1、Designation: D1422 99 (Reapproved 2008)D1422/D1422M 13Standard Test Method forTwist in Single Spun Yarns by the Untwist-Retwist Method1This standard is issued under the fixed designation D1422;D1422/D1422M; the number immediately following the designation indicatesthe year 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. Scope1.1 This test method2 describes the determination of twist in single spun yarns when o
3、nly an approximation of the true twistis required.NOTE 1For a more accurate method see Test Method D1423.1.2 This test method is applicable to spun single yarns in continuous lengths, and also to spun yarns raveled from fabrics,provided specimens at least 200 mm (8 in.)8 in. long can be obtained.1.3
4、 The values stated in either inch-pound or SI units are to be regarded separately as standard. Within the text, the SI units areshown in parentheses. The values stated in each system are not exact equivalents; therefore each system shall be usedindependently of the other. Combining values from the t
5、wo systems may result in nonconformance within this test method.1.3 This test method has been found satisfactory for use in determining the approximate twist content in all single ring spunyarns and 100% cotton open-end yarns. For all open-end spun yarns that are not 100 % cotton this test method ha
6、s not been foundto be satisfactory for determining twist but may be used to measure deviation from an average value.of all types and fiber contents,but not in open-end spun yarns.1.4 This specification shows the values in both inch-pound units and SI units. The “inch-pound” units is the technically
7、correctname for the customary units used in the United States. The “SI” units is the technically corrected name for the system of metricunits known as the International System of Units. The values stated in either acceptable metric SI units or in other units shallinch-pound units are to be regarded
8、separately as standard. The values expressedstated in each system may not be exactequivalents; therefore, each system mustshall be used independently of the other, without combining in any way. other. Combiningvalues from the two systems may result in non-conformance with the standard.1.5 This stand
9、ard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations priorto use.2. Referenced Documents2.1 ASTM Standards:3
10、D123 Terminology Relating to TextilesD1059 Test Method for Yarn Number Based on Short-Length Specimens (Withdrawn 2010)4D1423 Test Method for Twist in Yarns by Direct-CountingD2258 Practice for Sampling Yarn for TestingD3888 Terminology for Yarn Spinning SystemsD4849 Terminology Related to Yarns and
11、 Fibers3. Terminology3.1 Definitions:1 This test method is under the jurisdiction of ASTM Committee D13 on Textiles and is the direct responsibility of Subcommittee D13.58 on Yarns and Fibers.Current edition approved Aug. 1, 2008July 1, 2013. Published October 2008August 2013. Originally approved in
12、 1956. Last previous edition approved in 19992008 asD1422 99.D1422 99(2008). DOI: 10.1520/D1422-99R08.10.1520/D1422_D1422M-13.2 This test method is commonly designated by the less precise term“ Untwist-Twistterm “Untwist-Twist Method.”3 For referencedASTM standards, visit theASTM website, www.astm.o
13、rg, 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.4 The last approved version of this historical standard is referenced on www.astm.org.This document is not an ASTM standard an
14、d is intended 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
15、the current 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 direction of twist, nthe right or left direction of the helix formed in a twisted
16、strand as indicated by superimposition ofthe capital letter “S” or “Z.”3.1.1.1 DiscussionYarn has S twist if, when the yarn is held in a vertical position, the visible spirals or helices around its central axis conform indirection of slope to the central portion of the letter“ S,” and Z twist if the
17、 visible spirals or helices conform in direction of slopeto the central portion of the letter “Z.” When two or more yarns, either single or plied, are twisted together, the letters “S” and “Z”are used in a similar manner to indicate the direction of the last twist inserted.3.1.2 single yarn, nthe si
18、mplest strand of textile material suitable for operations such as weaving, knitting, etc.3.1.2.1 DiscussionA single yarn may be formed from fibers with more or less twist; from filaments with or without twist; from narrow strips ofmaterials such as paper, cellophane, or metal foil; or from monofilam
19、ents. A yarn which is either twistless or can be renderedtwistless in a single untwisting operation. When twist is present, it is usually all in the same direction.3.1.3 spun yarn, nin a staple system, a continuous strand of fibers held together by some binding mechanism.3.1.3.1 DiscussionThe bindin
20、g mechanism most commonly used in spun yarns is twist. Other useful mechanisms that are used are chemical additives,wrapping, entanglement, or some combination of these. Test Method D1422 is applicable only to yarns which have twist.3.1.4 twist, nin textile strands, the helical or spiral configurati
21、ons induced by turning a strand about its longitudinal axis.3.1.4.1 DiscussionTwist is usually expressed as the number of turns about the axis that are observed in a specified length either metres (tpm) or inches(tpi).3.1.5 twist factor, TF,nthe product obtained when the twist expressed in turns per
22、 centimetre is multiplied by the square rootof the yarn number expressed in tex:Twist factor TF!5tpcm3=T (1)where:T = yarn number expressed in tex.3.1.5.1 DiscussionTwist multiplier and twist factor are a measure of the “twist hardness” of yarn because they are approximately proportional to thetange
23、nt of the angle between fibers on the outer yarn surface and the axis of the yarn; the larger this angle, the harder the twist.Furthermore, this angle is a function of both the twist content (turns per unit length) and the number of fibers per yarn cross section(yarn number). Hence, twist content al
24、one cannot provide a measure of the twist hardness of a yarn. Twist multiplier and twistfactor are proportional to each other and differ only in the units used.The two are related by Eq 2 and Eq 3:TF5k 3TM (2)k 5277.29/=L (3)where:L = length in yards of the hank used to define the indirect yarn numb
25、er of the type,N = hanks/lb. In particular for cotton count,k = 9.567 so that Eq 2 becomes Eq 4:TF59.5673TM (4)3.1.6 twist multiplier, TM,nthe quotient of the twist expressed in turns per inch and the square root of the yarn number in anindirect system.Twist multiplier TM!5tpi/=N (5)D1422/D1422M 132
26、where:N = yarn number in an indirect system, the cotton system unless otherwise specified.3.1.7 yarn, na generic term for a continuous strand of textile fibers, filaments, or material in a form suitable for knitting,weaving, or otherwise intertwining to form a textile fabric.3.1 For Refer to Termino
27、logy D4849 for definitions of other textilethe following terms used in this test method, refer toTerminologystandard: direction of twist, single D123. yarn, spun yarn, twist, twist factor, twist multiplier, and yarn.3.2 Refer to Terminology D123 and Terminology D3888 for definitions of other terms u
28、sed in this standard.4. Summary of Test Method4.1 A specimen is untwisted and then retwisted in the opposite direction until it contracts to its original length. It is assumedthat the same amount of twist has been inserted as was originally present. Twist, as turns per unit length, is calculated as
29、half thenumber of turns registered on the counter divided by the specimen length.5. Significance and Use5.1 This test method is used for acceptance testing in the trade for economic reasons even though it is less accurate than thedirect method, Test Method D1423.5.1.1 If there are differences or pra
30、ctical significance between reported test results for two laboratories (or more), comparativetests should be performed to determine if their is a statistical bias between them, using competent statistical assistance. As aminimum, the test samples should be used that are as homogeneous as possible, t
31、hat are drawn from the material from which thedisparate test results are obtained, and that are assigned randomly in equal numbers to each laboratory for testing. Other materialswith established test values may be used for this purpose. The test results from the two laboratories should be compared u
32、sing astatistical test for unpaired data, at a probability level chosen prior to the testing series. If a bias is found, either its cause must befound and corrected, or future test results must be adjusted in consideration of the known bias.5.2 The “setting” of twist in some fibers causes excessive
33、contraction when the yarn is retwisted in the reverse direction.Therefore, the number of turns required to bring the specimen back to its original length may be less than the number of turnsremoved in untwisting. This effect may be partially offset by the use of higher pretensioning loads; but this
34、increases the dangerof stretching the yarn. Little information is available on the correct tensions to use for yarns made from different fibers or withdifferent amounts of twist.5.3 In addition to being less tedious, this test method requires fewer specimens than the direct-counting method and the r
35、esultsmay be sufficiently accurate for certain purposes. This test method can be useful in those cases where the main objective is tomeasure variations from an average value.Another possible application is where a large amount of twist testing is required on yarnsof similar type and twist. In this c
36、ase preliminary tests comparing this method and the direct method could be used to determinethe correct pretension.5.4 Twist has important effects on the physical properties of yarn. Low-twist yarn is lofty and is usually preferred for knittingbecause of its softness, covering power, and warmth. Inc
37、reasing the amount of twist causes an increase in yarn strength byincreasing fiber cohesion, but as the twist angle increases beyond an optimum point, strength decreases due to a loss in effectivefiber contribution. Maximum yarn strength is obtained by inserting a medium amount of twist to obtain an
38、 optimum balancebetween these two opposing forces. High twist produces yarns of high density (“hard” or “wiry”) and high elongation and mayimprove the abrasion and impact resistance of fabrics.5.5 The optimum twist for either manufacturing efficiency or physical properties usually increases as stapl
39、e length decreases.5.6 The twist in a yarn before it is packaged may be different from that of the yarn after it has been withdrawn from the packagebecause of changes in tension and the effect of the method of withdrawal. Withdraw the yarn from the package in the directionof normal use, either from
40、the side or over-end. If the yarn is withdrawn over-end, a slight increase or decrease in twist will takeplace, depending upon the direction of the twist in the yarn, the direction of winding on the package, and the length of the turn(or wrap) on the package.NOTE 2The difference in twist between unw
41、inding from the side and over-end is 1/pid, where d is the diameter of the package.5 Thus, for a 25-mm(1-in.)1-in. diameter package, the difference would be about 13 tpm or about one third tpi.5.7 When a yarn is taken from a more complex yarn structure or from a fabric, the resultant twist should be
42、 considered onlyan approximation of the original value because of alterations that may have occurred as a result of the effects of unwinding,handling, and mechanical strains met in processing.5 Woods, H. J., “The Kinematics of Twist, I, The Definition of Twist,” Journal of Textile Science, JTBIA, vo
43、l 4, 1931, 3336.D1422/D1422M 1336. Apparatus6.1 Twist Tester, consisting of a pair of clamps, one of which is rotatable in either direction and positively connected to arevolution counter. The tester may be hand- or power-driven. The position of one clamp (or both clamps) shall be adjustable toaccom
44、modate specimens having the length prescribed in 10.2. The tester shall be provided with a variable tensioning device soconstructed that a specific force may be applied to the specimen at the beginning and end of the test and removed completely duringthe intervening untwisting and twisting operation
45、s.6.2 Dissecting needle or stylus.6.3 Metal ruler to verify gagegauge length (accurate to 2 mm or 0.1 in.).0.1 in.).7. Sampling7.1 Lot SampleSelect one or more shipping units taken at random to represent an acceptance sampling lot and used as a sourceof laboratory samples.7.2 Laboratory SampleFor pa
46、ckaged yarns, take a minimum of five packages for the laboratory sample unless otherwiseagreed upon between purchaser and seller. For yarns from woven or knitted fabrics, the sample must be large enough to furnishspecimens of the length and number specified in 7.3.3.7.3 Selection of Specimens:7.3.1
47、As nearly as possible take an equal number of specimens from each package or unit of the laboratory sample. Take thespecimens from each package in a random manner to minimize the effect of cyclic variations introduced during manufacturingprocesses. When preparing specimens, conditioning them, or ins
48、erting them in the tester, take care to avoid any change in twist.7.3.2 For packaged yarns, remove and discard the first 25 m (25 yd)25 yd of yarn. Using a minimum of tension, takespecimens at random intervals greater than 1 m (1 yd)1 yd along the yarn. Withdraw the yarn from the package in the dire
49、ctionof normal use, either from the side or over-end, if known. If the direction is not known, withdraw the yarn from the side (Note2). When more than five specimens are taken from an individual package, take groups of five or less at intervals of several yards.Do not cut the specimen free from the package or from the yarn to be discarded until after the yarn is secured in the clamps ofthe twist tester. When possible, take the specimen from near the center of the traverse and not at the traverse reversals.7.3.3 For woven fabric, take warp specimens
