ASTM D4031-07(2012)

The values obtained by this test method should not be used to predict similar properties in fabricated structures except in narrow well-defined comparisons, such as 16.7 tex (150-denier) polyester from the same feed yarn merge and textured on the same machine type. Attempts to relate yarn performance to fabric performance might result in poor correlations unless other factors affecting bulk such as yarn shrinkage and fabric finishing are eliminated.

Elapsed time between processing and testing has a marked effect on the results of this test especially during the first 72 h. Therefore, specimens should only be compared if tested after the same elapsed time. This effect is caused by stress decay which is known to be minimal beyond the seventh day and after which time the sample remains relatively stable. Comparisons are preferably made after the seventh day.

In the case of yarns having a linear density near the upper limit of the skein size directed in Table 3, an error is introduced when rounding off to full revolutions. Therefore, the calculated values for crimp contraction, etc., should only be compared with other samples of yarn of the same linear density.

Option A used with crimp development Condition 1 (dry heat oven at 120°C (248°F)) and light loads of 0.04 mN/tex (0.5 mgf/den) and 0.44 mN/tex (5.0 mgf/den) are recommended for textured polyester yarns. All crimp parameters may be calculated.

Option B may also be used with crimp development Condition 1 (dry heat) for textured polyester yarns. Crimp contraction may be calculated. When used to duplicate or to utilize suitable mechanical yarn handling devices, alternate skein size and weights may be used as described in 6.5.2 and 9.3.2.

Option C used with crimp development Condition 2 (water bath at 82°C (180°F)) and a light load of 0.13 mN/tex (1.5 mgf/den) is recommended for textured nylon yarns. For textured polyester yarns, Condition 3 (water bath at 97°C (206°F)) is recommended. Only bulk shrinkage is calculated.

This test method for the measurement of bulk properties is not recommended for acceptance testing of commercial shipments because of lack of precision data.

If there are differences or 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, test samples that are as homogeneous as possible, drawn from the material from which the disparate test results were obtained, and randomly assigned in equal numbers to each laboratory for testing. The test results from the two laboratories should be compared using a statistical test for unpaired data, at a probability level chosen prior to the testing series. If a 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.

TABLE 3 Total Size (Linear Density) of Skein

^A See Eq 2, and Note 1.

^B 100 Revolutions, linear density of skein varies.

1.1 This test method covers the measurement of the change in length of a tensioned skein of textured yarn due to change in crimp characteristics brought about by exposure to wet or dry heat. The change in length, depending on procedure, is a measure of skein shrinkage, crimp contraction, bulk shrinkage, or crimp recovery.

1.2 This test method applies to crimped, continuous multifilament yarns ranging from 1.7 to 88.9 tex (15 to 800 denier).

1.3 Three conditions are provided for crimp development mediums, and loading routines are provided to be used on the yarn skeins to allow determination of yarn bulk by several different procedures.

1.4 The values stated in either SI units or inch-pound units are to be regarded as standard. Within the text, the inch-pound units are shown in parentheses. The values stated in each system are not exact equivalent; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.

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.