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| Cotton fibers view under microscope. |
Cotton is a natural fiber (vegetable fiber) obtained from the seed of the cotton plant. Chemically, cotton is a polysaccharide or polymeric sugar that is represented by the chemical formula (C6H10O5)n. For most apparel and home end uses, cotton fiber is particularly well suited because of its combination of strength, durability, and comfort properties. Cotton also has good temperature resistance, which is important in textile-mill dyeing and finishing processes and consumer care.
Cotton, fibers are the seed hairs of the plant Gossypium. They are usually off-white in colour although some varieties have been bred to incorporate a natural colour. Each fiber is formed by the elongation of a single cell from the surface of the seed. The word cotton is derived from it’s Arabic name pronounced kutan, qutn or qutan depending on the dialect. 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.
Almost half of the world’s requirements for textile fibers are met by cotton. It is grown in many parts of the world where a hot dry climate is to be found, the main producers being USA, the former USSR, China, India, Egypt, Africa and South America. Cotton consists typically of between 88 to 96% cellulose with the rest being protein, pectic substances (congealed gum-like carbohydrates), ash and wax. After scouring and bleaching, cotton is then about 99 % cellulose. The fibers are weakened and destroyed by acids but are resistant to alkalis. The fiber length varies with the type and quality, within the range 10 to 65 mm; the fiber diameter ranges from 11 to 22 μm. Cotton is a relatively strong fiber with a strength of 25 to 35 cN/tex and a breaking elongation of 7 to 9 %. It is stronger when wet. Cotton also absorbs moisture readily, which makes cotton clothes comfortable to wear in warm weather (water retention of 50 %, moisture regain of 7 %). Cotton fiber burns readily and is not inherently resistant to oxidising agents, and biodegradation, as well as acids. Despite these shortcomings cotton has a good wear life. Its properties can also be readily modified by chemical finishes which provide enhanced performance, e.g. crease resistance and flame resistance. It is used in both 100% form and in blends with other fibers for household textiles and apparel.
Cultivation of Cotton
Cotton is a plant of the genus Gossypium, which includes 32 species, several of which produce cotton fibers. The cottons native to Asia are primarily G. arboreum and G. herbaceum, and U.S. cottons are principally G. barbadense and G. hirsutum. G. barbadense includes the long-staple Pima, Egyptian, and Sea Island cotton varieties, and G. hirsutum is upland cotton.
Cotton fiber is produced on the plant in bolls. Each boll is composed of 3 to 5 locks of fiber adhering to seeds. Each lock can have 7 to 9 seeds, and a single seed can have 10,000 to 20,000 fibers. Thus, a 5-lock boll of fiber can have a half million fibers. Fiber production depends on the plant variety, region, nutrients, weather, and other related factors such as damage by insects, bacteria, or fungi.
Cotton fiber from the field is composed of 87 % to 90 % cellulose and 5 % to 8 % water, the remainder being natural impurities. The cellulose content increases with fiber maturity. Large proportions of immature cotton fibers can result in various types of problems in textiles. The moisture content of cotton varies depending on storage conditions, and the amounts and types of impurities vary depending on growth region, fertilizer, and variety.
Ginning of Cotton
The purpose of the cotton gin is to mechanically separate the cotton fiber from the seed. Ginning is also used to remove non-cotton materials from the lint. If done too aggressively, ginning can increase the short-fiber content within a bale. After ginning, the fibers are compressed into cotton bales weighing from 480 to 500 pounds (210 to 220 kilograms). The bales are then shipped to textile mills, where they are spun into yarns for fabrication or shipped to non-woven textile facilities for web formation.
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USES OF COTTON: Cotton is known for its versatility, performance and natural comfort. It is used to make all kinds of clothes and homewares as well as for industrial purposes like tarpaulins, tents, hotel sheets and army uniforms. Cotton fibre can be woven or knitted into fabrics such as velvet, corduroy, chambray, velour, jersey and flannel. In addition to textile products like underwear, socks and t-shirts, cotton is also used in fishnets, coffee filters, book binding and archival paper. Cotton is a food and a fibre crop. Cotton seed is fed to cattle and crushed to make oil. This cottonseed oil is used for cooking and in products like soap, margarine, emulsifiers, cosmetics, pharmaceuticals, rubber and plastics.
Cotton linters are the very short fibres that remain on the cottonseed after ginning. They are used to produce goods such as bandages, swabs, bank notes, cotton buds and x-rays.
PROPERTIES AND COTTON PRODUCTS
-Cotton is both a food and fibre crop.
-The cotton plant produces fruit, known as bolls.
-When mature the crop is picked and ginned - which separates the cotton fibre (or lint) from the seed.
-Cotton lint makes up about 42 percent of the picked cotton by weight, and contributes about 85 percent of the total income from a cotton crop. The other -15 percent of income is from cotton seed.
-Almost all parts of the cotton plant are used in some way including the lint, cottonseed, linters, stalks and seed hulls.
Natural cotton fibre properties
-Cotton is a soft, absorbent and breathable natural fibre, making it the perfect fibre for clothing and undergarments worn close to the skin
-Cotton keeps the body cool in summer and warm in winter because it is a good conductor of heat
-Cotton is non-allergenic and, unlike synthetic fibres, cotton fibre is a natural product that contains no chemicals
-Cotton, due to its unique fibre structure, breathes better and is more comfortable than oil-based synthetic fabrics
-Cotton is one of the easiest fabrics to dye due to its natural whiteness and high rate of absorbency
-Cotton in particular is perfectly suited to colour application processes as it offers spinners crisp white lint, low breakages and stoppages, good throughput efficiency and uniformity of yarn
-Cotton holds up to 27 times its own weight in water and becomes stronger when wet
-Cotton can’t hold an electric charge, eliminating static cling
Cotton is used for virtually every type of clothing, from coats and jackets to foundation garments. Most of its apparel usage, however, is for men clothing. Cotton supplies over 70 % of this market, with jeans, shirts and underwear being major items.
In home furnishings, cotton’s uses range from bedspreads to window shades. It is by far the dominant fiber in towels and washcloths, supplying almost 100 % of home furnishingsthat market. Cotton is popular in sheets and pillowcases, where it holds over 60 % of the market. Industrial products containing cotton are as diverse as wall coverings, bookbindings and zipper tapes. The biggest cotton users in this category, however, are medical supplies, industrial thread and tarpaulins.
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