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Lecture 7

CTD 215 Lecture 7: Textiles Chapter 7 Notes

5 Pages
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Department
Clothing, Textiles and Interior Design
Course Code
CTD 215
Professor
Dr.Thompson

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Description
Textiles Chapter 7 Notes Manufactured Regenerated Fibers Identifications of Regenerated Fibers • Manufactured regenerated fibers: From naturally occurring polymers; regenerated fibers. • Cellulosic: Rayon, lyocell, and acetate • Protein: Azlon Rayon • First manufactured fiber. Production began in France in 1890, “Chardonnet Silk” was the name given to the fiber. • Bemberg process introduced in later 1890’s, Viscose process introduced around 1900. • U.S. production began in 1910, in Marcus Hook, Pennsylvania. World’s leading producer today are Toray (Japan), Lenzing (Austria) and Courtaulds (Great Britain) . • Rayon is regenerated cellulose; starting material is purified, bleached wood pulp. Chemicals are added to the cellulose to convert it into a derivative which can be dissolved to form a viscous polymer solution (viscose). • The viscose is extruded through gold or platinum spinnerets immersed in an acid bath (wet spinning). The cellulose derivative is decomposed by the acid in the bath and cellulose is regenerated, as continuous filaments. • These filaments are stretched, washed and dried, then either packaged as continuous filament material or chopped into short staple fibers. Chemical Composition and Molecular Arrangement of Rayon • Rayon: Manufactured fiber of regenerated cellulose in which substitutes have replaced not more than 15% of the hydrogens of he hydroxyl groups. Viscose Process • Raw material – wood pulp, bleached & purified or cotton linters (pure cellulose) • Soak (steep) in strong alkali – to yield alkali cellulose, the dp is reduced ~ 300 (cotton is 6,000-10,000) • Add carbon disulfide to produce sodium cellulose xanthate (like an orange crumb) • Dissolve product in dilute alkali • Solution obtained has the appearance and consistency of honey • Solution is called viscose • Blending, ripened, deaerated, pigments, delusterants added. • Pump through gold or platinum spinnerets into sulfuric acid bath (wet spinning) • Cellulose is regenerated, but in filament fiber form ~ 40% crystalline. • In US, this is a staple fiber (continuous filament made to be cut into staple fiber is called tow) • Environmental issues ➢ Generated hydrogen sulfide gas ➢ Sulfuric acid waste • Modified rayon ➢ High-tenacity rayon o Zinc compound o Slow regeneration while stretched  more oriented and crystalline ➢ High-wet-modulus rayon o Greater resistance to deformation when wet due to greater chain length than regular rayon o In Europe, trade names for improved rayons are Modal and polynosic rayon Properties of Viscous Rayon • Physical ➢ White, striations along surface, crenulated cross section (star shape) • Mechanical ➢ Low dp, low crystallinity  low tenacity, lower wet tenacity ➢ Stretch but has a low elastic recovery, low resilience  wrinkles ➢ Weakens when wet – loses 50% of strength • Chemical ➢ More amorphous: more absorbent, high regain, high dyeability ➢ Lower ironing temperature, more susceptible to acids and bases • Other ➢ Subject to mildew, silverfish ➢ Weakened by sunlight ➢ Shrinks; very low abrasion resistance Rayon • Appearance retention: moderate ➢ Regular: poor resiliency, progressive shrinkage ➢ HWM: less wrinkling, accepts durable press & dimensional stability finishes, can be mercerized • Care: ➢ Regular: limited washability (wrinkling, loss of sizing, excessive shrinkage), dry clean ➢ HWM: greater washability, less wrinkling, shrinkage may be controlled Lyocell • Lyocell is a fiber generic classification approved by the FTC in 1996 • Fiber production began in 1991 on a pilot-plant scale by Courtlaulds; the fiber is now in full production by Courtaulds as Tencel lyocell. Lenzing produces Newcell lyocell. • Starting material is purified, bleached wood pulp. This is dissolved in a special solvent, NMMO. NO reduction in DP is required. • N –methyl-morpholine-N-oxide, amine oxide • Polymer solutions extruded through spinnerets into water baths, and the fiber forms by coagulation in the non-solvent system (wet spinning). The
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