ASTM_D_6720_-_07_2012.pdf

Designation:D672007(Reapproved 2012)Standard Test Method forEvaluation of Recoverable Stretch of Stretch Yarns(SkeinMethod)1This standard is issued under the fixed designation D6720;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()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-meric 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 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 are 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 limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD1776 Practice for Conditioning and Testing TextilesD4849 Terminology Related to Yarns and Fibers3.Terminology3.1 For all terminology relating to D13.58,Yarns andFibers,refer to Terminology D4849.3.1.1 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 D123.4.Summary of Test Method4.1 A skein of yarn is prepared by winding a prescribednumber of turns on a reel in order to 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 recovery 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 because 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 determine 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 randomly 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 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.6.Interferences6.1 Care should be take to ensure that the skein is not liftedpast the point where it is supported by the yarn.If the 30 g1This test method is under the jurisdiction ofASTM Committee D13 on Textilesand is the direct responsibility of Subcommittee D13.58 on Yarns and Fibers.Current edition approved July 1,2012.Published August 2012.Originallyapproved in 2001.Last previous edition approved in 2007 as D6720 07.DOI:10.1520/D6720-07R12.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 weight 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(54 in.).7.2 WaterBathTank,filledwithwater,minimumdimensions,50 l capable of maintaining 100 6 1C(212 62F),for boiling off skeins.7.3 Rack,having parallel pegs or bars placed a sufficientdistance apart to hold the skeins extended to n