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Dyeing processes

Polyester-nylon knit dyeing process: disperse dyeing, reduction clearing and acid dyeing

Polyester-nylon is dyed in two baths, polyester first with disperse dye, then nylon with acid dye. Here is the process from our floor, step by step.

Kamrul Islam Textile engineer · 14+ years in dyeing
Updated 2 min read
Polyester-nylon knit dyeing process: disperse dyeing, reduction clearing and acid dyeing

Polyester-nylon is dyed in two baths, polyester first with disperse dye, then nylon with acid dye. Here is the process from our floor, step by step.

At a glance

180°CHeat set, always

130°CPolyester bath

100–110°CFinishing

No enzyme

Polyester-nylon knits are dyed in two baths: the polyester part with disperse dye, the nylon part with acid dye, each following its own single-fibre process.

The route for polyester-nylon

Process flow: polyester-nylon knit dyeing

Start: greige fabricfrom knitting
Greige inspectionholes, yarn faults, GSM
Batchingone lot per batch; turned inside out if it stays a tube
Slittingopen width: never heat set, singed or mercerised as a tube
Heat settingopen, 180°C
Back sewinginto a tube, face side inside
Load hot80°C × 10 min
Scourno bleach
Disperse dyeingpolyester part, pH 4.5, 130°C
Reduction clear
Acid dyeingnylon part, 40 → 98°C
Softenerthen unload
Finishingstenter 100–110°C
End: finished fabric
GreigePreparationDyeingAfter-treatmentFinishing
Two baths: polyester first, then nylon. No enzyme. Dashed steps run only when the fabric needs them.
  1. Heat setting of the greige fabric at 180°C, always.
  2. Scour only, the same as nylon-elastane.
  3. Polyester part: disperse dyeing at pH 4.5, following the polyester process.
  4. Reduction clearing.
  5. Nylon part: acid dyeing following the 100% nylon process.
  6. Softener, and unload. With no cotton or viscose in the fabric, there is no reactive soaping or fixing step.
  7. Finishing at 100–110°C.
  • Polyester-nylon gets the same scour and the same process as nylon-elastane. No enzyme.
  • It is always heat set, at 180°C, the same as nylon-elastane.
  • The polyester bath is 130°C. We do not lower it because of the nylon: where there is polyester, 130°C is needed.
  • Where there is no cotton or viscose, the soaping and fixing are not needed: reduction clearing and a good softener.

The polyester bath runs at 130°C, the same as 100% polyester. It is not lowered because of the nylon: as long as there is polyester in the fabric, even a small share, it needs 130°C to take the disperse dye. Heat setting is at 180°C, the same as nylon-elastane.

The dyeing curves

Bath 1, polyester part: disperse dyeing (polyester-nylon)
Load hot at 80°C × 10 min, pH 4.5, dye dosed over 30 min, 1°C/min to 130°C, 45 min hold, cool at 1°C/min to 78–80°C. Then drain and reduction clear.
Acid dyeing, nylon part (polyester-nylon)
The nylon curve: 40°C start, 0.5°C/min from 50°C to 98°C with a 10 min hold at 70°C, 50 min at 98°C, pH sliding down as the acid donor releases acid.

Finishing

Fabric with polyester is finished at 100–110°C on the stenter and compactor, not at the 140–150°C used for cotton. Hotter than that, the disperse dye moves back to the fibre surface and the fastness fails.

Kamrul Islam
Kamrul Islam

Textile engineer with 14+ years in dyeing and fabric development. He writes every guide on Dyeing Solution from real production work. Full profile

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