Question

Carriers are used in the dyeing of:

• A. Silk
• B. Wool
• C. Nylon
• D. Polyester

Hint:

Carriers are used when dyeing polyester at \( 100^\circ\text{C} \) under atmospheric pressure.
In modern industrial dyeing, high-temperature high-pressure (HTHP) systems at \( 130^\circ\text{C} \) are preferred.
These systems eliminate the need for carriers by using thermal energy to swell the fibers.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Textile dyeing requires dye molecules to diffuse into the amorphous regions of the fiber matrix.
Some synthetic fibers have highly crystalline structures with high glass transition temperatures (\( T_g \)).
These fibers require chemical auxiliaries or high temperatures to facilitate dye penetration.

Step 2: Detailed Explanation:
Polyester is a highly synthetic, hydrophobic fiber characterized by a tight, highly crystalline structure.
Because of this structure, water-soluble dyes cannot easily penetrate the fiber.
Polyester is dyed using disperse dyes, which are non-ionic and hydrophobic.
When dyeing polyester at boiling temperatures under atmospheric pressure, chemical auxiliaries called carriers are added to the dye bath.
These carriers (typically organic compounds like orthophenylphenol, biphenyl, or chlorinated benzenes) temporarily swell the polyester fiber structure.
This swelling action increases the molecular free volume within the fiber, allowing the disperse dye molecules to penetrate the fiber matrix.
In contrast, natural protein fibers like silk (A) and wool (B), and synthetic polyamide fibers like nylon (C), have more open structures and do not require carrier assisted dyeing.
Therefore, carriers are used in the dyeing of polyester.

Step 3: Final Answer:
Carriers are chemical swelling agents used in the dyeing of Polyester.