Direct dyes are sodium salt of sulphonic acid and most of them contain an azo group as the main chromophore. Additionally, direct dye dyeing is carried out in alkaline conditions. This dyeing process is done comparatively at low temperatures. After absorbing dyes it tends to bleed of dyes which produce unevenness of shade, to resist these different types of after treatment is done.
Uses of Direct Dyes
Direct dyes are anionic dyes substantive to cellulosic fibers when applied from an aqueous bath containing electrolytes. 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. The following are the main properties of direct dyes. They are-
- Firstly, direct dyes are water soluble dyes.
- Secondly, it is anionic in nature.
- Thirdly, it needs electrolyte for exhaustion.
- Dyeing process is carried out simultaneously in alkaline condition.
- Generally applied for cellulosic as well as protein fibers.
- Therefore, fastness properties are average specially wet fastness.
- Fastness properties are also improved by after treatment.
- In fact, it is not widely used as compared with reactive dyes.
- Comparatively cheap in price.
- Lastly, direct dyes are used for cheap goods for local market.
So, choose your direct dyes according to your requirements.