Influence of Fiber Fineness and Maturity in spinning Process

Influence of Fiber Fineness and Maturity on spinning Process

Fiber Fineness

Fiber fineness determine how many fibers are present in the cross section of a yarn of given thickness. Additional fibers in the cross section not only provide additional strength but also a better distribution in the yarn. Minimum 30 fibers are needed, usually over 100 fibers are required. Fiber fineness influences spinning limit, drape of the fabric, yarn strength, luster, yarn evenness, handle, yarn fullness and productivity. Productivity is influenced by reduced end breakage rate.

In a conventional spinning process, fine fibers accumulate to the core and coarse fibers in the periphery.

Fiber fineness is measured in dtex which is equal to ratio of mass in dgrams and length in km. Decitex is equal to the product of Micronaire value of the cotton and 0.394.

Cotton fibers are generally classified as very fine if they have a micronaire value upto 3.1; fine if they have value between 3.1 to 3.9; medium if they have it between 4.0 to 4.9; slightly coarse between values of 5 to 5.9 and coarse if they have a micronaire value above 6.

Fiber Maturity

Cotton fiber consists of cell wall and lumen. The maturity index depends upon the thickness of the cell wall. The fibers are considered ripe if they have maturity index between 50-80 percent, unripe if they have MI between 30 to 45% and dead when they have it less than 25%.

Unripe fibers have neither adequate strength nor adequate longitudinal thickness. They lead to loss of yarn strength, neppiness, high proportion of short fibers, varying dyeability, processing difficulties mainly at the card.

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Why Wool Feels Warm

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Why Wool is Warm to Wear- Heat of Sorption

When a fiber absorbs water, heat is evolved. It results from the attractive forces between the fiber and water molecules. The phenomenon occurs due to the fact that when moisture vapour is absorbed into fiber’s internal structure, it transforms from gas to liquid and the phase change produces the rise in temperature.

It is calculated by heat of wetting. It is the heat evolved when a specimen of the material at a given regain, whose dry mass is one gram is completed is completed wetted.

It is expressed in joules per gram ( of dry material)

The heat of wetting is greatest for the more highly absorbing fibers and is very small in the non-hygroscopic fibers. Thus it is 113 J/g for wool, 106 for viscose, 69 for silk, 55 for flax, 46 for cotton , 73 for mercerized cotton and only 34, 31,5 and 7 respectively for Acetate, Nylon, Polyester and Acrylic.

As we can see from the figures above, wool has the highest heat of sorption. And this heat raises the temperature of the wearer which makes the wool feel warmer. In fact “the heat of sorption from a kg of Merino can be equivalent to the output from an electric blanket over eight hours” (Source ).

You can also find some discussion on Heat of Sorption here.

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