2.

2 Cotton Cotton is a soft, staple fiber that grows in a from known as a boll around the seeds of the cotton plant, a shrub native to tropical and sub tropical regions around the world, including the Americas, India and Africa. The fiber most often is spun into yarn or thread and used to make a soft, breathable textile. Cotton is the oldest and the most important of the textile fibers. It has been used in the East and Middle East for thousands of years and was found in use in America when the continent was discovered. Despite the increase variety of manufactured fibers available to the textile industry, demand for cotton remains high because of its suitability on the basis of price, quality and comfort across a wide range of textile products.

Fig : 3 2.2.1 Fiber Morphology 2.2.1.1 The Macro-Structure of Cotton

Fig : 4

Under the microscope, a cotton fiber appears as a very fine, regular fiber, looking a twisted ribbon or a collapsed and twisted tube. Theses twists are called convolutions. There are about sixty convolutions per centimeter. The convolutions give citton an uneven fiber surface, which increases inter-fiber friction and enables fiber cotton yarns of adequate strength to be spun.

Fig : 5

Fig : 6

The appearance of the cotton fibers cross section is referred as being kidney-shaped (Fig:06). These convolution and kindly- shaped cross section of cotton fiber contributes :

 Random contact with the skin which is more compatible with human skin physiology and therefore more comfortable. Increase the moisture absorbency due to the countless minute air spaces because of these convolutions & kidney-shape and thus husk make more comfortable to wear. Cotton fibers are amongst the finest in common use. They have a length from about 10 mm to 65 mm, depending upon the quality and diameter in range from about 11m to 2m. The fiber length to breadth ration of cotton ranges from about 6000 1 to 350 1 . The greater the ration, the more readily can the cotton fibers be spun into yarn. Moreover, yearns from greater fiber length (i.e. Sea Island and Egyptian Cotton) shows more luster. 2.2.1.2 The Micro-structure of Cotton Cuticle The cotton fiber is a single plant cell. Its cross section is oval. Compared with the normal hexagonal plant cell. Cotton has distinct cuticle, well developed primary and secondary walls and a lumen.

Fig : 7 : A morphological diagram of cotton fiber The cuticle is very outside of skin of the cotton fiber. It is composed of a waxy layer (cotton wax) only a few molecules thick. Primary cell wall The primary cell wall, which is immediately underneath the cuticle, is about 200 mm thick and composed of very fine threads of cellulose, called fibrils which are 20 mm think (their length is yet unknown). The fibrils spiral about 70 to the fiber axis ; hence the primacy cell wall can be visualized as a sheath of spiraling fibrils. This spiraling imparts strength of primary cell wall. Secondary cell wall The secondary cell wall, beneath the primary cell wall, forms the bulk of the fiber. Like the growth rings of trees, concentric layers of spiraling cellulosic fibrils of about 10 nm think and undefined length, make up the secondary cell wall. The spiral angle is about 2030 to the fiber axis and widens to about 20-45 nearer the lumen.

Lumen The hollow canal, running the length of the fiber, is called the lumen; its walls are the innermost, concentric layovers of spirals of the secondary cell wall. The lumen was once the central vacuole of the growing cotton fiber and full of cell sap, which is composed of dilute, aqueous solutions of proteins, sugars, minerals an cell wall. The lumen was once the central vacuole of the growing cotton fiber and full of cell sap, which is composed of dilute, aqueous solutions of proteins, sugars, minerals and cell-waste products. When the sap evaporated, its constituents contribute the color of the cotton fiber, and the less inside pressure than the atmosphere resulting is kidney-shaped cross-section of the cotton fiber. 2..2.2 The Polymer System of Cotton The cotton polymer is a linear, cellulose of (65-70)% crystalline and correspondingly (3035) % amorphous. The repeating unit in the cotton polymer is cellubiose which consists of two glucose units. Its degree of polymerization (DP) is about 5000. It is about 5000 nm in length and about .8 nm thick.

Fig : 8 : The chemical structure of cellulose polymer, cottons cellulosic fiber of DP 5000 The most important chemical group on the cotton polymer are the hydroxy1 groups (-OH), which are also present as methylol groups (-CH2OH). Their polarity gives rise to hydrogen bonds between the OH-groups of adjacent cotton polymer. Less significant Van der walls forces also occur. 2.2.3 Chemical Composition of Raw Cotton Cotton fiber are composed of mostly a-cellulose. The noncellulosices are located either on the outer layers (cuticle and primary cell wall) or inside the lumens of the fibers whereas the secondary cell wall is purely cellulose. The specific chemical compositions of cotton fibers vary by their varieties, growing environments (soil, temperature, pet etc) and maturity. Typical composition of raw cotton. Relative Component Main Location Amount (%) Cellulose Secondary wall 86.8 Oils, Waxes Cuticle .7 Pectins Primary Wall 1.0 Carbohydrates Primary Wall .5 Proteins Lumen 1.2

Salts Water Other

Lumen -

1.0 6.8 2.0

During manufacture of cotton materials, they are boiled with solutions of NaOH, which serves to emulsify waxes, hydrolyze fats and proteins and solubilize mineral salts. Some low molecular weight non-cellulosic carbohydrates are also removed. This alkaline treatment gives a loss in weight of around 7%. The oil and waxes of cotton consists of (a) Glycerides, which are readily specifiable oils and fats. (b) Waxes, which are saponified with difficult oils and fats. (c) Unsaponifiable oils. (d) Free fatty acids and (e) Traces of soaps. 2.2.4 Fiber properties Fiber length Specific Gravity Dry Tenacity (g/denier) Wet Tenacity (% of Dry) Tensile Strength (PSIx10+) Elongation at Break (%) Elastic Recovery (% Recovery) Stiffness (g/denier) Moisture Regain Refractive Index : : : : : : : : : : 1-5 cm 1.54 3.0-4.9 100-110 60-120 3-11 75-45 57-60 7.0-8.5 1.54

Others
Resiliency Abrasion Resistance Dimensional Stability : : : Low Mediam Mediam

2.2.4.1 Chemical Properties of Cotton Effect of acid Cotton is weaken and destroyed by the effect of acids; hydrogen the glucoside linkage of oxygen atom. Concentrated Nitric acid, for short time, cause some shrinkage and increase strength and dye ability.

Effect of alkali Normally resistant, when boiled in presence of O2, oxycellulose form. Treatment with 20% NaOH increase strength and dye ability. Liquid ammonia treatment increase strength, elongation etc. Both of solution is used as mercerizing liquor. Effect of bleach All kinds of bleaching agents have its action on cotton. NaOCI and Na-per borate are common. H2O2 is least harmful. Effect of organic solvent Cotton is resistant of organic solvent. So dry wash is possible. Effect of heat Conductive ironing temperature150C. Decompose at 240C. Ignition temperature 39C. Effect of sunlight Affected by infrared cause deteriorates color becomes yellow. Dry ability Azoic, Direct, Reactive Sulphur and Vat dyes are applicable to cotton substrates. Attack by moth No. Attack by mildew Untreated not easily but starches and gums increase activities.

Uses of Cotton Cotton is used to number of textile products. These include terrycloth, used to make highly absorbent bath towels and robes; denim, used to make blue jeans, chambray popularly used in the manufacture of blue work shirts (from which we get the term blue-collar) and corduroy, seersucker, and cotton twill, socks, underwear and most T-shirts are made from cotton. Bed sheets often are made from cotton. Cotton also used to make yarn used in crochet and knitting. Fabric also can be made from recycled or recovered that otherwise would be thrown away during the spinning. Weaving or cutting process. While many fabric are made completely of cotton, some materials blend cotton with other fibers, including rayon and synthetic fibers such as polyester. It can either be used in knitted or woven fabrics, as it can be blended with elastine to make a stretcher thread for knitted fabrics and apparel such as stretch jeans. In addition to the textile industry, cotton is in fishnet. Coffee filters, tents, gunpowder (see Nitrocellulose), cotton paper, and in bookbinding. The first Chinese paper was made of cotton fiber. Fire hoses were once made of cotton.

The cotton seed which remains after the cotton is ginned is used to produce cotton seed oil. This, after refining, can be consumed by human like any other vegetable oil. The cotton seed meal that is left generally is fed to ruminate livestock; the gossypol remaining in the meal is toxic to monastic animals. Cotton seed hulls can be added to dairy cattle rations for roughage. During the American slavery period, cotton root bark was used in a folk remedy as an abortifacient, that is to provoke abortion. Cotton linters are fine, silky fibers which adhere to the seeds of the cotton plant after ginning. These curly fibers typically are less than 1/8 in (3mm) long. The tern also may apply to the longer textile fiber staple lint as well as shorter fuzzy fibers from some upland species. Linters are traditionally used in the manufacture of paper and as a raw material in the manufacture of cellulose. Shiny is a processed version of the fiber that can be made into cloth resembling stain fir shirts and suits. However, its hydrophobic property of not easily taking up water makes it unfit for the purpose of bath and dish towels (although examples of these made from shiny cotton are seen). The term Egyptian cotton refers to the extra long staple cotton grown in Egypt and favored for the luxury and up market brands worldwide. During the U.S Civil War, with heavy European investment, Egyptian-growing cotton became a major alternate source for British textile mills. Egyptian cotton is more durable and softer than American Pima cotton, which is why it is more expensive. Pima cotton is American cotton that is grown in the southwestern states of the U.S. In South Asia, cotton is widely used in mattresses, which are the most common type of mattress used in that region.