Question

The twist per inch (TPI) of a yarn primarily affects its:

• A. Fineness
• B. Strength
• C. Length
• D. Moisture regain

Hint:

Yarn strength increases with twist up to an optimum level; beyond that point, excessive twist can reduce strength due to fibre damage.

Answer 1

The Correct Option is B

Step 1: Understanding twist per inch (TPI).
Twist per inch (TPI) refers to the number of turns inserted into a yarn per inch length. Twist binds the individual fibres together, improving cohesion and resistance to slippage under applied force.
Step 2: Effect of twist on yarn properties.
As the twist increases, fibres become more tightly packed, increasing inter-fibre friction. This enhances the yarn’s ability to withstand tensile forces, thereby increasing its strength up to an optimum twist level.
Step 3: Analysis of options.
(A) Fineness: Fineness depends on fibre diameter and yarn count, not directly on twist.
(B) Strength: Correct — Twist significantly influences yarn strength by improving fibre cohesion.
(C) Length: Yarn length is independent of the amount of twist inserted.
(D) Moisture regain: Moisture regain depends on fibre type and environmental conditions, not twist.
Step 4: Conclusion.
Since twist directly improves fibre binding and resistance to breakage, the property primarily affected by TPI is yarn strength.