Elastane

Elastane is never processed on its own; it is always in the fabric alongside another fibre. Its role is therefore not to set the recipe but to narrow its limits.

How does elastane constrain the recipe?

Elastane is a polyurethane-based fibre that owes its stretch to soft segments in its chemical structure. Those segments are sensitive to heat, alkali and chlorine. Once damaged, the fabric loses its recovery and does not get it back.

The share in the fabric is usually small, but it is what governs the recipe:

• Temperature. Long exposure to high temperature reduces recovery; time on the stenter matters as much as the setting.
• Alkali. Strong alkaline conditions break down the elastane chain, which is why bleaching on cotton-elastane is kept moderate.
• Chlorine. Pool water attacks elastane; chlorine-resistant types are specified for swimwear.

What changes on polyester-elastane?

Disperse dyeing runs near 130 °C, which is at elastane's ceiling. Cycle time is shortened, and heating and cooling are controlled.

Reduction clearing after dyeing calls for alkali, and that is limited on elastane blends. Special-purpose washing agents that work near neutral are used instead. See the polyester page.

Why are oil stains a bigger problem on elastane blends?

Elastane carries oil from yarn production and from the knitting machine. That oil does not stay on the surface; it penetrates the fibre, and because alkali and temperature are limited it is not fully removed by ordinary washing conditions.

If it is not taken out before dyeing, the dye behaves differently there and the stain appears on dyed goods. Oil stain removers are a family of their own; the choice between solvent-based and solvent-free types weighs effluent against the fabric's limits.

Finishing and handle

Finishing does two things on elastane blends: it builds handle and it reduces needle friction during sewing. Silicone emulsions are used for this; elastomeric types give surface lubricity without restricting stretch.

Emulsion stability matters especially here: a broken silicone emulsion spots the fabric, and on elastane blends that spot cannot be stripped. Choosing a silicone softener compares the types.

Which product groups are used on elastane blends?

Washing agents and oil stain removers, wetting agents, dispersing and levelling agents, antifoaming agents and finishing agents.