ASTM D6720-07

This test method is considered satisfactory for acceptance testing of commercial shipments because current estimates of between-laboratory precision are acceptable and the method is used extensively in the trade for acceptance testing.

5.1.1 If there are differences of practical significance between reported test results for two laboratories (or more), comparative tests should be performed to determine if there is a statistical bias between them, using competent statistical assistance. As a minimum, use samples for such comparative tests that are as homogeneous as possible, drawn from the same lot of material as the samples that resulted in disparate results during initial testing, and randomly assigned in equal numbers to each laboratory. The test results from the laboratories involved should be compared using a statistical test for unpaired data, at a probability level chosen prior to the testing series. If bias is found, either its cause must be found and corrected, or future test results for that material must be adjusted in consideration of the known bias.

This test differs from other crimp contraction test methods in that it measures the recoverable stretch during the unload cycle of the yarn.

1.1 This test method covers the determination of the recoverable stretch of commercial textured yarns, covered elastomeric yarns and other stretch yarns using skeins. This test method is particularly valuable for yarns that develop additional crimp upon exposure to hot, wet conditions. The recoverable stretch is a relative measure of the recovery power the yarn can be expected to provide in a finished fabric.

1.2 This test method is applicable to continuous filament yarns and is suitable for yarns that develop additional stretch potential upon exposure to heat.

1.3 This method is applicable to yarns 500 denier or finer.

1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for information only.

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.