This test method for testing loop tension and elongation of elastic fabrics is considered satisfactory for acceptance testing of commercial shipments of elastic fabrics because the test method is used in the trade for acceptance testing.

In case of a dispute arising from differences in reported test results when using this test method for acceptance testing of commercial shipments, the parties should conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test specimens that are as homogeneous as possible and that are from a lot of material of the type in question. The test specimens should then be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using student's t-test for unpaired data and an acceptable probability level chosen by the two parties before the testing is begun. If bias is found, either its cause must be found and corrected or the purchaser and the supplier must agree to interpret future test results with consideration to the known bias.

This test method specifies the use of the CRE-type tensile testing machine. Users of this test method are cautioned that loop tension test data obtained using this method are not comparable to tension test data obtained using Test Method D 1775 because of the differences in testing machines. Test Method D 1775 uses a CRL-type tensile testing machine.

The loop tension and extension relationship of an elastic fabric is an important criterion for judging the suitability of the fabric for various end uses, such as: foundation garments, brassieres, and swimsuits.

Data from loop tension-recovery curves can be compared only if the tension testing machine, rate-of-extension, maximum loading (or extension), and specimen specifications are comparable. Since different machine set-ups will cause different results on the same fabric, machine set-ups must always be specified before making a test and be reported with the test results.

The test for measuring loop tension at specified elongation(s) is used to determine the tension of an elastic fabric when subjected to a specified elongation which is less than the elongation required to rupture the fabric. The test prescribes points of measurement on the extending (outgoing) cycle only.

The test for measuring elongation at specified tension(s) is used to determine the elongation of an elastic fabric when subjected to a specified loop tension which is less than the tension required to rupture the fabric. The test prescribes points of measurement on the loading (outgoing) cycle only.

1.1 This test method covers the measurement of tension and elongation of wide or narrow elastic fabrics made from natural or man-made elastomers, either alone or in combination with other textile yarns, when tested with a constant-rate-of-extension (CRE) type tensile testing machine.

Note 1—For determination of similar testing using the constant-rate-of-load (CRL) type tensile testing machine, refer to Test Method D 1775.

1.2 The use of this test method requires the selection of, or mutual agreement upon, loop tension(s) and elongation(s) at which the test results will be determined.

1.3 Laundering procedures require mutual agreement on the selection of temperature and number of washing cycles and drying cycles to be used.

1.4 The values stated in SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore each system must be used independently of the other, without combining values in any way.

1.5 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.