Question

Two cotton fibre varieties A and B having linear density of 3.2 and 4 (microgram/inch) respectively are tested on air flow instrument. The highest flow rate is obtained in case of

• A. Fibre A with maturity ratio 0.9
• B. Fibre B with maturity ratio 0.9
• C. Fibre A with maturity ratio 1.0
• D. Fibre B with maturity ratio 1.0

Hint:

In air flow testing, higher fibre fineness gives lower flow, while coarser and mature fibres give higher flow readings.

Answer 1

The Correct Option is D

Step 1: Principle of air flow instrument.
Air flow instruments measure fibre fineness indirectly by allowing air to pass through a compressed fibre plug. Coarser and more mature fibres create larger inter-fibre spaces, allowing higher air flow.
Step 2: Effect of linear density.
Fibre B has a higher linear density (4 microgram/inch) compared to Fibre A (3.2 microgram/inch), making Fibre B coarser. Coarser fibres permit greater air flow.
Step 3: Effect of maturity ratio.
A higher maturity ratio (1.0) indicates thicker cell walls and better fibre development, which increases the effective fibre diameter and air permeability.
Step 4: Combined effect.
The combination of higher linear density and higher maturity produces the maximum air flow.
Step 5: Conclusion.
Hence, the highest flow rate is obtained for Fibre B with maturity ratio 1.0.

Answer 2

An air flow (porous-plug) instrument reads fineness indirectly: for a fixed weight of fibre packed into the test chamber, coarser and more mature fibres leave larger, more open channels between them, so air passes through more easily and the flow rate reading is higher. Checking each option against this rule identifies the case with the highest flow rate.

1. Fibre A, maturity 0.9: Fibre A is the finer of the two (linear density 3.2 microgram/inch), so it packs into smaller, more numerous inter-fibre spaces even before maturity is considered. This combination gives one of the lower flow rates among the four cases.
2. Fibre B, maturity 0.9: Fibre B is coarser (4 microgram/inch) than Fibre A, which favours a higher flow rate, but a maturity of only \(0.9\) means the fibre wall is not as fully developed as it could be, so the flow rate, while better than Fibre A's, is not the maximum possible for Fibre B.
3. Fibre A, maturity 1.0: Full maturity improves wall development and rigidity, but Fibre A's linear density is still the lower of the two, capping how coarse the effective fibre bundle can be. Coarseness dominates over maturity here, so this case still trails behind a fully mature Fibre B.
4. Fibre B, maturity 1.0: This combines the higher linear density (coarser fibre, larger inter-fibre channels) with full maturity (well-developed, thicker fibre walls), so both factors that raise air flow are maximised together.

Since coarseness and maturity both independently raise the flow rate, and Fibre B at maturity 1.0 has the best of both, it gives the highest reading.

Therefore, the correct answer is Fibre B with maturity ratio 1.0.