Thursday, 28 January 2016

Dyeing Fabrics - Types of Dye

  • Dyeing is the permanent application of a colourant to a fibre to give a uniform colour
  • The colourant must be able to be absorbed by, or react with, the textile fibre
  • Must be soluble so it can get into the spaces between the fibre molecules
Direct Dyes
  • soluble in water
  • used for viscose, cotton and modal fibres
  • moderate light fastness
  • poor wash fastness
  • salt can be added to help fibres absorb the dye
Reactive Dyes
  • soluble in water
  • forms a strong chemical bond with cellulosic and protein fibres
  • produces bright colours that have good wash fastness
Vat Dyes
  • not soluble in water
  • excellent wash and light fastness
  • can produce indigo dye
  • a lot of indigo dye sits on top of the fibre rather than being absorbed into it, causing it to rub off onto other fabrics and lose some colour when washed
  • to get the dye into the fabric, it has to be converted into a soluble form by removing oxygen
  • once the dye is in the fibre it’s converted back into its insoluble form by oxidation, making the molecules too big to get out of the fibre
Disperse Dyes
  • used to dye fibres with hydrophobic properties
  • almost insoluble in water
  • applied to fibre in the form of a fine aqueous dispersion
  • held inside fibres by chemical bonds
Acid Dyes
  • soluble in water
  • applied to fabric in an acidic dye bath
  • good light fastness
  • wash fastness varies
Solvent Dyes
  • were created as water usage and disposal of dyes in an environmentally friendly way is expensive
  • uses organic solvents instead of water
  • however, solvent dyes are very expensive and there is cost involved in recovering the organic solvent to use again
  • equipment can be expensive
  • not very economical

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