1、Designation: D 1425/D1425M 09Standard Test Method forUnevenness of Textile Strands Using Capacitance TestingEquipment1This standard is issued under the fixed designation D 1425/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.1. Scope1.1 This test method covers the indirect measurement ofevenness (mass variation) of non-conductive textile s
3、trands,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 different fibers are uniformly distributedthroughout the st
4、rand.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 andgraphical representations of evenness values in the form
5、 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; therefore, eachsystem shall be used independently of the other.
6、 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 standard to establish appro-priate safety and health practices an
7、d determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 123 Terminology Relating to TextilesD 1776 Practice for Conditioning and Testing TextilesD 2258 Practice for Sampling Yarn for TestingD 4849 Terminology Related to Yarns and Fibers3. Te
8、rminology3.1 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 plates.3.1.1.1 DiscussionThe dielectric change is measur
9、ed 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% (or U%), n in textiles, the coeffi-cient of mass vari
10、ation 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 CV% and U% is U% ismultiplied by 1.25. Although both C
11、V% 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 places, and neps of asample strand length measured by a
12、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 having a high ratioof length to diameter and normally us
13、ed 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 value that is the cumulative number thicks, thins, andneps
14、 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 D 123 and Terminology D 4849.4. Basic Principles of Test Method4.1 Properties of strand irregularity measured along itslength are measured in terms
15、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 tech-nique is an indirect testing method. The accuracy
16、 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 capacitor plates(measuring slots). If the mass of a strand
17、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 betweensuccessive lengths L and over a total length Ls. When t
18、he 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 evenness mayalso be evaluated by electronically increasing
19、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: coefficient ofvariation, short-, mid- and long-term
20、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, sliver, or tops. 6.2 6.3 6.4 6.5 Evenness valuesobtain
21、ed 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 length, Ls (see 3.1.8); (4) instrument test speed,(5)
22、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 strand evenness are also used in qualitycontrol, process
23、 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 fabric appearance. Experience has shownthat the relation
24、ship 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 variations, thin, thick, and nepimperfection counts, diag
25、ram 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. Further, low-twist,continuous yarns tend to flatten to a
26、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 readings.6.4 Strands made from fiber blends should be te
27、sted 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 Evenness values obtained on different instruments wil
28、lbe 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-ment test speed, (5) laboratory temperature and humi
29、dityconditions (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 significancebetween reported test results for two (or
30、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 toD 1425/D1425M 092determine if there is a statistically significant difference be-tween them. If a bias is f
31、ound, 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 strand evenness tester that utilizes the electronic capa
32、ci-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, guides, tension devices, and take-upmechanismsDevic
33、es 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 strands such as sliver, roving, andcomber laps7.3 Re
34、cording 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 yarns8. Sampling8.1 Unless otherwise agreed upon, a
35、s when specified in anapplicable material specification, take a lot sample and labo-ratory sample as directed in Practice D 22588.2 Typical spun yarn sample lots are ten or twenty pack-ages. Unless otherwise agreed upon, as when specified in anapplicable material specification, take a lot sample and
36、 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. Conditioning10.1 Condition strands according to Pract
37、ice D 1776. 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 conditioningtime may be sufficient if only the outside lay
38、er 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 they arebrought into the laboratory.10.3 If the sta
39、ndard atmosphere described in PracticeD 1776 is not available, condition the strand in a stableatmosphere in which the test is to be performed until it hasreached equilibrium. Record the conditions under which thetest was performed.10.4 Test results may not be comparable if conditioned andtested in
40、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 length and is specific to thetype of strand and the
41、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 instrument is equipped with a poweredunwinding device
42、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/min).11.1.2 Imperfection evaluations are conducted on
43、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 whichsettings to select. See Table 3.11.2 Check the manufac
44、turers 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.12.2 Mount conditioned package(s) on a suitable holder orcreel truck as describ
45、ed by the instrument manufacturer.TABLE 1 Recommended Strand 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)
46、11 or 2.5 minRoving 50, 100, 200 m/min (50,100, 200yd/min)2.5 or 5 minYarn 400, 8002m/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 minD 1425/D1425M 093Follow the manufacturers instructions for threading yarn intothe capacitance zone or through au
47、tomatic thread guides.12.2.1 When testing yarn from packages, the 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,comb
48、er laps, and tops are extremely critical.12.3 Each strand should 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
49、 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 calculations andreports are automatically produced.14. Report14.1 State the test was performed according to ASTMD1425.14.2 Test instruments make, model, year, and type ofintegrator, if used.14.3 Lot, sample and product identification.14.4 Number o
