Direct dyes are sodium salt of sulphonic acid and most of them contain an azo group as the main chromophore. Direct dye dyeing is carried out in alkaline condition. This dyeing process is done comparatively in low temperature. After absorbing dyes it tends to bleeding of dyes which produce unevenness of shade, to resist these different types of after treatment is done.
Direct dyes are anionic dyes substantive to cellulosic fibers when applied from an aqueous bath containing electrolyte. Many of them also dye protein fibers. Direct dyes are very easy to apply and available in the market.
Properties of direct dyes: Direct dyes have some characteristics. Followings are the main properties of direct dyes.
- Direct dyes are water soluble dyes.
- It is anionic in nature.
- It needs electrolyte for exhaustion.
- Dyeing process is carried out in alkaline condition.
- Generally applied for cellulosic as well as protein fibers.
- Fastness properties are average specially wet fastness.
- Fastness properties are improved by after treatment.
- It is not widely used as compared with reactive dyes.
- Comparatively cheap in price.
- Direct dyes are used for cheap goods for local market.
So, choose your direct dyes according to your requirements.