Narrow Elastics
Elongation sells the tape; permanent set is what comes back as a complaint. Both come off the same specimen in one test.
— %
Share of the imposed extension that is recovered
Elastics are rate- and cycle-dependent: quote the extension rate, the hold time and the cycle number with the result, or two labs will not reproduce each other. Medical compression products are decision-support only here — confirm against the applicable compression standard.
Elastic Stretch, Recovery & Modulus Calculator — free, with the formula and a worked example, at Textile School.