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Acrylic

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INTRODUCTION AND MANUFACTURING

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Acrylic

  1. 1. TM 1051
  2. 2. Introduction In 1940, DuPont manufactured acrylic from Acrylonitrile. According to FTC; Fibers spun from polymers consisting of at least 85 % by weight of acrylonitrile units (CH2CHCN)
  3. 3. Raw material: Vinyl acetate Acrylic monomer Ammonium sulphate Sodium bisulphite
  4. 4. Polymerization Ammonium sulfate and sodium bi sulfhite are dissolved in demineralized water at 40 degree centigrade A mixture of acrylonitrile monomer and vinyl acetate monomer are added slowly with stirring for a period of 2 hours The reaction is exothermic Monomers are soluble in water but polymer is not The air is replaced by inert gas like (ammonia)
  5. 5. Polymer is separated as slurry from the solution The slurry is withdrawn and washed until it is free from salts and then dried
  6. 6. Spinning: Polymer powder is dissolved in solvent- dimethyl formamide A delustring agent is added during polymer preparation It is then filtered and then immediately used for spinning
  7. 7. Dry spinning: After filtration of polymer, it is heated to boiling point and then extruded through spinneret The fine jets of solution emerge into vertical tube through which air is flowing at high temperature (400 degree centigrade is flowing) As jets fall through the tube, the solvent evaporate and leave solid filaments of polymer
  8. 8. The filaments are stretched 3-10 times original length in this hot state The continuous filaments are spun and collected on bobbin with speed at about 1000-1200 m/min Filaments yarn are made in 75-200 denier range For manufacture of staple fibers continuous filaments are washed, are crimped and cut into lengths 1.5-2 inch
  9. 9. Wet spinning: Polymer is dissolved in solvent and then fed to spinneret It is then pumped through spinneret in a coagulating bath in which solvent is soluble but polymer is insoluble the jets of solution coagulates into fine filaments
  10. 10. The filaments are passed over steam heated rollers at 100-110 degree centigrade and rotating at high speed Stretching is carried out at 4-10 times to their original lengths the filaments are crimped and then cut into various staple length
  11. 11. Properties Tenacity: For staple fiber: Dry: 2-3.6 g/denier Wet: 1.6- 2.7 g/denier For filament: Dry: 4.0-4.1 g/denier Wet: 3.0-3.8 g/denier Tensile strength: Staple: 30,000-45,000 lb/sq inch Filaments: 50,000- 75,000 lb/sq inch
  12. 12. Elongation: Staple fiber: 20-55 % Filament: 30-36% Elastic recovery: 90-95 % recovery at 1% stretch 50-60% at 10% stretch Specific gravity: 1.16-1.18 Effect of moisture: 1-3% the water absorption is low
  13. 13. Thermal properties: they tend to stick to metal surface at 215-255 degree centigrade Effect of sunlight: Excellent resistance to sunlight and after almost 600 hours exposure, tenacity of fiber is 96% of original tenacity
  14. 14. Effect of Acids: they are unaffected by dilute solutions of strong acids but are affected by concentrated solutions Effect of Alkalis: Only strong alkali attack fiber e.g. NaOH Insects: they are not attacked by micro-organisms
  15. 15. End uses: Used for apparel, knitwea, Blankets, and carpets

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