COTTONIntroduction Cotton is a natural vegetablefibre produced in the cottonplant in many countries of theworld Cotton is widely used TextileFiber in Textile Industry, dueto its versatile uses.Types of CottonThe following species are grown commercially: Gossypium arboreum L. Tree cotton, native to Indiaand Pakistan. Gossypium barbadense L. known as American Pima,Creole, Egyptian, or Sea island cotton, native to tropicalSouth America. Gossypium herbaceum L. Levant cotton, native tosouthern Africa and Arabian Peninsula. Gossypium hirsutum L. Upland cotton, native toCentral America, Mexico, the Caribbean and southernFlorida - most commonly grown species in the world. Gossypium peruvianium Gossypium purpurascadePolymer System Cotton polymer is a liner, cellulose polymer. The repeating unit is cellobiose which consists of two glucose unit. Cotton consists of 5000 cellobiose units therefore degree ofpolymerization is 5000. polymer length is about 5000nm andthickness is 0.8 nm. Cotton is a semi-crystalline fibre; crystalline regions are 65-70 %while amorphous regions are 30-35 %. Hydrogen bonding are the dominant and most important forces ofattraction between polymeric chains. OH,-CH2OH give rise to hydrogen bonds. The polymeric system can be imagined as roll of wire netting.Fibre MorphologyMacro structure Cottonappear as fine, regular fibre with little variation in diameter;its diameter is not considered as critical as length. The fibre lengthto breath ratio is 6000:1 for finer and long cotton and 350:1 forshortest and coarser cotton type. Its length is from 10mm-65mm. Range in fibre diameter is from 11m 10 22 m. Cotton color varies form near white to light tan. The colour dependsupon cotton type, soil, environmental and climatic conditions underwhich it is grown. Under microscope cotton looks like ribbon or twisted tube. Thesetwists or convolutions classified cotton under the microscope. Convolutions are formed after the cotton ball burst open. Cotton cross-section appears under the microscope as kidneyshape.Longitudinal ViewCross-Sectional ViewMicro Structure of Cotton Cotton fibre is a single plant cell. It hasdistinct cuticle, well developed primary andsecondary walls, and a lumen. Cuticle is the outside or skin of fibre. it iscomposed of waxy layer (cotton wax) a fewmolecule thick. The primary cell wall is about 200 nm thick.It is composed of 20 nm thick fibrils; spiral at70 to the fibre axis. Beneath the primary wall lies secondary wallmade of concentric layer of spiraling fibrils;this forms the bulk of the fibre. Fibrils areabout 10 nm thick and spiral at about 20 30 to the fibre axis near the primary wall.This spiral angle widen to about 20 - 45 forthe fibril layer near the lumen. The hollow canal running the length of thefibre is called Lumen. Its walls are innermost concentric layers of fibrils of secondarywall. The lumen was once full of cell sap.Properties of Cotton1. TenacityStrength comes from the good alignment of polymer, formation ofhydrogen bonds between polymer chains, and spiral fibril in secondaryand primary wall.Cotton gain strength when wet due to further improvement in chainalignment and formation of hydrogen bonds with 5% increase in tenacity.2. Elastic natureCotton is inelastic due to high crystalline structure and for this reason Itwrinkle and creases readily. When its wet the hydrogen bonds breaksand reformation of hydrogen bonds at new place prevent cotton recovery.3. Hygroscopic natureCotton is absorbent due to polar group OH in its structure; this attractwater. That gives better penetration of dyes, chemicals and wettingagent. The plus point is that the hygroscopic nature prevent fibre fromstatic electric electricity.4. Thermal propertiesCotton can with stand hot ironing. Excessive application of heat causecotton fibre to char and burn without any prior melting. This indicate thatcotton is not thermoplastic.Properties of Cotton5. Chemical properties Cotton get weakens and destroyed by acids. Acidic conditions hydrolysis.Mineral and inorganic acids hydrolyze cotton more readily than organicacids. Cotton fibres are resistant to alkalis and are relatively unaffected bylaundering due to lack of attraction between cotton polymer and alkalis. The most common bleach used is hydrogen peroxide. Sodium per borateis commonly available In laundry detergent which is effective above 50. Effect of sunlight and weather Effect of sunlight and weatherUltra violet rays of sunlight provide photochemical energy whileinfrared rays provide heat energy to degrade the cotton fibre In thepresence of moisture, atmospheric oxygen and air pollutants. Airpollutants are acidic and may cause degradation of cotton through acidhydrolysis. Colour Colour fastness fastnessCotton dyes are direct, reactive, vat, azoic and sulphur dyes.Various Finishes of Cotton Mercerization- adds strength, improves lustre,absorbency, dyeability Sanforization-ensures less than 1 % shrinkage Moireing- for variable luster and variable pattern Glazing-gloss, smoothness and embossedeffects Stiffening- smoothen, stiffens and strengthens Wrinkle resistant permanent press- improvesshape-retension and imparts dip-drycharacteristic Schreinerizing-adds lusterVarious Finishes of Cotton Stain repelling-for easy care Napping-for softness, warmth and increasedabsorbency Singeing-for smoothness Weighting-for bulk Insulating-for warmth Embossing-for decoration Mildew resistant Fire-retardant Moth-resistantAdvantages of Cotton It can be processed into a wide selection of fabrics :- Sheer fabrics - cambric, batist chiffon, lawn, organdy and voile. Medium weight cottons- broadcloth, drill, flannel, poplin, terrycloth and long cloth. Heavy weight cottons - brocade, corduroy, denim, pique andvelveteen. Can be mercerized to improve luster, absorbency, dyeability andstrength. Textured effects are easily achieved by :- Changing yarn structure - high twist yarns, nub yarns, bouclyarns, crimped yarn. Changing fabric construction - crepes, serersuckers. Application of special finishes - embossing and napping. Can be easily dyed or printed with almost all classes of dyes. Good absorbent, Does not build up static electricity, Good conductorof heat.Limitations of Cotton Untreated cotton wrinkles easily Susceptible to mildew if left damp Flammable Takes a long time to dryCotton Ginning The freshly picked seed cotton; is separated from seeds throughGinning procedure. The separated cotton is then called Gin Cotton. Cotton Gin is of two types1. Roller Gin2. Saw Gin The main body of an operating part is a roll 1m thick and 25cm indiameter. While saw gin has round saw of same diameter,containing 50-80 teeth approximately 15mm apart. After removing raw cotton the short cotton called linter remain on theseed which is further removed from the seed through linter collectormachine similar to Saw Gin. Cotton linter is used for substances like Bamberg, celluloid, andcotton gun power. The percentage of collecting Gin cotton from seed is 25 50%, theportion of Linter cotton is 6-10% of Ginned cotton.Roller GinSaw Gin