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Pigments are the colouring agents that are insoluble in the medium from which they are applied and that must be added to fibre spinning solutions or must be attached to the surface of the textiles by resin binders.
Materials used as pigments include both organic and inorganic compounds.
Actually they are not true dyes because they have no affinity for the fibre and are applied and held to the fabric with resins, which are then cured at high temperatures.
The colours confined to light shades, bright colours, and such metallic colours as gold etc.
Pigment dyeing gives excellent light fast colours and generally with good all around fatness. However if the shade is too deep, the colour will crock.
Greater improvement in the pigments and resins has made it possible to dye in much darker shades than was possible at first.
Although economical to use and simple to apply, pigment colours may not be colour fast to laundering and dry-cleaning.
Suitability for textiles:
- Pigment dyes are usually applied to cotton cloth but are also used on fabrics of wool and manmade fibres.
- Used primarily for printing cotton of all weights; also wool, rayon, acetate, nylon, polyester and olefins.
Method of application:
Pigments are colouring agents that are insoluble in the medium from which they are applied and that must be added to the fibre spinning solutions or must be attached to the surface of the textiles by resin binders. Materials used as pigments include both organic and inorganic compounds. Insoluble azo and vat dyes; inorganic salts such as cobalt, aluminates, cadmium sulphide and copper arsenate and materials such as carbon black may be used as pigments.
Pigment colours are used in solution dyeing of acetate, rayon, nylon, polypropylene, polyester, glass and other man made fibres. The olefin fibres both polypropylene and polyethylene frequently are coloured with pigments because the fibres are difficult to dye by other means. When pigment colours are added to the fibre solution or molten polymer the term dope dye, mass pigmentation and solution dye are used. Fibres coloured in this manner exhibit good colour fatness to laundering, dry cleaning, light, perspiration, crocking and abrasion.
Pigments have no affinity for fibres. To fix them on fabrics some type of adhesive, resin or bonding agent must be employed. The colours may be dispersed and padded in to the fabric or they may be printed on to the fabric surface. Fabrics made of glass fibres are usually printed with pigment colours. The colours are relatively permanent, except in the case as the resin wears away the colour also disappears. A stiff, harsh hand may be evident on pigment-printed fabrics.
Fastness properties:
- Textile materials dyed with pigment dyes have very good to excellent light fastness.
- Materials dyed with pigment colours have good wash fastness properties.
- Pigment dyed textiles have good fastness to sea water, perspiration and staining.
- Majority of the textiles dyed with pigment dyes are not susceptive to gas fading but a few are sensitive to gas fading.
- Pigment dyed textiles have good fastness to crocking for light to medium shades, very poor fastness to crocking for dark shades.
- Pigment dyes may not be colour fast to laundering and dry cleaning.
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