A dye is a coloring material that is used for imparting color to different substances or altering the color of something. Dyes have chromophores and auxochromes which are responsible for their color and substantivity
- Basic/Reactive dyes:
Reactive dyes have a halogen-containing reactive group present in their structure and become an integral part of the fiber structure by creating a covalent bond. This is the type that is mostly used for dyeing cotton fabrics.
- Disperse Dyes:
Disperse dyes are sparingly water-soluble dyes used for dyeing hydrophobic thermoplastic fibers. These dyes are mainly substituted azo, anthraquinone, or diphenylamine compounds.
- Direct dyes:
We can apply these dyes directly on the fiber as they have a strong affinity and so they are called direct dyes. Mainly these dyes are sodium salts of sulphonic acid or carboxylic acid, and their leading chromophoric group is azo. They are also known as substantive dyes
- Acid Dyes:
The application of acid dyes requires an acidic bath. They are mainly carboxylic or sulphuric acid salts. These are the types that are mainly used for dyeing protein fibers.
- Vat Dyes:
These dyes generally consist of a keto group in their structure and are made water-soluble by vatting. Their application process of vat dyes is quite similar to sulfur dyes. They are mainly used for dyeing denim or jeans.
- Sulphur dyes:
Sulfur dyes are quite similar to vat dyes. They are hugely used for producing black and brown shades in cotton. They have a disulfide linkage in their structure.
Scouring –
Scouring is a process of removing impurities such as oil, wax, fats, dust and dirt from textile material to make it hydrophilic
Bleaching
Bleaching is the destruction of natural coloring(Gray) matters to produce a white material.
Mercerising:
Mercerization is a process in which textiles (typically cotton) are treated with a caustic (NaOH) solution to improve properties such as fiber strength, shrinkage resistance, luster, and dye affinity. The caustic actually rearranges the cellulose molecules in the fiber to produce these changes.
Sanforising:
Sanforization is a process of pre-shrinking fabric before it is made into a garment. When a fabric has been treated with the sanforization process, it’s referred to as ‘sanforized’ or ‘pre-shrunk
Heat setting stretch fibres:
Heat-setting is a common way of reducing or eliminating dimensional instability. The heat-setting process typically involves passing the fabric through a heating zone for a time and at a temperature that resets the synthetic fiber’s morphology memory to the dimensions of the fabric at the time when the heat-setting process was applied. The time and temperature needed for the heat treatment depend on factors such as the fabric construction, the weight of the fabric, the type of synthetic fiber, other fibers present in the fabric, and the previous heat history of the synthetic fiber. The issue of dimensional instability is especially pronounced for stretch fabrics, particularly knitted stretch fabrics.