The tensile strength of fibre varies for 50, to 1,25, pounds per square inch. Fine cottons tend to have greater tensile strength than the short and coarse cottons. Convolutions Twists The uniform distribution of the convolutions helps to give better inter- fibre grippage. Convolutions confer the following additional advantages Make the fibre equally flexible in all directions. Prevent close packing of fibres in yarn and hence give better cover in cloth. As the frictional contact of adjacent fibres is reduced, it lessens the risk of electrification, if any.
The number of convolutions depends on the ratio of cell-wall thickness to ribbon width. The number of convolutions per inch varies from about for Indian cottons to about for Sea Island cottons. Surface Friction The spinning quality of a textile fibre depends not only on its staple length and fineness, but also in its ability to offer sufficient frictional resistance. The effectiveness of friction depends upon the nature of the fibre surface and normal pressure between fibres due to twist.
Hygroscopicity Cotton absorbs moisture from the surrounding atmosphere depending on its temperature and relative humidity. Moisture had a marked effect on the tensile strength, elasticity and other properties of the fibre. Rigidity In processing cotton, the fibres have to be twisted to make a yarn. The more rigid a fibre is, the greater is the force required to twist it and vice versa. Modules of rigidity is defined as the ratio of the tangential force per unit area to the angle of twist produced.
It depends upon the shape of cross section and the wall thickness of the fibre. Temperature and relative humidity have a great influence on fibre rigidity.
At room temperature, the rigidity of cotton fibre is six times that in an atmosphere saturated with moisture. Elasticity Changes in length and volume as well as shears or twists produced by applied stresses are all included in the elastic properties. Cotton fibres are fairly elastic, though they exhibit both the primary creep and the secondary creep to some degree.
Plasticity Cotton is relatively non- plastic. Finishing process like shrinking depend on the increase in the plasticity of cotton fibres as they swell in water at elevated temperatures. Cotton quality requirements Count-wise Pattern of Yarn Production The main trends observed from data given. Yarn production in coarse counts 1s to 10s has come down during recent years. The production in fine and superfine counts 41s and above has increased during the years.
The production in the 31s' - 40s' count range has also increased during recent years. The above trends indicate that while attention has to be given for producing cottons suitable for finer counts, greater efforts have to be made to produce cottons suitable for the count ranges of 11s to 40s.
Blending with Man-Made Fibres Although the preference for cotton in apparel fabrics is increasing as against fabrics made from purely synthetic fibres, the use of blends of cotton and synthetic fibres is expected to continue for various reasons. Prior to , imported cottons from Egypt, Sudan, etc. Our cottons, however, need improvement in respect of fibre maturity and trash content.
Cottons used for blending should have good fibre strength and extensibility. Deficiencies in fibre quality There are a few important deficiencies that add to lowering the quality of our cottons. Variability in Fibre Quality A frequent complaint both from Indian and foreign users of our cottons is about the variability in quality observed even in the same lot of cotton. Some zoning system along with supply of good quality seeds and other inputs may have to be considered at least for superior quality varieties and hybrids like MCU 5, Hybrid 4, Hybrid 6, DCH 32 etc, Fibre Strength for OE Spinning open end As has been stated earlier, fibre strength plays a very important role in deciding the yarn quality in OE spinning system.
Cotton and cotton textile industries are central to the economic growth of both developed and developing countries, and contribute to development that is sustainable and socially responsible. Cotton is the raw material of wealth, industrialization and development. It is a vital cash crop providing income for everything from education, health and housing to transportation, and often serves as a catalyst for industrialization and rising social welfare.
World cotton production and consumption are trending higher, and the industry is being transformed by new technologies, including biotechnology. Printer-Friendly Version. How Cotton is Ginned and Marketed. Today, nearly all cotton is stored in modules, which look like giant loaves of bread. Modules allow the cotton to be stored without loosing yield or quality prior to ginning. Specially designed trucks pick up modules of seed cotton from the field and move them to the gin. An equity sale can be made to a cotton merchant prior to harvest for a specified number of bales at a fixed equity above the loan value.
Upon receipt of the cotton, PCCA places it in the CCC loan program, receives the equity payment and transfers the option to redeem the cotton to the merchant who will ultimately decide when the CCC loan is repaid.
Another type of sale is for a fixed price where PCCA collects the full cash value at the time of invoice for cotton not in the CCC loan. The third type of sale is an unfixed on-call transaction usually made directly with textile mills.
PCCA fixes the basis value above or below a specific cotton futures contract, and the buyer chooses the futures price when it reaches the desired level to complete the transaction. To manage its risk, PCCA offsets these sales by selling futures contracts. Due to the potential impact of weather on cotton yields and quality, forward sales are carefully managed and are the first to be filled when bales are invoiced. After forward sales are filled, the marketing staff begins sending recaps to its commissioned agents around the world.
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