1、Designation: D1425/D1425M 091D1425/D1425M 14Standard Test Method forUnevennessEvenness of Textile Strands Using CapacitanceTesting Equipment1This standard is issued under the fixed designation D1425/D1425M; the number immediately following the designation indicates theyear of original adoption or, i
2、n the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1 NOTEFootnotes A and B were added to Table 1 in April 2012.1. Scope1.1 This test method cover
3、s the indirect measurement of evenness (mass variation) of non-conductive textile strands, includingtop, comber lap, sliver, roving, and yarn produced from staple fibers and continuous filament yarns, by means of capacitance testingequipment.1.2 Strands made from fiber blends can be tested using thi
4、s test method only if the different fibers are uniformly distributedthroughout the strand.1.3 The test method provides numeric values for the measurement and evaluation of short-, mid-, and long-term mass variationsof the tested strand in terms of frequently occurring faults classified as thin place
5、s, thick places, and neps and graphicalrepresentations of evenness values in the form of diagram charts, spectrograms, length variation curves, and histograms.1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in eachsystem may n
6、ot be exact equivalents; therefore, each system shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsi
7、bilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD1776 Practice for Conditioning and Testing TextilesD2258 Prac
8、tice for Sampling Yarn for TestingD4849 Terminology Related to Yarns and FibersE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 electric const
9、ant, nin textile capacitance testing, the change in the electrical field as measured by the sensors(capacitors) of an evenness instrument when a non-conductive textile strand travels between capacitor plates.3.1.1.1 DiscussionThe dielectric change is measured as the ratio of the amount of stored ene
10、rgy between the capacitors without a strand and duringthe movement of a strand through the sensor zone and is in direct proportion to the mass variation that is output to a diagram chart.1 This test method is under the jurisdiction of ASTM Committee D13 on Textiles and is the direct responsibility o
11、f Subcommittee D13.58 on Yarns and Fibers.Current edition approved July 1, 2009July 1, 2014. Published August 2009August 2014. Originally approved in 1956. Discontinued May 2005 and reinstated Last previousedition approved in 2009 as D1425/D1425M-09. DOI: 10.1520/D1425_D1425M-09-091. DOI: 10.1520/D1
12、425_D1425M-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is in
13、tended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the cur
14、rent versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 The following terms are relevant to this standard: electric constant; evenness; imperfect
15、ions; length between, Lb; lengthcapacitance zone, Lc; mass variation; mean deviation of evenness, U%; sample length Ls; strand; strand irregularity; and totalimperfections.3.1.2 evenness, CV% (or U%), n in textiles, the coefficient of mass variation derived from the standard deviation of the massvar
16、iation of a specified strand length (Ls ) over the mass variation (formerly known as unevenness).3.1.2.1 DiscussionFor strands with normal mass variation distribution, the relationship between CV% and U% is U% is multiplied by 1.25.Althoughboth CV% and U% are used as values of evenness, CV% is consi
17、dered more accurate CV% is gradually replacing U% as the onlycalculated measurement of evenness.3.1.3 imperfections, nin textile evenness testing, the individual number of thick places, thin places, and neps of a samplestrand length measured by a capacitive evenness tester at selected sensitivity se
18、ttings.3.1.4 length between, Lb, nin textile evenness testing, the length of strand segments weighed to determine evenness for thedirect method (cut (2) an ordered assemblage of textile fibers having a high ratio oflength to diameter and normally used as a unit, including sliver, roving, single yarn
19、s, plied yarns, cords, braids, and ropes.3.1.10 strand irregularity, nin textiles, the variation in a property along a strand.3.1.11 total imperfections, nin textile evenness testing, an evenness value that is the cumulative number thicks, thins, and nepsfrom a tested strand, strands from a sample,
20、or lot sample.3.1.2 For definitions of other textile terms used in this test method, refer to Terminology D123 and Terminology D4849.4. Basic Principles of Test Method4.1 Properties of strand irregularity measured along its length are measured in terms of mass variation.4.2 The direct method of even
21、ness testing utilizes the technique of cutting and weighing strand segments of length Lb and isthe reference method of determining evenness (mass variation). Utilization of the capacitance measurement technique is an indirecttesting method. The accuracy of an indirect method of testing can be judged
22、 by a comparison of evenness values between it andthe direct method (cutting and weighing).4.3 In capacitance testing, a high frequency electric field is generated in the space between a pair of capacitor plates (measuringslots). If the mass of a strand moving between the plates changes, the electri
23、cal field between the plates changes accordingly, andresults in electrical signal output variation proportional to the mass variation of the strand.4.4 Evenness is always expressed as variation between successive lengths L and over a total length Ls. When the Lc evennessis measured, it corresponds t
24、o the length capacitance zone width, i.e., 8 mm (0.3 in)0.3 in. for yarns, 12 mm (0.5 in)0.5 in. forrovings and fine slivers, and 20 mm (0.8 in)0.8 in. for slivers that are referred to as short-term evenness. Longer-term evennessmay also be evaluated by electronically increasing the Lc.D1425/D1425M
25、1425. Summary of Test Method5.1 A textile strand is passed through a length capacitance zone of an evenness tester at a constant speed. The mass variationof successive Lc interval lengths is measured and from which other values of evenness are derived: coefficient of variation, short-,mid- and long-
26、term variations, and imperfections.6. Significance and Use6.1 This test method for the determination of evenness of textile strands is used extensively for acceptance testing of commercialshipments of filament or spun staple yarn, comber laps, roving, sliver, or tops. 6.2 6.3 6.4 6.5 Evenness values
27、 obtained on differentinstruments will be comparable for strands from the same sample provided the following parameters are the same in all cases: (1)the measure of evenness used; (2) the capacitive length zone L (see 3.1.5 and 3.1.5.1); (3) the sample length, Ls (see 3.1.8); (4)instrument test spee
28、d, (5) laboratory temperature and humidity conditions (see 12.1 and 12.1.1); and (6) test specimen variation.When different models of an instrument are used, and one or more of the six parameters are not identical, test results may differ.6.2 Values of strand evenness are also used in quality contro
29、l, process optimization, and together with yarn strengthmeasurements, isas the first appraisal of a strands quality. A low evenness value is, in general, preferred. Higher evenness valuesgenerally indicate difficult spinning, poor yarn manufacturing practices, lower yarn strength, and poorer fabric
30、appearance.Experience has shown that the relationship of evenness to the prediction of yarn performance and to fabric appearance is not asimple one. An evenness value must, therefore, be used cautiously and be supplemented by additional evenness information, suchas mid-term and long-term mass variat
31、ions, thin, thick, and nep imperfection counts, diagram chart spectrogram chart, lengthvariation curve, and histogram analyses.6.3 Continuous filament yarns should be tested for mass variation on instruments evenness testers that are specifically designedto them.; test this yarn type; failure to do
32、so will result in inaccurate test results. Further, low-twist, continuous filament yarns tendto flatten to a ribbon configuration while passing through the condensersensor of a capacitance instrument. These specificinstruments are designed to insert false twist in the condenser This flattening effec
33、t will cause false mass variation measurementsby the capacitive sensor (commonly referred to as shape effect). Evenness testers that are specifically designed to test continuousfilament yarns insert a false twist to the yarn strand during testing to overcome the flattening effect and may result in f
34、alse variationreadings.thus ensure accurate mass variation measurements.6.4 Strands made from fiber blends should be tested only if the different fibers are uniformly distributed throughout the strand.Non-uniform blending may cause a higher reading of mass variation than the true value if the compon
35、ent fibers differ in dielectricconstant (see 3.1.1 and 3.1.1.1).constant.6.5 Evenness values obtained on different instruments will be comparable for strands from the same sample provided thefollowing parameters are the same in all cases: (1) the measure of evenness used; used (CV% or U%); (2) the c
36、apacitive lengthzone Lc (see 3.1.5 and 3.1.5.1); ; (3) the sample length, Ls (see 3.1.8); ; (4) instrument test speed, (5) laboratory temperature andhumidity conditions (see 10.112.1); and 12.1.1); and (6) test specimen preparation, and (7) test specimen variation. When differentmodels of an instrum
37、ent are used, and one or more of the sixseven parameters are not identical, test results may differ.6.6 If there are any differences of practical significance between reported test results for two (or more) laboratories, comparativetesttests should be performed using competent statistical assistance
38、 and an agreed upon number of samples that are homogeneousand randomly assigned, assigned. Competent statistical assistance should be used to determine if there is a statistically significantdifference between them. the laboratories. If a bias is found, either its cause must be found and corrected,
39、or future testing for thatmaterial must be adjusted in consideration of the statistically significant differences found.7. Apparatus7.1 Capacitance-Type UnevennessEvenness Testing InstrumentsA textile strand evenness tester that utilizes the electroniccapacitance measuring principle.7.1.1 Difference
40、s between older and newer capacitance testers for calibration, recording devices, test settings, and data outputcan be found in the manufacturers instruction manual for specific models.7.2 Package holders, guides, tension devices, unwinding, and take-up mechanismsDevices and attachments to evennesst
41、esting instruments that aid in the uniform delivery of the strand at specified speed, without undue acceleration or deceleration, ata reasonably constant tension. These devices are especially critical for loose textile strands such as sliver, roving, and comber laps7.3 Recording devicePrinter or com
42、puter-generated files from which numeric and graphic test data can be produced.7.4 Twist insertion deviceA mechanism in the condenser zone of an evenness testing instrument that inserts false twist intocontinuous filament yarnsthat inserts false twist into continuous filament yarns. This mechanism i
43、s used only on evenness testersthat are designed to test continuous filament yarns.8. Sampling8.1 Unless otherwise agreed upon, as when specified in an applicable material specification, take a lot sample and laboratorysample as directed in Practice D2258.D1425/D1425M 1438.2 Typical spun yarn sample
44、 lots are ten or twenty packages. Unless otherwise agreed upon, as when specified in an applicablematerial specification, take a lot sample and laboratory sample as directed in.packages, unless otherwise agreed upon.9. Number of Specimens9.1 Conduct a test on one strand from each yarn package or bob
45、bin in the sample lot. Refer to 11.1, Table 1 for the recommendedtest length. If required, multiple tests on successive test lengths can be performed on each package or bobbin.9.2 Test three strands from silver, roving, comber laps or tops or the recommended number of equipment manufacturer. Conduct
46、a test on each sample of sliver, roving, comber lap, top or the number of test recommended by the equipment manufacturer. Referto 11.1, Table 1 for the recommended test length. If required, multiple tests on successive test lengths can be performed on eachsample.10. Conditioning10.1 Condition strand
47、s according to Practice D1776. Preconditioning is not required unless in the case of dispute.10.2 For yarn, the time required for conditioning depends on the fiber, the size of the package and the compactness of the yarnwound on the package. Further, a shorter conditioning time may be sufficient if
48、only the outside layer of a yarn package is to betested than if the whole package is to be tested. As a general guide, condition tightly wound bobbins for 24 h and yarn packagesfor 48 h. Other strands such as sliver, roving, and laps maydo not require conditioning and can be tested as soon as they a
49、re broughtinto the laboratory.10.3 If the standard atmosphere described in Practice D1776 is not available, condition the strand in a stable atmosphere inwhich the test is to be performed until it has reached equilibrium. Record the conditions under which the test was performed.10.4 Test results may not be comparable if conditioned and tested in different atmospheres.11. Selection of Testing Parameters11.1 Measure of UnevennessEvennessRecommended evaluation test times and strand speeds are listed in Table 1.11.1.1 The selection of test speeds is importa
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