Question

During drawing crystallinity of a fibre

• A. Increases
• B. Decreases
• C. Remains same
• D. May change in any direction

Hint:

Drawing improves fibre strength by increasing molecular orientation and crystallinity.

Answer 1

The Correct Option is A

Step 1: Understanding fibre drawing.
Drawing is a process in which fibres are stretched to several times their original length. This aligns the polymer chains along the fibre axis.
Step 2: Effect on molecular arrangement.
During drawing, the initially disordered amorphous chains become oriented and pack more closely together, promoting the formation of crystalline regions.
Step 3: Effect on crystallinity.
As molecular alignment improves, crystallinity increases due to better chain packing and enhanced intermolecular bonding.
Step 4: Conclusion.
Hence, crystallinity of a fibre increases during drawing.

Answer 2

Drawing stretches a fibre to many times its original length, and the question is what this mechanical stretching does to how tightly the polymer chains are packed and ordered. Testing each option against the physics of stretching a long-chain polymer settles it.

1. Increases: Stretching pulls the long polymer chains, which were tangled and randomly coiled in the as-spun fibre, into straighter, more parallel segments. Straighter, parallel chains can approach each other closely enough for regular, repeating packing to form, which is exactly what a crystalline region is, so more such regions form as drawing proceeds.
2. Decreases: This would require drawing to disorder the chains further, but pulling a chain straight is the opposite of randomizing it; tension aligns chains rather than tangling them, so a decrease is inconsistent with what stretching physically does.
3. Remains same: This would only be true if drawing had no effect on chain arrangement at all, but drawing is deliberately used in fibre manufacture precisely because it changes chain orientation and packing; if it had no effect, this processing step would serve no purpose.
4. May change in any direction: This would apply if the outcome depended unpredictably on unspecified conditions, but the mechanical effect of uniaxial tension on a long-chain polymer is consistently to align and straighten chains, giving a predictable, one-directional outcome.

Since drawing consistently straightens and aligns chains, allowing tighter, more ordered packing, the crystalline fraction of the fibre goes up.

Therefore, the correct answer is Increases.