Disperse dyes are small, almost water-insoluble dye molecules that are applied as a fine dispersion. They are the main dye class for polyester, and they also dye acetate, triacetate and, with some limits, nylon and acrylic.
If you buy dyes for polyester fabric, polyester yarn or polyester blends, you are buying disperse dyes.
How they work
Polyester is hydrophobic and tightly packed. At high temperature the fibre opens up, and the dye moves from the bath into the fibre, where it stays as a solid solution. Most polyester is dyed at about 130°C under pressure, or by the thermosol process, where dye is padded on and fixed with dry heat.
Because the dye sits in the fibre as a dispersion, the quality of the dispersion matters. Poor milling or the wrong dispersing agent can cause spots, filtering on yarn packages and uneven shades.
Energy levels
Disperse dyes are often grouped by energy level, which tells you how they behave in dyeing and how fast they are to heat:
- Low-energy dyes dye quickly at lower temperatures but have weaker sublimation fastness.
- Medium-energy dyes are a balance and suit most exhaust dyeing.
- High-energy dyes need higher temperatures but resist sublimation, which suits thermosol dyeing and heat-set fabrics.
Points to check when buying
- Ask for the physical form, since powder, granule and liquid forms behave differently in your plant.
- Ask for sublimation and wash fastness results on polyester, not only light fastness.
- Confirm the dye is free of restricted disperse dyes and banned amines, since some older disperse dyes are known sensitisers. See how dyes are tested for banned amines.
- Compare strength against your current standard, not against the seller's claim, as explained in how dye strength is measured.
Where disperse dyes are used
Polyester is the largest synthetic fibre, so disperse dyes go into a very wide range of goods. Sportswear, fashion fabrics, curtains, upholstery, car seat fabrics and polyester sewing thread all rely on them. Car interior fabrics need dyes with very high light fastness under heat, and makers sell special ranges for that use.
Disperse dyes are also used in sublimation transfer printing, where dye is printed on paper and transferred to polyester with heat. That use needs low or medium energy dyes that sublime cleanly, and the ink-grade products are milled much finer than standard textile grades.
For polyester and cotton blends, mills use disperse dyes for the polyester part and reactive dyes for the cotton. Ask your supplier whether its disperse dyes stain cotton and how easily that stain clears in reduction clearing.
Next step
Gujarat has many disperse dye makers, and dispersion quality varies between them. We find and audit plants, check samples against your standard and have lots tested. To compare suppliers, book a free sourcing review.