Question

Ionic dyes used in printing is not suitable for

• A. wool
• B. silk
• C. casein
• D. polypropylene

Hint:

Ionic dyes (acid, basic, direct) require fibers with ionic or polar groups to bond. Polypropylene is a non-polar, hydrocarbon fiber and cannot be dyed with ionic dyes.

Answer 1

The Correct Option is D

Step 1: Understanding Ionic Dyes: Ionic dyes (acid dyes, basic dyes, direct dyes) rely on ionic bonds to attach to the fiber. This means the fiber must have suitable chemical groups that can form these bonds.
Step 2: Fiber Chemistry and Dye Affinity: Wool, Silk, and Casein: These are all protein fibers. Proteins contain amino and carboxyl groups, which can form ionic bonds with acid and basic dyes. Polypropylene: Polypropylene is a hydrocarbon polymer. It has no polar or ionic groups. Therefore, it has no affinity for ionic dyes. It can only be colored using specific techniques like melt coloration (adding pigment during fiber production) or using modified polypropylene with dye sites.