1、Designation: D 6720 07Standard Test Method forEvaluation of Recoverable Stretch of Stretch Yarns (SkeinMethod)1This standard is issued under the fixed designation D 6720; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the recov-erable stretch of commercial textured yarns, covered elasto-me
3、ric yarns and other stretch yarns using skeins. This testmethod is particularly valuable for yarns that develop addi-tional crimp upon exposure to hot, wet conditions. Therecoverable stretch is a relative measure of the recovery powerthe yarn can be expected to provide in a finished fabric.1.2 This
4、test method is applicable to continuous filamentyarns and is suitable for yarns that develop additional stretchpotential upon exposure to heat.1.3 This method is applicable to yarns 500 denier or finer.1.4 The values stated in SI units are to be regarded asstandard. The values given in parentheses a
5、re provided forinformation only.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 and determine the applica-bility of regulatory limitati
6、ons prior to use.2. Referenced Documents2.1 ASTM Standards:2D 123 Terminology Relating to TextilesD 1776 Practice for Conditioning and Testing TextilesD 4849 Terminology Relating to Yarns and Fibers3. Terminology3.1 For all terminology relating to D13.58, Yarns andFibers, refer to Terminology D 4849
7、.3.1.1 The following terms are relevant to this standard:elastomeric yarn, recoverable stretch, stretch yarn.3.2 For all other terms are related to textiles, refer toTerminology D 123.4. Summary of Test Method4.1 A skein of yarn is prepared by winding a prescribednumber of turns on a reel in order t
8、o obtain a 5000 g skein. Theskein is immersed in boiling water for 15 min and air dried toallow the yarn skein to fully develop its stretch (crimp)potential. The skein is exercised under a specified tension andits extended length is recorded. A lessor tension is then appliedto the skein and its reco
9、very length is recorded. The recover-able stretch is calculated from the difference between therecorded length measurements and expressed as a percentageof the recovery length.5. Significance and Use5.1 This test method is considered satisfactory for accep-tance testing of commercial shipments becau
10、se current esti-mates of between-laboratory precision are acceptable and themethod is used extensively in the trade for acceptance testing.5.1.1 If there are differences of practical significance be-tween reported test results for two laboratories (or more),comparative tests should be performed to d
11、etermine if there isa statistical bias between them, using competent statisticalassistance. As a minimum, use samples for such comparativetests that are as homogeneous as possible, drawn from the samelot of material as the samples that resulted in disparate resultsduring initial testing, and randoml
12、y assigned in equal numbersto each laboratory. The test results from the laboratoriesinvolved should be compared using a statistical test forunpaired data, at a probability level chosen prior to the testingseries. If bias is found, either its cause must be found andcorrected, or future test results
13、for that material must beadjusted in consideration of the known bias.5.2 This test differs from other crimp contraction testmethods in that it measures the recoverable stretch during theunload cycle of the yarn.1This test method is under the jurisdiction of ASTM Committee D13 on Textilesand is the d
14、irect responsibility of Subcommittee D13.58 on Yarns and Fibers.Current edition approved Jan. 1, 2007. Published January 2007. Originallyapproved in 2001. Last previous edition approved in 2001 as D 6720 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer
15、 Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Interferences6.1 Care should be take
16、 to ensure that the skein is not liftedpast the point where it is supported by the yarn. If the 30 gweight is lifted beyond this point, a false reading will resultsince the yarn will be on the next cycle load extension force.7. Apparatus7.1 ReelAhand or motor driven reel having a perimeter of1.37 m
17、(54 in.).7.2 Water Bath Tank, filled with water, minimum dimen-sions, 50 l capable of maintaining 100 6 1C (212 6 2F),for boiling off skeins.7.3 Rack, having parallel pegs or bars placed a sufficientdistance apart to hold the skeins extended to nearly their fulllength without stretching, kinking or
18、entangling the yarns.7.4 Measuring Scales, consisting of one meter stick or otherscale for each peg position on the rack, having measuringintervals of 1 mm (0.05 in.), mounted vertically with a hook atthe top aligned with the scales 0 position.7.5 Clock or Stopwatch, with second intervals.7.6 Tensio
19、n WeightsA 30 g weight and either a 1000 g or2 - 500 g weights, having tolerances of 1 %. Metal tongs, toremove skeins from water bath.8. Sampling, Test Specimens, and Test Units8.1 Lot SampleAs a lot sample for acceptance testing,take a random number of shipping units directed in a applicablemateri
20、al specification or other agreement between the pur-chaser and the supplier, such as an agreement to use PracticeD 2258. Consider shipping cases or other shipping units to bethe primary sampling units.NOTE 1An adequate specification or other agreement between thepurchaser and the supplier requires t
21、aking into account the variabilitybetween shipping units, between packages or ends within a shipping unit,and between specimens from a single package to provide a sampling witha meaningful producers risk, consumers risk, acceptable quality leveland limiting quality level.8.2 Laboratory SampleAs a la
22、boratory sample for accep-tance testing, take at random from each shipping unit in the lotsample the number of packages as directed in applicablespecification or as agreed to between purchaser and supplier.8.3 Test SpecimensPrepare 5000 denier skeins using awinding tension of about 0.1 gf/d. Test on
23、e skein from eachpackage in the laboratory sample. In any event, test a minimumof three packages.9. Conditioning9.1 No preconditioning is required.9.2 After exposure in the water bath, condition skeinsamples as directed in Practice D 1776 for a minimum of 16hrs. at 21 + 1C (70 + 2F) and 65 + 2 % rel
24、ative humidity.10. Preparation of Test Equipment and Calibration10.1 Ensure tension weights are within 1 % of assignedvalue.10.2 Ensure that water bath temperature measuring devicesare within calibration.10.3 Bring bath water to 100 6 1C (212 6 2F).11. Procedure11.1 Immerse the test specimen skeins
25、in boiling water 1006 1C (212 6 2F) for 15 min to allow development of crimppotential.11.2 Air dry the skeins on the rack and conditioned asdirected in 9.2.11.3 After drying, hang each skein on the meter stick hooks.11.4 Gently, apply both the 30 g and 1000 g tension weightsto the bottom of the skei
26、n.11.5 After about 10 s, allow the skein to relax by manuallysupporting the weights by hand, so that it becomes slack.11.6 After 10 s, allow the skein to gently extend downwardunder the 1030 g weight.11.7 After about 10 s, allow the skein to relax by manuallysupporting the weights by hand, so that i
27、t becomes slack.11.8 After 10 s, reapply the force by letting the skein gentlyextend under the weight of the 1030 g force.11.9 After 10 s, record the extended length, L1, to thenearest 1 mm (0.05 in.) while under the 1030 g tension.11.10 Place two fingers into the bottom of the skein loopjust above
28、the 30 g weight to prevent snap back while holdingthe relative extended position of the skein and carefully removethe other weights totaling 1000 g.11.11 Allow the skein to gradually recover under the 30 gtension, without bouncing or lifting beyond its recovery length,guided by the fingers as they l
29、eave the loop.NOTE 2Care should be taken to ensure that the skein is not lifted pastthe point where it is supported by the yarn. If the 30 g weight is liftedbeyond this point, a false reading will result since the yarn will be on thenext cycle load extension force.11.12 After resting for 30 s, recor
30、d the unload recoverylength to the nearest 1 mm (0.05 in.) while under the 5.4mgf/dtex (30 g) tension, L2.12. Calculation or Interpretation of Results12.1 Calculate the Recoverable Stretch for each test speci-men to the nearest 0.01 percent according to Eq 1:L1 L2! / L2* 100 (1)where:L1= extended le
31、ngth after the third load cycle with 185mgf/dtex (1030 g) force on the yarn., (from 11.9), andL2= unload recovery length after the third load cycle with5.4 mgf/dtex (30 g) force on the yarn, (from 11.12).12.2 Calculate the average recoverable stretch to the nearest0.01 percent for the lot.13. Report
32、13.1 State that the specimens were tested as directed in TestMethod 6720. Describe the materials or products sampled.13.2 Report the following information:13.2.1 Recoverable Stretch.14. Precision and Bias14.1 An interlaboratory study was performed in November2000 to estimate variability of the test
33、method. The studyincluded two laboratories. Two operators were used in eachlaboratory to measure three specimens for five different yarnsD6720072that develop crimp in hot wet conditions on two different days.ANOVA was used to determine variance components.14.2 Method repeatability is defined as the
34、“maximumdifference” that can “reasonably” be expected between two testresults obtained on the same material when the test results areobtained in the same laboratory. Repeatability standard devia-tion, sr, is taken to be the square root of the “specimen”variance component, and represents within-opera
35、tor precision.Method reproducibility is defined as the “maximum difference”that can “reasonably” be expected between two test resultsobtained on the same material when the test results areobtained from different laboratories.3sR, the total standarddeviation, is formed by taking the square root of th
36、e sum ofintra- and inter-laboratory variance components.NOTE 3Because the interlaboratory test included less than the recom-mended five laboratories, estimates of precision data in Tables 1 and 2may be either underestimated or overestimated to a considerable extentand should be used with special cau
37、tion.14.3 BiasThe procedure of this test method produces atest value that can be defined only in terms of a test method.There is no independent, referee method by which bias may bedetermined. This test method has no known bias.15. Keywords15.1 crimp; elastomeric yarns; recoverable stretch; stretchya
38、rns; textured yarnsASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement
39、of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for
40、 additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known
41、to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM a
42、t the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).3John Mandel and Theodore W. Lashof, 1987. The Nature of Repeatability andReproducibility. Jour. Quality Technology, 19 (1).TABLE 1 Recoverable Stretch, Average P
43、ercent and Componentsof Variation expressed as Squares of Standard DeviationNOTEResponse = Recoverable Stretch, %.Material Average V(lab) V(operator) V(date) V(specimen)2GT 22.53083 0.00000 1.55343 0.19143 0.385004GT 24.20042 3.65089 0.12216 0.11723 0.61726Nylon 66 17.19917 2.16506 0.00000 0.41629 0
44、.52026Covered LycraT 80.21542 0.00000 34.61043 4.93616 4.44413InspiraT 20.72083 25.78378 0.00000 16.93464 0.96332TABLE 2 Repeatability and Reproducibility for RecoverableStretch of Stretch Yarns Expressed as Standard DeviationPercentage PointsNOTEResponse = Recoverable Stretch, %.Material srRepeatability sRReproducibility2GT 0.62 1.72 1.46 4.054GT 0.79 2.18 2.12 5.88Nylon 66 0.72 2.00 1.76 4.88Covered LycraT 2.11 5.84 6.63 18.39IspiraT 0.98 2.72 6.61 18.32D6720073
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