ASTM D6720-07(2012)
(Test Method)Standard Test Method for Evaluation of Recoverable Stretch of Stretch Yarns (Skein Method)
Standard Test Method for Evaluation of Recoverable Stretch of Stretch Yarns (Skein Method)
SIGNIFICANCE AND USE
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.
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.
SCOPE
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.
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.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D6720 − 07 (Reapproved 2012)
Standard Test Method for
Evaluation of Recoverable Stretch of Stretch Yarns (Skein
Method)
This standard is issued under the fixed designation D6720; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2 For all other terms are related to textiles, refer to
Terminology D123.
1.1 This test method covers the determination of the recov-
erable stretch of commercial textured yarns, covered elasto-
4. Summary of Test Method
meric yarns and other stretch yarns using skeins. This test
method is particularly valuable for yarns that develop addi-
4.1 A skein of yarn is prepared by winding a prescribed
tional crimp upon exposure to hot, wet conditions. The
number of turns on a reel in order to obtain a 5000 g skein.The
recoverable stretch is a relative measure of the recovery power
skein is immersed in boiling water for 15 min and air dried to
the yarn can be expected to provide in a finished fabric.
allow the yarn skein to fully develop its stretch (crimp)
potential. The skein is exercised under a specified tension and
1.2 This test method is applicable to continuous filament
its extended length is recorded.Alessor tension is then applied
yarns and is suitable for yarns that develop additional stretch
to the skein and its recovery length is recorded. The recover-
potential upon exposure to heat.
able stretch is calculated from the difference between the
1.3 This method is applicable to yarns 500 denier or finer.
recorded length measurements and expressed as a percentage
1.4 The values stated in SI units are to be regarded as
of the recovery length.
standard. The values given in parentheses are provided for
information only.
5. Significance and Use
1.5 This standard does not purport to address all of the
5.1 This test method is considered satisfactory for accep-
safety concerns, if any, associated with its use. It is the
tance testing of commercial shipments because current esti-
responsibility of the user of this standard to establish appro-
mates of between-laboratory precision are acceptable and the
priate safety and health practices and determine the applica-
method is used extensively in the trade for acceptance testing.
bility of regulatory limitations prior to use.
5.1.1 If there are differences of practical significance be-
tween reported test results for two laboratories (or more),
2. Referenced Documents
comparative tests should be performed to determine if there is
2.1 ASTM Standards:
a statistical bias between them, using competent statistical
D123 Terminology Relating to Textiles
assistance. As a minimum, use samples for such comparative
D1776 Practice for Conditioning and Testing Textiles
teststhatareashomogeneousaspossible,drawnfromthesame
D4849 Terminology Related to Yarns and Fibers
lot of material as the samples that resulted in disparate results
during initial testing, and randomly assigned in equal numbers
3. Terminology
to each laboratory. The test results from the laboratories
3.1 For all terminology relating to D13.58, Yarns and involved should be compared using a statistical test for
Fibers, refer to Terminology D4849.
unpaired data, at a probability level chosen prior to the testing
3.1.1 The following terms are relevant to this standard: series. If bias is found, either its cause must be found and
elastomeric yarn, recoverable stretch, stretch yarn.
corrected, or future test results for that material must be
adjusted in consideration of the known bias.
1 5.2 This test differs from other crimp contraction test
This test method is under the jurisdiction ofASTM Committee D13 on Textiles
and is the direct responsibility of Subcommittee D13.58 on Yarns and Fibers. methods in that it measures the recoverable stretch during the
Current edition approved July 1, 2012. Published August 2012. Originally
unload cycle of the yarn.
approved in 2001. Last previous edition approved in 2007 as D6720 – 07. DOI:
10.1520/D6720-07R12.
6. Interferences
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
6.1 Care should be take to ensure that the skein is not lifted
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. past the point where it is supported by the yarn. If the 30 g
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6720 − 07 (2012)
weight is lifted beyond this point, a false reading will result 11. Procedure
since the yarn will be on the next cycle load extension force.
11.1 Immerse the test specimen skeins in boiling water 100°
6 1°C (212° 6 2°F) for 15 min to allow development of crimp
7. Apparatus
potential.
7.1 Reel—Ahandormotordrivenreelhavingaperimeterof
11.2 Air dry the skeins on the rack and conditioned as
1.37 m (54 in.).
directed in 9.2.
7.2 Water Bath Tank, filled with water, minimum
11.3 After drying, hang each skein on the meter stick hooks.
dimensions, 50 l capable of maintaining 100° 6 1°C (212° 6
2°F), for boiling off skeins.
11.4 Gently, apply both the 30 g and 1000 g tension weights
to the bottom of the skein.
7.3 Rack, having parallel pegs or bars placed a sufficient
distance apart to hold the skeins extended to nearly their full
11.5 After about 10 s, allow the skein to relax by manually
length without stretching, kinking or entangling the yarns.
supporting the weights by hand, so that it becomes slack.
7.4 Measuring Scales, consisting of one meter stick or other
11.6 After 10 s, allow the skein to gently extend downward
scale for each peg position on the rack, having measuring
under the 1030 g weight.
intervals of 1 mm (0.05 in.), mounted vertically with a hook at
11.7 After about 10 s, allow the skein to relax by manually
the top aligned with the scales 0 position.
supporting the weights by hand, so that it becomes slack.
7.5 Clock or Stopwatch, with second intervals.
11.8 After 10 s, reapply the force by letting the skein gently
7.6 Tension Weights—A30 g weight and either a 1000 g or
extend under the weight of the 1030 g force.
2 - 500 g weights, having tolerances of 1 %. Metal tongs, to
11.9 After 10 s, record the extended length, L , to the
remove skeins from water bath.
nearest 1 mm (0.05 in.) while under the 1030 g tension.
8. Sampling, Test Specimens, and Test Units
11.10 Place two fingers into the bottom of the skein loop
8.1 LotSample—Asalotsampleforacceptancetesting,take
just above the 30 g weight to prevent snap back while holding
a random number of
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