1、Designation: D1425/D1425M 091Standard Test Method forUnevenness of Textile Strands Using Capacitance TestingEquipment1This standard is issued under the fixed designation D1425/D1425M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision,
2、 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.1NOTEFootnotes A and B were added to Table 1 in April 2012.1. Scope1.1 This test method covers the indirect measureme
3、nt ofevenness (mass variation) of non-conductive textile strands,including top, comber lap, sliver, roving, and yarn producedfrom staple fibers and continuous filament yarns, by means ofcapacitance testing equipment.1.2 Strands made from fiber blends can be tested using thistest method only if the d
4、ifferent fibers are uniformly distributedthroughout the strand.1.3 The test method provides numeric values for the mea-surement and evaluation of short-, mid-, and long-term massvariations of the tested strand in terms of frequently occurringfaults classified as thin places, thick places, and neps a
5、ndgraphical representations of evenness values in the form ofdiagram charts, spectrograms, length variation curves, andhistograms.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; there
6、fore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standar
7、d to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD1776 Practice for Conditioning and Testing TextilesD2258 Practice for Sampling Yarn for Tes
8、tingD4849 Terminology Related to Yarns and Fibers3. Terminology3.1 Definitions:3.1.1 electric constant, nin textile capacitance testing, thechange in the electrical field as measured by the sensors(capacitors) of an evenness instrument when a non-conductivetextile strand travels between capacitor pl
9、ates.3.1.1.1 DiscussionThe dielectric change is measured asthe ratio of the amount of stored energy between the capacitorswithout a strand and during the movement of a strand throughthe sensor zone and is in direct proportion to the mass variationthat is output to a diagram chart.3.1.2 evenness, CV%
10、 (or U%), n in textiles, the coeffi-cient of mass variation derived from the standard deviation ofthe mass variation of a specified strand length (Ls) over themass variation (formerly known as unevenness).3.1.2.1 DiscussionFor strands with normal mass variationdistribution, the relationship between
11、CV% and U% is U% ismultiplied by 1.25. Although both CV% and U% are used asvalues of evenness, CV% is considered more accurate CV% isgradually replacing U% as the only calculated measurement ofevenness.3.1.3 imperfections, nin textile evenness testing, the indi-vidual number of thick places, thin pl
12、aces, and neps of asample strand length measured by a capacitive evenness testerat selected sensitivity settings.3.1.4 length between, Lb, nin textile evenness testing, thelength of strand segments weighed to determine evenness forthe direct method (cut (2) an ordered assemblage of textile fibers ha
13、ving a high ratioof length to diameter and normally used as a unit, includingsliver, roving, single yarns, plied yarns, cords, braids, andropes.3.1.10 strand irregularity, nin textiles, the variation in aproperty along a strand.3.1.11 total imperfections, nin textile evenness testing,anevenness valu
14、e that is the cumulative number thicks, thins, andneps from a tested strand, strands from a sample, or lot sample.3.1.12 For definitions of other textile terms used in this testmethod, refer to Terminology D123 and Terminology D4849.4. Basic Principles of Test Method4.1 Properties of strand irregula
15、rity measured along itslength are measured in terms of mass variation.4.2 The direct method of evenness testing utilizes thetechnique of cutting and weighing strand segments of length Lband is the reference method of determining evenness (massvariation). Utilization of the capacitance measurement te
16、ch-nique is an indirect testing method. The accuracy of an indirectmethod of testing can be judged by a comparison of evennessvalues between it and the direct method (cutting and weigh-ing).4.3 In capacitance testing, a high frequency electric field isgenerated in the space between a pair of capacit
17、or plates(measuring slots). If the mass of a strand moving between theplates changes, the electrical field between the plates changesaccordingly, and results in electrical signal output variationproportional to the mass variation of the strand.4.4 Evenness is always expressed as variation betweensuc
18、cessive lengths L and over a total length Ls. When the Lcevenness is measured, it corresponds to the length capacitancezone width, i.e., 8 mm (0.3 in) for yarns, 12 mm (0.5 in) forrovings and fine slivers, and 20 mm (0.8 in) for slivers that arereferred to as short-term evenness. Longer-term evennes
19、s mayalso be evaluated by electronically increasing Lc.5. Summary of Test Method5.1 A textile strand is passed through a length capacitancezone of an evenness tester at a constant speed. The massvariation of successive interval lengths is measured and fromwhich other values of evenness are derived:
20、coefficient ofvariation, short-, mid- and long-term variations, and imperfec-tions.6. Significance and Use6.1 This test method for the determination of evenness oftextile strands is used extensively for acceptance testing ofcommercial shipments of filament or spun staple yarn, comberlaps, roving, sl
21、iver, or tops. 6.2 6.3 6.4 6.5 Evenness valuesobtained on different instruments will be comparable forstrands from the same sample provided the following param-eters are the same in all cases: (1) the measure of evennessused; (2) the capacitive length zone L (see 3.1.5 and 3.1.5.1);(3) the sample le
22、ngth, Ls (see 3.1.8); (4) instrument test speed,(5) laboratory temperature and humidity conditions (see 12.1and 12.1.1); and (6) test specimen variation. When differentmodels of an instrument are used, and one or more of the sixparameters are not identical, test results may differ.6.2 Values of stra
23、nd evenness are also used in qualitycontrol, process optimization, and together with yarn strengthmeasurements, is the first appraisal of a strands quality. A lowevenness value is, in general, preferred. Higher evennessvalues generally indicate difficult spinning, lower yarnstrength, and poorer fabr
24、ic appearance. Experience has shownthat the relationship of evenness to the prediction of yarnperformance and to fabric appearance is not a simple one. Anevenness value must, therefore, be used cautiously and besupplemented by additional evenness information, such asmid-term and long-term mass varia
25、tions, thin, thick, and nepimperfection counts, diagram chart spectrogram chart, lengthvariation curve, and histogram analyses.6.3 Continuous filament yarns should be tested for massvariation on instruments specifically designed to them.; failureto do so will result in inaccurate test results. Furth
26、er, low-twist,continuous yarns tend to flatten to a ribbon configuration whilepassing through the condenser of a capacitance instrument.These specific instruments are designed to insert false twist inthe condenser during testing to overcome the flattening effectand may result in false variation read
27、ings.6.4 Strands made from fiber blends should be tested only ifthe different fibers are uniformly distributed throughout thestrand. Non-uniform blending may cause a higher reading ofmass variation than the true value if the component fibers differin dielectric constant (see 3.1.1 and 3.1.1.1).6.5 E
28、venness values obtained on different instruments willbe comparable for strands from the same sample provided thefollowing parameters are the same in all cases: (1) the measureof evenness used; (2) the capacitive length zone L (see 3.1.5and 3.1.5.1); (3) the sample length, Ls (see 3.1.8); (4) instru-
29、ment test speed, (5) laboratory temperature and humidityconditions (see 12.1 and 12.1.1); and (6) test specimen varia-tion. When different models of an instrument are used, and oneor more of the six parameters are not identical, test results maydiffer.6.6 If there are any differences of practical si
30、gnificancebetween reported test results for two (or more) laboratories,comparative test should be performed using competent statis-tical assistance and an agreed upon number of samples that arehomogeneous and randomly assigned, should be used toD1425/D1425M 0912determine if there is a statistically
31、significant difference be-tween them. If a bias is found, either its cause must be foundand corrected, or future testing for that material must beadjusted in consideration of the statistically significant differ-ences found.7. Apparatus7.1 Capacitance-Type Unevenness Testing InstrumentsAtextile stra
32、nd evenness tester that utilizes the electronic capaci-tance measuring principle.7.1.1 Differences between older and newer capacitancetesters for calibration, recording devices, test settings, and dataoutput can be found in the manufacturers instruction manualfor specific models.7.2 Package holders,
33、 guides, tension devices, and take-upmechanismsDevices and attachments to evenness testinginstruments that aid in the uniform delivery of the strand atspecified speed, without undue acceleration or deceleration, ata reasonably constant tension. These devices are especiallycritical for loose textile
34、strands such as sliver, roving, andcomber laps7.3 Recording device Printer or computer-generated filesfrom which numeric and graphic test data can be produced.7.4 Twist insertion deviceA mechanism in the condenserzone of an evenness testing instrument that inserts false twistinto continuous filament
35、 yarns8. Sampling8.1 Unless otherwise agreed upon, as when specified in anapplicable material specification, take a lot sample and labo-ratory sample as directed in Practice D22588.2 Typical spun yarn sample lots are ten or twenty pack-ages. Unless otherwise agreed upon, as when specified in anappli
36、cable material specification, take a lot sample and labo-ratory sample as directed in.9. Number of Specimens9.1 Conduct test on one strand from each yarn package inthe sample lot.9.2 Test three strands from silver, roving, comber laps ortops or the recommended number of equipment manufacturer.10. Co
37、nditioning10.1 Condition strands according to Practice D1776. Pre-conditioning is not required unless in the case of dispute.10.2 For yarn, the time required for conditioning dependson the fiber, the size of the package and the compactness of theyarn wound on the package. Further, a shorter conditio
38、ningtime may be sufficient if only the outside layer of a yarnpackage is to be tested than if the whole package is to be tested.As a general guide, condition tightly wound yarn packages for48 h. Other strands such as sliver, roving, and laps may notrequire conditioning and can be tested as soon as t
39、hey arebrought into the laboratory.10.3 If the standard atmosphere described in Practice D1776is not available, condition the strand in a stable atmosphere inwhich the test is to be performed until it has reached equilib-rium. Record the conditions under which the test was per-formed.10.4 Test resul
40、ts may not be comparable if conditioned andtested in different atmospheres.11. Selection of Testing Parameters11.1 Measure of UnevennessRecommended evaluationtest times and strand speeds are listed in Table 1.11.1.1 The selection of test speeds is important to avoidstretching strands during the test
41、 length and is specific to thetype of strand and the model of capacitance tester used. Yarnscan normally be tested at higher speeds than yarn intermediatessuch as sliver or roving. In general, the testing speed setting forsliver and tops is 25 m/min (25 yd/min). Higher rates can beused if the test i
42、nstrument is equipped with a poweredunwinding device or the material does not exhibit any addi-tional mass variation caused by stretching at the selected speed.The testing speed rate setting for roving is 50 m/min (50yd/min) and for yarns either 100, 200, 400, or 800 m/min (100,200, 400, or 800 yd/m
43、in).11.1.2 Imperfection evaluations are conducted on stapleyarns only. The range of possible measurements for countingimperfections is shown in Table 2. Select a measurementsetting for each imperfection category. Different yarn spinningsystems and other fiber and yarn processes will influence whichs
44、ettings to select. See Table 3.11.2 Check the manufacturers instructions for other selec-tions such as chart speeds if not using a newer tester.12. Procedure12.1 Check the manufacturers instructions for calibrationprocedures if not automatically performed by the model used.TABLE 1 Recommended Strand
45、 Speeds and Evaluating TimesMaterial Strand Speed Evaluating TimeTop or sliver 4 m/min (4 yd/min) 5 or 10 minSliver or roving 8 m/min (8 yd/min) 5 or 10 minSliver or roving 25 m/min (25 yd/min) 5 or 10 minSliver 50, 100 m/min (50,100yd/min)A1 or 2.5 minRoving 50, 100, 200 m/min (50,100, 200yd/min)2.
46、5 or 5 minYarn 400, 800Bm/min (400,800 yd/min)0.5 ,1.0, 1.25 or 2.5 minFilament Yarns 400 or 800 m/min (400or 800 yd/min)2.5 minAThis speed may be used if the sliver specimen is not stretched or if a poweredunwinding apparatus is used.BThe 800 m/min or yd/min testing speed is not available on all in
47、struments.D1425/D1425M 091312.2 Mount conditioned package(s) on a suitable holder orcreel truck as described by the instrument manufacturer.Follow the manufacturers instructions for threading yarn intothe capacitance zone or through automatic thread guides.12.2.1 When testing yarn from packages, the
48、 yarn should bepulled from the packages in the same direction (clockwise orcounterclockwise). Filament yarns will require specific thread-ing instructions from the manufacturer.12.2.2 The threading-up procedures for sliver, roving,comber laps, and tops are extremely critical.12.3 Each strand should
49、be tested in one uninterrupted run.13. Calculation13.1 For older capacitance testers, the final CV% or U% isread from the recording device.13.1.1 If more than one value of CV% or U% is obtainedper individual package, then calculate the average value ofevenness for each package.13.1.2 Calculate the average of CV% or U% for all pack-ages.13.1.3 If requested, calculate the coefficient of variation orthe standard deviation (or both) of the CV% or U% valuesobtained for each package to determine between packagevariation.13.2 For newer capacitance testers, all calculat
