Fineness is one of the three most important fibre characteristics.
The fineness determines how many fibres are present in the cross-section of a yarn of given thickness. Additional fibres in the cross-section provide not only additional strength, but also a better distribution in the yarn.
Thirty fibres are needed at the minimum in the yarn cross-section, but there are usually over 100.
Fibre fineness influences primarily:
Drape of the fabric product
Productivity of the process.
Why Fiber Fineness is so important:
It has been known since long that fibre fineness plays an important role in determining the quality of resultant yarn and hence that of the resultant fabrics. In general fiber fineness is important due to the following factors:
1. It affects Stiffness of the Fabric
As the fiber fineness increases, resistance to bending decreases.
It means the fabric made from yarn of finer fiber is less stiff in feel.
It also drapes better.
2. It affects Torsional Rigidity of the Yarn
Torsional rigidity means ability to twist.
As fiber fineness increases, torsional rigidity of the yarn reduces proportionally.
Thus fibers can be twisted easily during spinning operation.
Also there will be less snarling and kink formation in the yarn when the fine fibers are used.
3. Reflection of Light
Finer fibers also determine the luster of the fabric.
Because there are so many number of fibers per unit area that they produce a soft sheen.
This is different from hard glitter produced by the coarser fibers.
Also the apparent depth of the shade will be lighter in case of fabrics made with finer fibers than in case of coarser fibers.
4. Absorption of Dyes
The amount of dye absorbed depends upon the amount of surface area accessible for dye out of a given volume of fibers. Thus a finer fiber leads to quicker exhaustion of dyes than coarser fibres.
5. Ease in Spinning Process
A finer fiber leads to more fibre cohesion because the numbers of surfaces are more so cohesion due to friction is higher.
Also finer fibers lead to less amount of twist because of the same increased force of friction.
This means yarns can be spun finer with the same amount of twist as compared to coarser fibers,
6. Uniformity of Yarn and Hence Uniformity in the Fabric
Uniformity of yarn is directly proportional to the number of fibres in the yarn cross section.
Hence finer the fiber, the more uniform is the yarn. When the yarn is uniform it leads to other desirable properties such as better tensile strength, extensibility and luster.
It also leads to fewer breakages in spinning and weaving.
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