By Products & Grading of Cotton

After picking, cotton is sent to gin where the seeds are separated and the fibers are pressed into the 500 pounded forces, ready for sale. The long fibers separated by ginning shall be used for textile manufacturing. These long fibers are called lint. The very short fibers (0.25 inch)) remain with the seed are called linters and used in the manufacturing of human-made cellulosic/regenerated cellulosic fibers e.g. viscose rayon, coprammonium, acatate triacetate, tect. However, there are some byproducts of cotton as below:

· Seed: used in making oils and the residues are used in making soaps, glycerin, etc.

· Hulls: used in making fertilizers and paper.

· Linters: Used in rayon and acetate production, film and plastic production as well as in bank notes manufacturing. It is also used in making blanket, gauge and in pillow.

Grading of Cotton:

In order to grade the quality of raw cotton, the rating (in the order of excellent to poor) is done according to the level of the length, strength, color, luster and impurities of the fibers. These are divided in different ways according to the production land.

Fibers are classified according to their quality. The classification of fibers is called grading. The grading is done basing on the following three factors:

1. Color

2. Foreign matters

3. Preparation of the fibers.

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macro-structure of cotton fiber | Under a microscope cotton

Under a microscope a cotton fiber appears as a very fine, regular fiber, looking like a twisted ribbon or a collapsed and twisted tube. These twists are called convolutions there are about sixty convolutions per centimeter. The convolutions give cotton an uneven fiber surface, which increases inter-fiber friction and enables fine cotton, yearns of squatted strength to be spun. The appearance of the cotton fiber’s cross sections is referred as being kidney-shaped. The micro structure of cotton The cotton fiber is a single plant cell. Its cross-section is oval, compared with the normal hexagonal plant cell. Cotton has a district cuticle, well developed primary and secondary walls and a lumen. Layer 1 the cuticle is a waxy protective layer that provides water resistance to the fibers as they are growing. This lawyer is removed by scouring during processing before spinning.

Importance of twisted structure of textile fiber

Trelor in his Mather lecture, titled “Twisted Structures” adequately recognizes the role of twist in yarns and the part it plays in the design of textile structures .He discusses the obvious necessity of twist in the natural and staple fibers by pointing out “ Twist is essential to provide a certain minimum coherence between fibers, without a yarn having a significant tensile strength cannot be made. This coherence is dependent on the frictional forces brought into play by the lateral pressures between fibers arising from the application of a tensile stress along the yarn axis. With the introduction of continuous filament yarns, however, the role of twist must be reconsidered. In continuous filament yarns, twist is not necessary for the attainment of tensile strength (in fact, it reduces it) but it is necessary for the achievement of satisfactory resistance to abrasion, fatigue, or other types of damage associated with stresses other than a simple tensile stress, and typified ...

Types of Yarn twist | different types of yarn twist | S twist | Z twist

Types of Yarn twist different types of yarn twist S twist Z twist“S” TWIST: A single yarn has “S” twist if when it is held in the vertical direction , the fibers inclined to the conform in direction of slope of the contact portion of the letter “S”. axis of the yarn “Z” TWIST. A single has “Z” twist if when it is held in the vertical direction, the fibers inclined to the yarn axis conform in the direction of the slope to the central portion of the letter “Z”. DIRECTION OF TWIST: In the designation of yarns, it is essential to specify the direction of twist. Besides its importance in simplifying the trade, it is of great technical importance in designing fabrics. For example, in a twill fabric, the direction of twist in the yarn is of particular importance in determining the predominance of twill effect. For a right-handed twill, the best contrasting effect will be obtained when a yarn with Z twist is used; on the other-hand a left-handed twist will produce a fabric ha...

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