Dyeing and dyes; this two word is related with one another. Without dyes it’s not possible to dye materials. So dye is the main thinking of dyeing. But most of time we do something wrong for what we face a lots of problem during dyeing. For this reason we should know about dyes, which we use in our dyeing process.
Dyes are coloring materials used in dyeing textiles. Other hand it can be defined as a substance which may be natural or synthetic use to change or add color to the textile materials. Applying of dyes on materials depends on the type of materials. Different materials have different chemical structure and different dyes had different chemical structure, so we have to know which dye is suitable for which materials.
Depending on dyes chemical structures, it is classified as bellow:
- Water soluble dyes:
- Direct dyes
- Acid dyes
- Basic dyes
- Reactive dyes
- Optical whiteners
- Water insoluble dyes:
- Vat dyes
- Sulphur dyes
- Disperse dyes
- Azoic colors
- Oxidation colors
- Mineral colors
Natural dyes are the dyes which are produced naturally from different plant source like roots, leaves, bark, berries and fungi, wood, lichens etc. Very beginning of the dyeing history man started dyeing their materials by natural dyes. Indigo, woad, saffron and madder are the plant based dyes which is much popular in Asia.
Synthetic dyes occupied the marked of dyes. Now a day most of the dyeing operation is done by synthetic dyes. Different factor is responsible for it. Synthetic dye is made from the reaction of two or more chemicals.
Another dye is food dye, which is not as an industrial dye. A higher standard is maintained during processing. It generally used as a food additives. Generally direct dyes, vat dyes and mordant dyes are used. Food dyes standard also controlled hardly by legislature.
Dyes can be water soluble or water insoluble. Some dyes are anionic, some are cationic or some has both anionic and cationic properties. Some dyes need low temperature and pressure for make a solution, some needs high temperature and pressure for make a solution. All of the properties of dyes depend on the molecular structure of dyes.
Now, dye molecule bears some group which is responsible for producing a color. Chromophore group is responsible for color production. The color bearing unsaturated group of a dye molecule is called Chromophore group. Some chromophore groups name is given bellow:
We know about Chromogen. The compounds containing a chromophore are called Chromogen. We know that the leaves of plant are green because it contains chromogen. Also Auxochrome is color helping group, it does not produce color itself but depends on the color of chromogen. Auxochrome may be acidic either basic like OH or NH2, COOH, NR2 etc.
Dyes are very sensitive to atmospheric condition. So it needs to keep in a standard atmospheric condition. Different world famous companies are trying to improve the properties of dyes. So by the research we can get more efficient dyes for the next day.