ASTM D1425/D1425M-14(2020)

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: D1425/D1425M − 14 (Reapproved 2020)
Standard Test Method for
Evenness of Textile Strands Using Capacitance Testing
Equipment
This standard is issued under the fixed designation D1425/D1425M; 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 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the indirect measurement of
D123 Terminology Relating to Textiles
evenness (mass variation) of non-conductive textile strands,
D1776 Practice for Conditioning and Testing Textiles
including top, comber lap, sliver, roving, and yarn produced
D2258 Practice for Sampling Yarn for Testing
from staple fibers and continuous filament yarns, by means of
D4849 Terminology Related to Yarns and Fibers
capacitance testing equipment.
E177 Practice for Use of the Terms Precision and Bias in
1.2 Strands made from fiber blends can be tested using this
ASTM Test Methods
testmethodonlyifthedifferentfibersareuniformlydistributed
E691 Practice for Conducting an Interlaboratory Study to
throughout the strand.
Determine the Precision of a Test Method
1.3 The test method provides numeric values for the mea-
3. Terminology
surement and evaluation of short-, mid-, and long-term mass
3.1 Definitions:
variations of the tested strand in terms of frequently occurring
3.1.1 The following terms are relevant to this standard:
faults classified as thin places, thick places, and neps and
electric constant; evenness; imperfections; length between, L ;
b
graphical representations of evenness values in the form of
length capacitance zone, L ; mass variation; mean deviation of
c
diagram charts, spectrograms, length variation curves, and
evenness, U%; sample length L ; strand; strand irregularity;
s
histograms.
and total imperfections.
1.4 The values stated in either SI units or inch-pound units
3.1.2 For definitions of other textile terms used in this test
are to be regarded separately as standard. The values stated in
method, refer to Terminology D123 and Terminology D4849.
each system may not be exact equivalents; therefore, each
4. Basic Principles of Test Method
system shall be used independently of the other. Combining
values from the two systems may result in non-conformance
4.1 Properties of strand irregularity measured along its
with the standard.
length are measured in terms of mass variation.
1.5 This standard does not purport to address all of the
4.2 The direct method of evenness testing utilizes the
safety concerns, if any, associated with its use. It is the
techniqueofcuttingandweighingstrandsegmentsoflength L
b
responsibility of the user of this standard to establish appro-
and is the reference method of determining evenness (mass
priate safety, health, and environmental practices and deter-
variation). Utilization of the capacitance measurement tech-
mine the applicability of regulatory limitations prior to use.
nique is an indirect testing method.The accuracy of an indirect
method of testing can be judged by a comparison of evenness
1.6 This international standard was developed in accor-
values between it and the direct method (cutting and weigh-
dance with internationally recognized principles on standard-
ing).
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
4.3 In capacitance testing, a high frequency electric field is
mendations issued by the World Trade Organization Technical
generated in the space between a pair of capacitor plates
Barriers to Trade (TBT) Committee.
(measuring slots). If the mass of a strand moving between the
plates changes, the electrical field between the plates changes
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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2020. Published February 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1956. Last previous edition approved in 2014 as D1425/D1425M-14. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D1425_D1425M-14R20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1425/D1425M − 14 (2020)
accordingly, and results in electrical signal output variation L ; (3) the sample length, Ls; (4) instrument test speed, (5)
c
proportional to the mass variation of the strand. laboratory temperature and humidity conditions (see 10.1); and
(6) test specimen preparation, and (7) test specimen variation.
4.4 Evenness is always expressed as variation between
When different models of an instrument are used, and one or
successive lengths L and over a total length Ls. When the L
c
more of the seven parameters are not identical, test results may
evenness is measured, it corresponds to the length capacitance
differ.
zone width, i.e., 8 mm [0.3 in.] for yarns, 12 mm [0.5 in.] for
rovings and fine slivers, and 20 mm [0.8 in.] for slivers that are 6.6 If there are any differences of practical significance
referred to as short-term evenness. Longer-term evenness may between reported test results for two (or more) laboratories,
also be evaluated by electronically increasing the L . comparative tests should be performed using an agreed upon
c
number of samples that are homogeneous and randomly
5. Summary of Test Method
assigned. Competent statistical assistance should be used to
5.1 A textile strand is passed through a length capacitance determine if there is a statistically significant difference be-
tween the laboratories. If a bias is found, either its cause must
zone of an evenness tester at a constant speed. The mass
variation of successive L interval lengths is measured and be found and corrected, or future testing for that material must
c
be adjusted in consideration of the statistically significant
from which other values of evenness are derived: coefficient of
differences found.
variation, short-, mid- and long-term variations, and imperfec-
tions.
7. Apparatus
6. Significance and Use
7.1 Capacitance-TypeEvennessTestingInstruments—Atex-
6.1 This test method for the determination of evenness of
tile strand evenness tester that utilizes the electronic capaci-
textile strands is used extensively for acceptance testing of
tance measuring principle.
commercial shipments of filament or spun staple yarn, comber
7.1.1 Differences between older and newer capacitance
laps, roving, sliver, or tops.
testers for calibration, recording devices, test settings, and data
output can be found in the manufacturer’s instruction manual
6.2 Values of strand evenness are also used in quality
for specific models.
control, process optimization, and together with yarn strength
measurements, as the first appraisal of a strand’s quality.Alow
7.2 Package holders, guides, tension devices, unwinding,
evenness value is, in general, preferred. Higher evenness
and take-up mechanisms——Devices and attachments to even-
values generally indicate poor yarn manufacturing practices,
ness testing instruments that aid in the uniform delivery of the
lower yarn strength, and poorer fabric appearance. Experience
strand at specified speed, without undue acceleration or
has shown that the relationship of evenness to the prediction of
deceleration, at a reasonably constant tension. These devices
yarn performance and to fabric appearance is not a simple one.
are especially critical for loose textile strands such as sliver,
An evenness value must, therefore, be used cautiously and be
roving, and comber laps
supplemented by additional evenness information, such as
7.3 Recording device—Printer or computer-generated files
mid-term and long-term mass variations, thin, thick, and nep
from which numeric and graphic test data can be produced.
imperfection counts, diagram chart spectrogram chart, length
7.4 Twist insertion device—A mechanism that inserts false
variation curve, and histogram analyses.
twist into continuous filament yarns. This mechanism is used
6.3 Continuous filament yarns should be tested for mass
only on evenness testers that are designed to test continuous
variation on evenness testers that are specifically designed to
filament yarns.
test this yarn type; failure to do so will result in inaccurate test
results. Further, low-twist, continuous filament yarns tend to
8. Sampling
flatten to a ribbon configuration while passing through the
8.1 Unless otherwise agreed upon, as when specified in an
sensor of a capacitance instrument. This flattening effect will
applicable material specification, take a lot sample and labo-
cause false mass variation measurements by the capacitive
ratory sample as directed in Practice D2258.
sensor(commonlyreferredtoasshapeeffect).Evennesstesters
that are specifically designed to test continuous filament yarns
8.2 Typical spun yarn sample lots are ten or twenty
insertafalsetwisttotheyarnstrandduringtestingtoovercome
packages, unless otherwise agreed upon.
the flattening effect and thus ensure accurate mass variation
measurements. 9. Number of Specimens
6.4 Strands made from fiber blends should be tested only if 9.1 Conduct a test on each yarn package or bobbin in the
the different fibers are uniformly distributed throughout the sample lot. Refer to 11.1, Table 1 for the recommended test
strand. Non-uniform blending may cause a higher reading of length. If required, multiple tests on successive test lengths can
massvariationthanthetruevalueifthecomponentfibersdiffer be performed on each package or bobbin.
in dielectric constant.
9.2 Conduct a test on each sample of sliver, roving, comber
6.5 Evenness values obtained on different instruments will lap, top or the number of test recommended by the equipment
be comparable for strands from the same sample provided the manufacturer. Refer to 11.1, Table 1 for the recommended test
following parameters are the same in all cases: (1) the measure length. If required, multiple tests on successive test lengths can
of evenness used (CV% or U%); (2) the capacitive length zone be performed on each sample.
D1425/D1425M − 14 (2020)
TABLE 1 Recommended Strand Speeds and Evaluating Times
Material Strand Speed Evaluating Time
Top or sliver 4 m/min [4 yd/min] 5 or 10 min
Sliver or roving 8 m/min [8 yd/min] 5 or 10 min
Sliver or roving 25 m/min [25 yd/min] 5 or 10 min
Sliver 50, 100 m/min [50, 1
...