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Silk pretreatments

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Silk pretreatments Silk pretreatments Presentation Transcript

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