ASTM D2731-07(2012)
(Test Method)Standard Test Method for Elastic Properties of Elastomeric Yarns (CRE Type Tensile Testing Machines)
Standard Test Method for Elastic Properties of Elastomeric Yarns (CRE Type Tensile Testing Machines)
SIGNIFICANCE AND USE
This test method is considered satisfactory for acceptance testing of commercial shipments since 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.
Force at Specified Elongation (FASE) is a measure of the tensile force required to extend a textile material within specified limits. This characteristic of elastomeric yarn indicates the resistance that will have to be overcome by the wearer while putting on a garment made of the material and is also an indication of the garment's resistance to deformation caused by normal body movements during wear. The elongations used for these measurements are typically 100 %, 200 % and 300 %.
Permanent Deformation (set) is a measure of the increase in length of an elastomeric yarn resulting from cyclic stretching and relaxation. The characteristic is a visible indication of the realignment of intermolecular bonds within the elastic material. As with stress decay, the amount of set increases with yarn extension; however, for any particular extension, little or no additional set takes place after five cycles of exercising. ...
SCOPE
1.1 This test method covers the determination of elastic properties of “as produced” elastomeric yarns made from rubber, spandex or other elastomers. Elastic properties include force at specified elongations, permanent deformation and stress decay. Other hysteresis related properties can be calculated.
Note 1—For a method designed specifically for testing rubber threads, refer to Test Method D2433.
1.2 This test method is not applicable to covered, wrapped, or core-spun yarns or yarns spun from elastomeric staple.
1.3 This test method is applicable to elastomeric yarns having a range of 40 to 3200 dtex (36 to 2900 denier).
1.4 The values stated in either SI units or U.S. Customary units are to be regarded separately as standard. Within the text, the U.S. Customary units are in parentheses. The values stated in each system are not exact equivalents; therefore, each system shall be used independently of the other.
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.
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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: D2731 − 07(Reapproved 2012)
Standard Test Method for
Elastic Properties of Elastomeric Yarns (CRE Type Tensile
Testing Machines)
This standard is issued under the fixed designation D2731; 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 D2433 Test Methods for Rubber Thread (Withdrawn 2012)
D2591 Test Method for Linear Density of ElastomericYarns
1.1 This test method covers the determination of elastic
(Short Length Specimens)
properties of “as produced” elastomeric yarns made from
D2653 Test Method for Tensile Properties of Elastomeric
rubber, spandex or other elastomers. Elastic properties include
Yarns (CRE Type Tensile Testing Machines)
force at specified elongations, permanent deformation and
D4848 Terminology Related to Force, Deformation and
stress decay. Other hysteresis related properties can be calcu-
Related Properties of Textiles
lated.
D4849 Terminology Related to Yarns and Fibers
NOTE 1—For a method designed specifically for testing rubber threads,
D6717 Test Method for Linear Density of ElastomericYarns
refer to Test Method D2433.
(Skein Specimens)
1.2 This test method is not applicable to covered, wrapped,
3. Terminology
or core-spun yarns or yarns spun from elastomeric staple.
3.1 For all terminology relating to D13.58, Yarns and
1.3 This test method is applicable to elastomeric yarns
Fibers, refer to Terminology D4849.
having a range of 40 to 3200 dtex (36 to 2900 denier).
3.1.1 The following terms are relevant to this standard:
1.4 The values stated in either SI units or U.S. Customary
deformation, elastomeric yarn, elongation, force at specified
units are to be regarded separately as standard. Within the text,
elongation,lineardensity,permanentdeformation,stress,stress
the U.S. Customary units are in parentheses. The values stated
decay.
in each system are not exact equivalents; therefore, each
3.2 For definitions of other terms related to force and
system shall be used independently of the other.
deformation, refer to Terminology D4848. For all other terms
1.5 This standard does not purport to address all of the
related to textiles, refer to Terminology D123.
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
4.1 Aspecimen, mounted in a CRE-type tensile machine, is
bility of regulatory limitations prior to use.
initially subjected to a series of five loading/unloading cycles
in which the specimen is extended and relaxed between zero
2. Referenced Documents
and 75 % of the elongation at first filament break (FFB).
During the fifth cycle, the specimen is held at the maximum
2.1 ASTM Standards:
extension point for 30 s, then unloaded to allow a return to its
D76 Specification for Tensile Testing Machines for Textiles
original gage length position. The specimen is then subjected
D123 Terminology Relating to Textiles
to a sixth load/unload cycle.
D1776 Practice for Conditioning and Testing Textiles
D2258 Practice for Sampling Yarn for Testing
4.2 Force at specified elongations are calculated from the
force-elongation curve for the first and fifth loadings and for
thefifthunloading.Stressdecayiscalculatedonthefifthcycle.
Extension at a specified force is determined on the sixth
loading and is used to calculate the permanent deformation.
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.
5. Significance and Use
Current edition approved July 1, 2012. Published August 2012. Originally
approved in 1968. Discontinued 1979 and reinstated as D2731 – 01. Last previous
5.1 This test method is considered satisfactory for accep-
edition approved in 2007 as D2731–07. DOI: 10.1520/D2731-07R12.
tance testing of commercial shipments since current estimates
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
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2731 − 07 (2012)
of between-laboratory precision are acceptable and the method ofcycling,anddesignedforoperationatapullingspeedof500
is used extensively in the trade for acceptance testing. mm/min (20 in./min).
5.1.1 If there are differences of practical significance be-
6.3 Clamping Assembly, pneumatically operated, with jaws
tween reported test results for two laboratories (or more),
as described in Test Method D2653.
comparative tests should be performed to determine if there is
6.4 Computer or Microprocessor,interfaced,withautomatic
a statistical bias between them, using competent statistical
data gathering system, optional.
assistance. As a minimum, use samples for such comparative
teststhatareashomogeneousaspossible,drawnfromthesame
6.5 Tensioning Weights, with various masses from 10 mg to
lot of material as the samples that resulted in disparate results
3 g to pretension the specimen to 30 to 50 mN/tex (0.3 to 0.5
during initial testing, and randomly assigned in equal numbers
mgf/d) before testing.
to each laboratory. The test results from the laboratories
6.6 Air Supply, capable of providing 415 kPa (60 psi) to the
involved should be compared using a statistical test for
pneumatic clamps.
unpaired data, at a probability level chosen prior to the testing
series. If bias is found, either its cause must be found and
7. Sampling, Test Specimens, and Test Units
corrected, or future test results for that material must be
adjusted in consideration of the known bias. 7.1 Lot Sample—Asalotsampleforacceptancetesting,take
a random number of shipping units directed in an applicable
5.2 Force at Specified Elongation (FASE) is a measure of
material specification or other agreement between the pur-
the tensile force required to extend a textile material within
chaser and the supplier, such as an agreement to use Practice
specified limits. This characteristic of elastomeric yarn indi-
D2258. Consider shipping cases or other shipping units to be
catestheresistancethatwillhavetobeovercomebythewearer
the primary sampling units.
while putting on a garment made of the material and is also an
indicationofthegarment’sresistancetodeformationcausedby
NOTE 2—An adequate specification or other agreement between the
purchaser and the supplier requires taking into account the variability
normalbodymovementsduringwear.Theelongationsusedfor
between shipping units, between packages or ends within a shipping unit,
these measurements are typically 100 %, 200 % and 300 %.
and between specimens from a single package to provide a sampling with
5.3 Permanent Deformation (set) is a measure of the in- a meaningful producer’s risk, consumer’s risk, acceptable quality level
and limiting quality level.
crease in length of an elastomeric yarn resulting from cyclic
stretching and relaxation. The characteristic is a visible indi-
7.2 Laboratory Sample—As a laboratory sample for accep-
cation of the realignment of intermolecular bonds within the
tance testing, take at random from each shipping unit in the lot
elastic material. As with stress decay, the amount of set
sample the number of packages directed in an applicable
increases with yarn extension; however, for any particular
material specification or other agreement between the pur-
extension,littleornoadditionalsettakesplaceafterfivecycles
chaser and the supplier, such as an agreement to use Practice
of exercising. Generally, the characteristic set of the yarn is
D2258. Preferably, take the same number of packages from
developed during fabric preparation and the fabric itself shows
each of the shipping units selected. If differing numbers of
a negligible amount of set.
packages are to be taken from the shipping units, determine at
random which shipping units are to have each number of
5.4 Stress decay increases with yarn extension, but at any
packages for testing.
specified extension the stress decay takes place in the first 30
s with insignificant decay after 5 min. This characteristic is
7.3 Test Specimens—From each package or end in the
caused by the gradual realignment of intermolecular bonds
laboratory sample, take six specimens as directed in 7.3.1.
within the elastic material, and helps to explain the changes in
7.3.1 Remove the outer layer of yarn from the package.
yarn properties that accompany cyclic stretching and relaxing.
Avoid any damaged areas in selecting segments for testing.
The realignment of the bonds is a reversible effect. Following
Carefullyunwindyarnfromthepackagewithaslowastension
complete relaxation of the yarn, the molecules tend to assume
as possible to avoid stretching.As test specimens, cut approxi-
their original configuration with just about complete elimina-
mately 125 mm (5 in.) long segments of yarn from each
tion of the previously observed strain.
package, taking them at intervals of at least1m(1 yd). Three
ofthesixspecimensareusedassparetoallowforunacceptable
5.5 This test method was developed using elastomeric yarns
breaks, such as caused by slippage or breaking in the clamps.
in the “as-produced” condition, but may be used for treated
elastomeric yarns provided the treatment is specified. The
7.4 Determine the tex (denier) of the yarn for each labora-
method does not cover the removal of finish for the determi-
tory sample using Test Method D2591 or Test Method D6717.
nation of elastic properties of “finish-free” elastomeric yarns.
7.5 Determine the elongation at first filament bread (FFB)
for each laboratory sample as directed in Test Method D2653.
6. Apparatus
6.1 Specimen Boards, with short pile or plush surfaces of
8. Preparation of Apparatus and Calibration
black or contrasting color, for storing specimens during con-
8.1 Prepare and verify the calibration of the tensile testing
ditioning.
machine as directed in the manufacturer’s instructions.
6.2 Tensile Testing Machine, CRE-type, conforming to
Specification D76 with respect to force indication, working 8.2 Set up and adjust the CRE-type tensile testing machine
range,capacityandverificationofrecordedelongation,capable as follows:
D2731 − 07 (2012)
NOTE 5—If using a chart recorder, only the first loading cycle and
8.2.1 Examine the acrylic clamp jaw face for wear and
complete fifth cycle need be recorded on the chart.
replace as needed. Position the jaw faces horizontally in the
clamps.
10.7 On the fifth cycle, stop the crosshead at the maximum
8.2.2 Setthedistancebetweenthejawfaces(gagelength)to
extension limit and hold for 30 s. At the end of holding at the
50 61mm(2 6 0.05 in.).
maximum extension limit, return the crosshead to gage length.
NOTE 3—A convenient technique for checking the gage length is to 10.8 Immediately,startthecrossheadandrecordtheloading
place a piece of carbon paper and white paper in the clamps and close the
portion of a sixth cycle.
clamps. The distance between the marks made on the white paper by the
carbon paper represents the set gage length. 10.9 Return the crosshead to the zero position, remove the
spectrum and continue testing until all specimens have been
8.2.3 Use a force measuring system such that the cycling
tested for each laboratory sampling unit and for the lot.
force will be between 30 and 80 % of full scale capacity.
8.2.4 Set the Cycling Limits as follows:
11. Calculation or Interpretation of Results
8.2.4.1 Set Minimum Extension to nominal gage length
(zero extension).
11.1 Force at Specified Elongation (FASE)—Determine the
8.2.4.2 Set Maximum Extension equivalent to 75 % of the
FASE as follows:
elongation at first filament break of the elastomeric yarn (see
11.1.1 From the tensile hysteresis chart for each specimen,
10.2) or 300 % of gauge length.
read and record the force at 100, 200 and 300 % elongation on
8.2.5 Setthecrossheadspeedto500mm/min(20in./min)or
the first loading cycle, the force at 300 % elongation on the
1000 % extension per min.
fifth loading cycle, prior to holding for 30 s, and the force at
8.2.6 Set the extension measuring system as follows:
100 and 200 % elongation of the fifth unloading cycle to the
8.2.6.1 When using a chart recorder, set the chart speed to
nearest cN (0.1 gf).
500 mm/min (20 in./min).
11.1.2 Calculate the average FASE for each of the elonga-
8.2.6.2 When using an interfaced computer or
tions and applicable cycles determined in 11.1.1 for each
microprocessor, set parameters to obtain selected properties
laboratory sampling unit and for the lot to the nearest cN (0.1
using supplier’s directions and Specification D76.
gf).
8.2.7 Set the air pressure for pneumatic clamps to 415 kPa
11.2 Stress Decay—Determine the percent stress decay as
(60 psi). At this pressure, the clamping force is approximately
follows:
450 N (100 lb).
11.2.1 From the chart and on the fifth loading cycle, read
9. Conditioning and record the force at maximum extension and the force after
holding at maximum extension for 30-s for each specimen.
9.1 No preconditioning is required for currently produced
11.2.2 Calculate the average percent stress decay for each
rubber yarns and other elastomeric yarns.
specimen to the nearest 0.1 %, using Eq 1
9.2 Condition the specimens relaxed on specimen boards in
5 5 5
D 5 100 F 2 F /F (1)
~ !
L U L
the standard atmosphere for testing textiles as directed in
Practice D1776, which is 21 6 1°C (70 6 2°F) and 65 62%
where:
relative humidity for a minimum of 4 h.
D = stress decay, %,
F = loadingforceatmaximumextensiononfifthcycle,cN
L
10. Procedure
(gf), and
F = unloading force after 30-s hold on fifth cycle (start of
10.1 Test the relaxed specimens in the standard atmosphere
U
unload cycle), cN (gf).
for testing textiles.
NOTE 6—Stress in yarns is expressed as force per unit area or force per
NOTE4—Theforcemeasuringsystemshouldbezeroedpriortorunning
linear density. However, the units of force are used in Eq 1 because the
any specimens and periodically during the course of the test, particularly
areaorlineardensityinunitsofstresseffectivelycanceloneanotherinthe
if drift is observed in the zero value of the force measuring system.
equation.
10.2 Select the appropriate pretensioning weight based on
11.2.3 Calculate the average percent stress decay for each
the
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