Silk pretreatments


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Silk pretreatments

  1. 1. Silk pretreatment R.B.Chavan Department of Textile Technology Indian Institute of Technology Hauz-Khas, New Delhi 110016
  2. 2. Silk worm fed on Mulberry leaves
  3. 3. Silk fibre <ul><li>Silk is protein fibre </li></ul><ul><li>It consists of solidified viscous fluid excreted from the glands of silk worm </li></ul><ul><li>When the silk worm is matured it consists large number of these glands. The liquid comes out from each gland in the form of fine stream </li></ul><ul><li>As soon as it comes in contact with air it is solidified in the form of fine filament. </li></ul><ul><li>The filaments are wrapped in the oval shape due to spinning of the silk worm during the excretion of the fluid. </li></ul><ul><li>This is known as silk cacoon in which silk silk worm eventually get enclosed </li></ul>
  4. 4. Silk cacoon
  5. 5. Silk Reeling
  6. 6. Silk yarn in hank form
  7. 7. Silk weaving
  8. 8. Silk cocoon <ul><li>One Coccon may contain 300 meters of silk multi filament </li></ul><ul><li>1000 cocoons may be required to get 100 gm of silk filament yarn. </li></ul><ul><li>The spinning of cocoon takes 304 days </li></ul><ul><li>When it is complete the silk worm get converted into pupa which remains inside the cocoon </li></ul><ul><li>The silk filament is surrounded by ntural gum known as silk gum </li></ul><ul><li>Both silk and gum are proteins </li></ul><ul><li>Seracin Silk gum protein </li></ul><ul><li>Fibroin Silk fibre protein </li></ul><ul><li>Seracin is more amorphous and easily attacked by chemicals </li></ul>
  9. 9. Silk Varieties <ul><li>Mulberry silk </li></ul><ul><li>Tussar silk </li></ul><ul><li>Eri </li></ul><ul><li>Muga </li></ul><ul><li>Category </li></ul><ul><li>Cultivated silk (Mulberry) </li></ul><ul><li>Wild silk (Tussar, Eri, Muga) </li></ul><ul><li>Indian states </li></ul><ul><li>Karnataka, Madya pradesh, Assam, Jharkhand </li></ul><ul><li>Countries </li></ul><ul><li>China, India, Japan, Thialand </li></ul><ul><li>Most expensive fibre </li></ul><ul><li>Queen fibre </li></ul><ul><li>Luxurious feel and shine </li></ul>
  10. 10. Silk composition <ul><li>Mulberry silk </li></ul><ul><li>Fibroin 70-75% </li></ul><ul><li>Sericine 25-30% </li></ul><ul><li>Waxy substances 2-3% </li></ul><ul><li>Natural colours 1-1.5% </li></ul><ul><li>Mineral matter 0.5-1% </li></ul><ul><li>Added impurities Lubricants and softener used during weaving and oil stains </li></ul>
  11. 11. Silk pupa
  12. 12. Silk Degumming <ul><li>Degumming or Boiling off: Removal of silk gum (Sericine) without damaging the silk (Fibroin) </li></ul><ul><li>Presence of gum </li></ul><ul><li>No lustre </li></ul><ul><li>Brown colour </li></ul><ul><li>Harsh feel </li></ul><ul><li>Removal of gum </li></ul><ul><li>Lustrous appearance of silk </li></ul><ul><li>Soft feel </li></ul><ul><li>Sericene acts as protective coating during weaving it removal is carried out after weaving unless the silk dyeing is required in yarn from. </li></ul>
  13. 13. Gum Content <ul><li>Mulberry silk 25-30% </li></ul><ul><li>Tussar 5-15% </li></ul><ul><li>Muga 7-10% </li></ul><ul><li>Eri 3-5% </li></ul>
  14. 14. Fibroin and sericin <ul><li>Both fibroin and sericin are proteins, Insoluble in water </li></ul><ul><li>Sericin is more amorphous and easily attacked by chemicals. </li></ul><ul><li>Fibroin is cystalline and more resistant to chemicals </li></ul><ul><li>It is possible to remove sericin without damaging silk protein (fibroin) </li></ul><ul><li>Degumming is usually carried out under mild alkaline conditions using soap </li></ul><ul><li>Traditionally olice oil soap known as Marseille soap is used. </li></ul><ul><li>The alkalinity of soap and its detergency action not only hydrolyze sericin but also remove natural waxes and oil stains. </li></ul><ul><li>Sometimes sodium bicarbonate or sodium carbonate (pH 10) is used along with soap. </li></ul>
  15. 15. Degummimg with soap <ul><li>Marseille soap (olive oil soap) 25% owm </li></ul><ul><li>Temperture 90-95 deg. C </li></ul><ul><li>Time 1-2 hours </li></ul><ul><li>Wash with hot and cold water to remove hydrolyzed gum </li></ul><ul><li>Loss in weight 25-28% depending on extent gum removal </li></ul>
  16. 16. Enzyme degumming <ul><li>Proteiase enzymes cn break the peptide/amide linkages and convert them into simple amino acids </li></ul><ul><li>Trypsin (Serin protease) preferntially attack sericin </li></ul><ul><li>Two steps </li></ul><ul><li>First Step </li></ul><ul><li>Treat with 0.5- g/l enzyme , 55-60 deg. C, 30 min. to remove sericn </li></ul><ul><li>Second step </li></ul><ul><li>To remove natural waxes and oil stains </li></ul><ul><li>Treatment with Soap and 1 g/l soda ash, 95 deg. C 20 min. </li></ul>