ASTM D6720-07(2018)

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.
Designation: D6720 − 07 (Reapproved 2018)
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. Terminology
1.1 This test method covers the determination of the recov- 3.1 For all terminology relating to D13.58, Yarns and
erable stretch of commercial textured yarns, covered elasto- Fibers, refer to Terminology D4849.
meric yarns and other stretch yarns using skeins. This test 3.1.1 The following terms are relevant to this standard:
method is particularly valuable for yarns that develop addi- elastomeric yarn, recoverable stretch, stretch yarn.
tional crimp upon exposure to hot, wet conditions. The
3.2 For all other terms are related to textiles, refer to
recoverable stretch is a relative measure of the recovery power
Terminology D123.
the yarn can be expected to provide in a finished fabric.
4. Summary of Test Method
1.2 This test method is applicable to continuous filament
yarns and is suitable for yarns that develop additional stretch 4.1 A skein of yarn is prepared by winding a prescribed
number of turns on a reel in order to obtain a 5000 g skein.The
potential upon exposure to heat.
skein is immersed in boiling water for 15 min and air dried to
1.3 This method is applicable to yarns 500 denier or finer.
allow the yarn skein to fully develop its stretch (crimp)
1.4 The values stated in SI units are to be regarded as
potential. The skein is exercised under a specified tension and
standard. The values given in parentheses are provided for
its extended length is recorded.Alessor tension is then applied
information only.
to the skein and its recovery length is recorded. The recover-
1.5 This standard does not purport to address all of the able stretch is calculated from the difference between the
recorded length measurements and expressed as a percentage
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- of the recovery length.
priate safety, health, and environmental practices and deter-
5. Significance and Use
mine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accor- 5.1 This test method is considered satisfactory for accep-
tance testing of commercial shipments because current esti-
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the mates of between-laboratory precision are acceptable and the
method is used extensively in the trade for acceptance testing.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical 5.1.1 If there are differences of practical significance be-
tween reported test results for two laboratories (or more),
Barriers to Trade (TBT) Committee.
comparative tests should be performed to determine if there is
2. Referenced Documents
a statistical bias between them, using competent statistical
assistance. As a minimum, use samples for such comparative
2.1 ASTM Standards:
teststhatareashomogeneousaspossible,drawnfromthesame
D123 Terminology Relating to Textiles
lot of material as the samples that resulted in disparate results
D1776 Practice for Conditioning and Testing Textiles
during initial testing, and randomly assigned in equal numbers
D4849 Terminology Related to Yarns and Fibers
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
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.
series. If bias is found, either its cause must be found and
Current edition approved July 1, 2018. Published August 2018. Originally
corrected, or future test results for that material must be
approved in 2001. Last previous edition approved in 2012 as D6720 – 07(2012).
adjusted in consideration of the known bias.
DOI: 10.1520/D6720-07R18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.2 This test differs from other crimp contraction test
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
methods in that it measures the recoverable stretch during the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. unload cycle of the yarn.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6720 − 07 (2018)
6. Interferences 10.2 Ensure that water bath temperature measuring devices
are within calibration.
6.1 Care should be take to ensure that the skein is not lifted
past the point where it is supported by the yarn. If the 30 g 10.3 Bring bath water to 100° 6 1°C (212° 6 2°F).
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°
7. Apparatus
6 1°C (212° 6 2°F) for 15 min to allow development of crimp
potential.
7.1 Reel—Ahand or motor driven reel having a perimeter of
1.37 m (54 in.).
11.2 Air dry the skeins on the rack and conditioned as
directed in 9.2.
7.2 Water Bath Tank, filled with water, minimum
dimensions, 50 l capable of maintaining 100° 6 1°C (212° 6
11.3 After drying, hang each skein on the meter stick hooks.
2°F), for boiling off skeins.
11.4 Gently, apply both the 30 g and 1000 g tension weights
7.3 Rack, having parallel pegs or bars placed a sufficient
to the bottom of the skein.
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 MeasuringScales, 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 exten
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