Direct Dyes — Overview & Major Types
The direct dyes are popular for their simple production method, complete chromatography, low cost, and easy application.
However, their soaping fastness and light fastness are relatively poor.
Direct dyes have been widely used for the dyeing of cellulose fibers, protein fibers, synthetic fibers, and their blended fabrics.
Major Types of Direct Dyes
Anionic Direct Dyes
• Used for coloring papers, controlling tint and shade, and correction of two-sided paper color.
• The main structural features of Anionic Direct Dyes are:
– The molecular structure is planar but varies among dyes.
– The single and double bonds are highly extended.
– Contains one or more sulfonate groups that make them soluble in water.
Cationic Direct Dyes
• The main structural features of Cationic Direct Dyes are:
– The structural single and double bonds are extended.
– The molecular structure is planar.
– Positive charges are greater than negative charges.
