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1.1 This test method covers the determination of the breaking tenacity of wool fibers as a flat bundle with a ¹/₈ in. (3.2 mm) clamp separation.

1.2 This test method is especially adapted to the fiber bundle clamps and strength testing instruments specified, but may be used on other tensile testing machines when equipped with appropriate adapters to accommodate the prescribed clamps.

1.3 This test method is applicable to wool in any form which can be hand-combed into small bundles of parallelized fibers.

1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

5.1 Test Method D2524 for testing wool fibers for tenacity is considered satisfactory for acceptance testing when the participating laboratories, using a reference wool, have shown acceptable between-laboratory precision. It is recommended that any program of acceptance testing be preceded by an interlaboratory check in the laboratory of the purchaser and the laboratory of the seller on replicate specimens of samples of the material to be evaluated. In cases of dispute, the statistical bias, if any, between the laboratory of the purchaser and the seller should be determined with each comparison being based on testing randomized specimens from one sample of material of the type being evaluated.

5.2 Values obtained from flat bundle tenacity show a good correlation with values obtained from single fiber tests and require much less time.

5.3 The basic differences between the procedures described in Test Method D2524 and those described in Test Method D1294 lie in the manner of clamping the bundles and the shorter gage length employed. The special clamps used in this method allow quicker and easier bundle preparation; however, for Test Method D1294 no special clamps are required. Closer agreement with single fiber tenacity is also obtained with Test Method D2524 than when using the procedure in Test Method D1294.

5.4 As the observed tenacity of fibers depends in part on the type of tensile testing machine used and the time required to break the specimen, results obtained with the different types of machines which may be used in this method will not necessarily agree. The machines specifically designed for bundle testing are CRL testers which operate at a loading rate of 1 kgf/s and therefore reach the breaking force at variable times in the order of 5 s. CRE and CRT type machines would be expected to produce somewhat different results not only because of the inherent difference in operation but because CRE and CRT type machines are to be operated at a rate to achieve the breaking load in 20 s.