of any fabric. No matter how excellent its constitution, if unsuitably colored it is bound to be a failure as a commercial fabric. Manufacture and use of synthetic dyes for fabric dyeing has therefore become a massive industry today. In fact the art of applying color to fabric has been known to mankind since BC. WH Perkins in discovered the use of synthetic dyes. Synthetic dyes have provided a wide range of colorfast, bright hues. However their toxic nature has become a cause of grave concern to environmentalists. Use of synthetic dyes has an adverse effect on all forms of life. Presence of sulphur, naphthol, vat dyes, nitrates, acetic acid, soaps, enzymes chromium compounds and heavy metals like copper, arsenic, lead, cadmium, mercury, nickel, and cobalt and certain auxiliary chemicals all collectively make the textile effluent highly toxic.
Natural dyes v synthetic: which is more sustainable?
We are committed to help to move forward to a sustainable and just society of well-being, contributing to an accelerated transition to sustainable lifestyles. The Greendyes process is the result of the search for excellence in terms of efficiency. Share this: Twitter Facebook Panel 3. We only accept new raw materials if: 1 Provides the maximum colorfastness.
Even benign chemicals like potato starch will kill fish and other aquatic life because they encourage the growth of algae which depletes all available oxygen, among other issues known as BOD or Biological Oxygen Demand. So be sure to buy fabric from a supplier who has water treatment in place. The other part of the equation is how the dye is formulated, because if toxic chemicals are used in the formulation then most of these chemicals remain in the fabric. If synthetic chemical dyestuffs contain chemicals which can poison us, then the use of natural dyes seems to many people to be a safer alternative. So what are natural dyes? Natural dyes are dyes derived from animal or plant material without any synthetic chemical treatment. They are obtained from sources like flowers, leaves, insects, bark roots and even minerals. The most common natural dyes all from plants except cochineal, from an insect are:. Mushrooms can be poisonous.
Chemical and Synthetic Dyes
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Natural vs. Synthetic Dyes: Which is Better?
Synthetic Pigments Known as imperial purple, only those of a high status were allowed to wear it. The table below lists various fibers along with brief descriptions of each. With so many diverse synthetic fabric iterations on the market, we thought it was high time to offer a dye capable of taking those very fabrics to the next level. A wide variety of synthetic pigment options are available to you, such as ceramic pigments, coating pigment, and ink pigments. Most pigment ink printers may use up to eight different ink colors: cyan, light cyan, magenta, light magenta, yellow, light gray, medium gray and black. In addition to high quality dyes, Chromatech has laboratories across the globe that can help our customers by testing colorants, dyes, pigments, and pigment dispersions in customer applications and conditions. Small amounts of carbon black are added to obtain tinting colors not obtainable when synthetic brown iron oxide or carbon black are used singly. Synthetic iron oxides are the result of chemical processes and being human-made, they offer many color options.
Eco-Friendly Textile Dyeing and Finishing. Dyes may be defined as substances that, when applied to a substrate provide color by a process that alters, at least temporarily, any crystal structure of the colored substances [ 1 , 2 ]. Such substances with considerable coloring capacity are widely employed in the textile, pharmaceutical, food, cosmetics, plastics, photographic and paper industries [ 3 , 4 ]. The dyes can adhere to compatible surfaces by solution, by forming covalent bond or complexes with salts or metals, by physical adsorption or by mechanical retention [ 1 , 2 ].
Project Report on Technology Of Synthetic Dyes, Pigments & Intermediates (hand Book)
It was the first of the triphenylmethane dyes and triggered the second phase of the synthetic dye industry. Other reagents were found to give better yields, leading to vigorous patent activity and several legal disputes. Inadvertent addition of excess aniline in a fuchsine preparation resulted in the discovery of aniline blue, a promising new dye, although it had poor water solubility.
Baid and her husband, Arun, have figured out how to use natural dyes at scale at their factory in Ahmedabad, India. Discovered in the midth century by English chemist William Henry Perkin , mauveine, the first man-made colour, transformed textile manufacturing. These synthetic colours allowed manufacturers and dye houses to operate in large quantities, and offer vivid, rich colours.