Question

Which dye is responsible for tendering of cotton?

• A. Reactive dye
• B. Basic dye
• C. Sulphur dye
• D. Azoic dye

Hint:

Associate specific problems with dye classes: - Sulphur Dyes \(\rightarrow\) Tendering (acid formation). - Vat Dyes \(\rightarrow\) Phototendering (certain yellow/orange dyes can degrade fiber in sunlight). - Azoic Dyes \(\rightarrow\) Poor rub fastness (surface deposits). - Direct Dyes \(\rightarrow\) Poor wash fastness.

Answer 1

The Correct Option is C

Step 1: Understand "tendering." Tendering refers to the loss of strength or degradation of a textile fiber, making it weak and brittle.

Step 2: Analyze the chemistry of the dye classes in relation to cotton.
- Reactive dye: Forms a stable covalent bond with cotton and does not cause degradation.
- Basic dye: Used for acrylics, has no affinity for cotton unless it's mordanted. Not typically a cause of tendering on cotton.
- Sulphur dye: These dyes contain sulphur linkages. During storage, especially under humid and acidic conditions, some sulphur can slowly oxidize to form sulphuric acid. This acid attacks and hydrolyzes the cellulose of the cotton fiber, causing a severe loss of strength (tendering). Sulphur black is particularly notorious for this issue.
- Azoic dye: Formed in-situ. Does not typically cause tendering. Conclusion: Sulphur dyes are well-known to be responsible for the tendering of cotton during storage due to the potential formation of sulphuric acid.