TEXTILE INDUSTRIESCHE 432INDUSTRIAL PROCESS

HistoryFibers originally from wool, silk, cotton, flax and similar materials1883: 1st man-made fibers by Swan when he squirted a solution of cellulose nitrate in acetic acid through holes1885: 1st commercial fibers from cellulose nitrate by Chardonnet1892: viscose production patented1900: cuprammonium rayon fiber made1921: cellulose acetate fiber1940: 1st synthetic fiber nylon (polyamide) discovered by Carothers, commercialised by DuPontMid 1950s: polyesters, acrylics, polyolefins produced as well

Uses And EconomicsMan-made fibers 45% of worlds fiber productionUses depends on nature of individual fiberClothing, carpets and upholstery made of synthetic fibersShirt & garments blends of polyester and cotton Nylon in US for carpet production

Properties Of FibersGeneral properties: length, crimp & denierEither continuous filament or short fibers, uniform in length, spun into threadShort fibers cotton & wool called stapleContinuous filaments infinite length, most synthetic fibers & natural silkSynthetic staple fibers prepared by cutting continuous filaments to short, uniform lengths usu. betw. 3.5-15 cmCrimp curl or waviness placed in synthetic fibers by chemical or mechanical actionDenier measure of weight of fibers per unit length & defined as weight in grams of 9000 m, another unit is tex weight of 1000 m1st synthetic fibers were circulate, but special characteristics imparted by manufacturing fibers with non-round cross sectionMost fiber in the market have filaments whose cross section are not uniformly round

Synthetic FibersClassification:Manufacture begins with preparation of polymer consisting of very long, chain-like moleculesPolymer spun and results in weak useless fiber until it is stretched to orient molecules and set up crystalline latticesBy controlling within limits degree of orientation, crystallinity, and average chain length, single polymer can be used to make a no. of fibers with widely differing mechanical properties ranging from weak and stretchy to strong and stiff2 important factors to determine mechanical properties of polymer: 1) attractive forces betw. molecules and 2) flexibility & length of molecular chains

Spinning procedures:Melt spinning (nylon, polyester, polyvinyl, polypropylene) involving pumping molten polymer through capillaries or spinnerets, then solidified by quenching in cool airDry spinning (acrylics, vinyl-acrylic) polymer dissolved in suitable organic solvent. Solution forced thru spinnerets, evaporation of solvent in warm air, dry filaments formedWet spinning (acrilan, creslan) spinning of solution of polymer and coagulation of fiber in chemical bath

Table 35.1 Representative synthetic fibers and films

PolyamidesNylon 6,6 : 1st synthetic fiber made commerciallyUsed for home furnishing carpetsPolymerization reaction of adipic acid and hexamethylene diamineFig 35.3 - flow chart for nylon yarn using batch process

PolyestersPolymers of ester formed from dimethyl terephthalate and ethylene glycolPolymerization is a two stage process:1st stage : monomer prepared either by ester interchange between dimethyl terepthalate and EG or by direct esterificaiton of terepthalic acid2nd stage : polymerization of monomer

Fig 35.5 flowchart for polyester fibers production

Acrylics And ModacylicsMajor component of several industrial textile fibers, DuPonts Orlon 1st attained commercial scale operationOrlan made by polymerizing acylonitrileResistance of chemical attack esp. to weathering makes them useful in several fieldsEnd users sweaters, womens coats, mens winter suiting, carpets and blankets. Suitable for pile fabrics and filter cloth

Cellulosic FibersRayon and acetate

Carbon fibersHigh-modulus carbon fibers prepared from rayon, polyacrylonitrile or pitchRayon fibers are charred at 200 350oC & carbonized at 1000 2000oC

Carbon fibers sold in three forms:Low modulus used as electrically conducting surface for electrostatic spraying and injection molding to get electrical conductivity, resistance to heat and improved wear Medium modulus fiber can be formed into fabricsHigh modulus lowest priced high-modulus yarn available and used when stiffness is critical

Carbon fibers reinforcing plastics which can be used for sporting goods (fishing rods) & engineering plastics

Finishing and dyeing of textilesModification of fibers and fabrics by special treatment to change their properties & to improve their usefulness is increasingThree important finishes: 1) flameproofing or fire retarding 2) mildew or rotproofing and 3) water repellencyTemporary flame proofing achieved by application of ammonium salts or borax and boric acidIdeal flame proofing allows cleaining or laundering and but maintain desirable fabric characteristics is difficultMildew proofing obtained by use of organic and inorganic compounds eg. Acrylonitrile, chlorinated phenols To produce water repellent finishes durable to usual cleaning processes, special quarternary ammonium compounds are heat treated onto fiber