T400 and T800 Bi-Component Yarns: Stretch Without Elastane
Bi-component polyester yarns give mechanical stretch without elastane, offering dimensional stability and lower cost in the right applications.
What follows is a practical breakdown for sourcing and development teams, from specification through to verification.
How bi-component stretch works
Two polymers of different shrinkage are spun side by side into one filament; helical crimp develops during heat setting.
For most programmes the decision is taken during development, when changing the specification still costs nothing more than one sampling round.
Benefits over elastane
No elastane means no chlorine sensitivity, no elastane fatigue and better dimensional stability over repeated laundering.
Fix the limits for the whole size range, not only for the middle size, as grading changes the numbers involved.
- Ask for a separate price line for the requirement
- Confirm minimum quantities before committing the colourway
- Build one extra approval round into the calendar
Where T400 and T800 fit
Use them in woven bottoms, lightweight jackets and structured knits where moderate rather than high stretch is required.
Log adjustments and their reasons, which turns each production run into useful data for the next one.
Limitations to plan for
Recovery is lower than quality elastane, so very compressive leggings still need a spandex blend.
Repeat the test when the fabric, the mill or the finishing route changes, as previous results no longer apply.
- Confirm the numeric range and the test method in the specification
- Keep an approved physical standard at the machine
- Retest after the agreed care regime before shipping
Processing and specification
Fix crimp development temperature and shrinkage targets, and test elongation in both directions before bulk.
Document what is included in the price, including testing, packing and documentation, to keep comparisons fair.
Summary
A clear specification, a trained operator and a documented test together remove most of the risk from this part of the programme.
