Fibre Science And Technology

Step 1: Understanding DMF as a solvent.
Dimethyl formamide (DMF) is a strong polar aprotic solvent capable of dissolving certain synthetic polymers when heated to its boiling point.
Step 2: Behaviour of acrylic fibres.
Acrylic fibres, primarily composed of polyacrylonitrile, are soluble in DMF at elevated temperatures. Hence, DMF is commonly used as a solvent for acrylic polymers in fibre manufacturing and testing.
Step 3: Eliminating other options.
Nylon 6 and Nylon 66 are polyamides and are not dissolved by DMF under normal conditions. Wool is a natural protein fibre and is insoluble in DMF.
Step 4: Conclusion.
Therefore, DMF at boiling temperature acts as a solvent for acrylic fibres.

Step 1: Understanding nylon nomenclature.
The number in nylon (e.g., Nylon-4) indicates the number of carbon atoms present in the monomer unit used for polymerisation.
Step 2: Identifying the correct monomer.
Nylon-4 is produced by ring-opening polymerisation of 2-pyrrolidone (commonly written as 2-pyrrolidine in some texts). It contains four carbon atoms in the repeating unit.
Step 3: Eliminating incorrect options.
Dodecalactum is used for Nylon-12, and amino undecanoic acid is used for Nylon-11.
Step 4: Conclusion.
Hence, Nylon-4 is made by the polymerisation of 2-pyrrolidine.

Step 1: Understanding decortication.
Decortication is a mechanical process used to separate fibres from the fleshy or woody part of plant leaves or stems. It involves scraping, crushing, and beating actions.
Step 2: Fibre-specific application.
Sisal fibres are obtained from the leaves of the Agave plant. These leaves contain fibres embedded in fleshy tissue, which must be removed mechanically.
Step 3: Eliminating other options.
Jute and ramie fibres are extracted mainly by retting, not decortication. Wool is an animal fibre and does not involve such a process.
Step 4: Conclusion.
Hence, decortication is related to sisal fibre extraction.

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.

Step 1: Understanding polynosic fibre.
Polynosic fibre is a modified viscose rayon with higher crystallinity and molecular orientation compared to regular viscose.
Step 2: Effect on strength.
Due to improved structural order, polynosic fibres exhibit higher tenacity than ordinary viscose rayon.
Step 3: Typical tenacity values.
The standard tenacity range of polynosic fibres lies between 3.5 and 4.5 g/den.
Step 4: Conclusion.
Hence, the correct tenacity range of polynosic fibre is 3.5--4.5 g/den.

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.