The difference between reactive vs disperse dyes comes down to fibre. Reactive dyes bond chemically to cellulose fibres such as cotton, viscose and linen. Disperse dyes are fine, water-insoluble particles that dissolve into polyester, acetate and other synthetic fibres.
Choosing the wrong class gives weak, uneven colour that washes out, so the fibre decides before anything else.
Which fibres take reactive dyes?
Reactive dyes form a covalent bond with the hydroxyl groups in cellulose, which gives bright shades and good wash fastness. They are used on cotton, linen, viscose and other cellulosic fibres, and also on wool and silk with suitable chemistry.
The dye needs alkali and salt in the dyebath, and some of it hydrolyses and washes off. That is why wash-off and effluent load matter in reactive dyeing. The class is covered in what reactive dyes are.
Process conditions also differ. Reactive dyeing is done at moderate temperature with salt and alkali, and the dye is fixed by reaction. Polyester dyeing with disperse dye usually needs high temperature and pressure, or a carrier, followed by a reduction clearing step to remove surface dye. If a supplier cannot tell you the recommended conditions for its product, that is a sign it may be reselling, not making. Ask for application recommendations in writing along with the data sheet.
Which fibres take disperse dyes?
Disperse dyes are used for polyester, which is by far their main use, and also for acetate, triacetate and nylon. They are applied from a fine dispersion in water, usually at high temperature and pressure for polyester.
Because the dye sits inside the fibre rather than bonding to it, heat can move it later. Sublimation fastness is therefore a key property for polyester. See what disperse dyes are.
Remember that dyes sold under similar names can differ in hue, strength and fastness. When changing supplier, run a lab dip on your own fabric and process before bulk dyeing, and keep the approved dip as the reference. This is cheap to do and avoids the costly surprise of a full batch dyed in the wrong shade.
What about blends such as polyester-cotton?
A blend needs both classes, because neither dye colours the other fibre. Polyester-cotton is usually dyed with disperse dye for the polyester and reactive dye for the cotton, either in two baths or in a controlled one-bath process.
The two dyes must be chosen to match in shade and fastness, otherwise the fabric looks different under different light. Ask your dye supplier for recommended pairs, not just individual products.
What should you check when buying either class?
The checks are broadly the same for both classes:
- Strength against a reference standard, as explained in dye strength.
- Shade difference between batches, within an agreed tolerance.
- The fastness properties your customer requires, such as wash, light, rubbing and sublimation.
- The form: powder, granule or liquid, which affects dissolving and dust.
- Restricted-substance compliance, such as banned amines and heavy metals, for your end market.
Next step
Write the fibre, process and target fastness into the specification before asking for quotes. We find and audit dye makers in Gujarat, check samples and have lots tested. Book a free sourcing review to start with your fibre and shade list.