Sulphur dyes are one of the most used dyes for producing bright black and brown shade on cellulosic fiber products. The chemistry of sulphur dyes dyeing is near similar to vat dyes dyeing. In both case final color is developed by the oxidation process. Although, reactive dyes, azoic color is available but sulphur dyes is preferable for black shade production.
Sulphur dyes are so called because sulphur dyes contain di-sulphide (S-S) linkage in their chemical structure. Sulphur dyes dyeing process is carried out in alkaline condition. Sulphur dyes are used for both dyeing and printing.
Properties of sulphur dyes:
- Sulphur dye is water insoluble dye.
- It needs solubilization for application (with reducing agent).
- Oxidation is needed for final color development.
- Sulphur dye is applied in alkaline condition.
- Electrolyte can be added in the dye to enhance exhaustion of dyes.
- Fastness properties are average.
- Best suitable for producing black and brown shade on the textile materials.
- It is mainly applied on cotton, viscose and staple fiber.
- Its exhaustion properties are good.
- Most of the times dyeing is carried out in 80-95 degree Celsius.
- Sulphur dye is comparatively cheap in price.
Although sulphur dyes have a lots of advantage but it has some disadvantage like-
- Bronziness of shade: For this defect some white spot can be appear in the fabric.
- Sulphur black tendency: This have sulphur black tendency.
So, when you will choose your dyes; check out the properties which should have dyes.