1、BRITISH STANDARD BS ISO 17202:2002 Textiles Determination of twist in single spun yarns Untwist/retwist method ICS 59.080.20 BS ISO 17202:2002 This British Standard, having been prepared under the direction of the Materials and Chemicals Sector Policy and Strategy Committee, was published under the
2、authority of the Standards Policy and S t r a t e g y C o m m i t t e e o n 25 November 2002 BSI 25 November 2002 ISBN 0 580 40805 1 National foreword This British Standard reproduces verbatim ISO 17202:2002 and implements it as the UK national standard. The UK participation in its preparation was e
3、ntrusted to Technical Committee TCI/24, Physical testing of textiles, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in t
4、his document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a c
5、ontract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposal
6、s for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 10, an inside back cover
7、 and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments Reference number ISO 17202:2002(E)INTERNATIONAL STANDARD ISO 17202 First edition 2002-11-01 Textiles Determination of twist in
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13、irypthgiso.c h Web ww.wiso.ch Printi denS witlrez dnaii I SO 2002 Allr ithgsr esedevrBSISO17202:2002iiIS:20271 O2002(E) I SO 2002 All irthgs ersedevr iiiContents Page Foreword iv Introduction. v 1 Scope 1 2 Normative references 1 3 Terms and definitions. 2 4 Principle . 2 5 Apparatus. 3 6 Standard a
14、tmosphere . 3 7 Sampling 4 8 Test Specimens . 4 9 Procedure 1 Determination of direction of twist . 5 10 Procedure 2 Determination of amount of twist . 5 11 Calculations . 7 12 Test report 8 Annex A (informative) Suggested procedure for sampling 9 Bibliography 10 BSISO17202:2002iiiIS:20271 O2002(E)
15、vi I SO 2002 All irthgs ersedevrForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body inter
16、ested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
17、 Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the te
18、chnical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of pat
19、ent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 17202 was prepared by Technical Committee ISO/TC 38, Textiles, Subcommittee SC 23, Fibres and yarns. Annex A of this International Standard is for information only. BSISO17202:2002ivIS:20271 O2002(E) I S
20、O 2002 All irthgs ersedevr vIntroduction The direct twist method (see 1 and 2) has, for a long time, been recognized as the most accurate method of twist determination but the much faster untwist/retwist method has long been used in industry in many countries. In the 1980s the hope was expressed by
21、some Institutes that the untwist/retwist method would be suitable for the measurement of twist of open-end yarns that cannot be measured by the direct method. First experiments in the 1970s and later in the 1990s showed, however, that the untwist/retwist method is not suitable to OE yarns. The prese
22、nt method is therefore restricted to ring spun yarns. BSISO17202:2002vINTENRATIONAL TSANDADR IS:20271 O2002(E)I SO 2002 All irthgs ersedevr 1Textiles Determination of twist in single spun yarns Untwist/retwist method 1 Scope This International Standard specifies a method for the determination of the
23、 direction of twist in single yarns and the amount of twist, in terms of turns per unit length, by the indirect untwist/retwist method. This International Standard is applicable to single spun yarns. This International Standard is not applicable to: a) open-end spun yarns; b) false twist and self tw
24、ist yarns; c) air-jet yarns; d) yarns that stretch more than 0,5 % when the tension increases from 0,5 cN/tex to 1,0 cN/tex. NOTE Such yarns may be tested under special conditions of tension which are accepted by all parties interested in the test results. e) yarns that are too large to permit their
25、 being placed in the clamps of testing apparatus without crushing or distortion severe enough to affect the test results. The method is designed primarily for yarns in packages, but by the application of special precautions the procedures can be used for yarns taken from fabrics. 2 Normative referen
26、ces The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this
27、International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid
28、 International Standards. ISO 2:1973, Textiles Designation of the direction of twist in yarns and related products ISO 139:1973, Textiles Standard atmospheres for conditioning and testing ISO 2060:1994, Textiles Yarn from packages Determination of linear density (mass per unit length) by the skein m
29、ethod EN 12751, Textiles Sampling of fibres, yarns and fabrics BSISO17202:20021IS:20271 O2002(E) 2 I SO 2002 All irthgs ersedevr3 Terms and definitions For the purposes of this International Standard, the following terms and definitions apply. 3.1 twist number of turns about the axis of a yarn based
30、 on its nominal gauge length before untwisting NOTE Twist should preferably be expressed as turns per metre (turns/m). 3.2 gauge length distance between two effective clamping points of the test specimen mounted in the testing equipment 3.3 initial length length of a test specimen under a specified
31、pretension at the beginning of a test 3.4 moisture equilibrium for testing that state reached when the rate of increase in mass of a sample or specimen in a specified (test) atmosphere does not exceed that prescribed for the material being tested (See ISO 139.) NOTE A textile material is in moisture
32、 equilibrium with the ambient atmosphere when it does not exchange water with this atmosphere; its mass then remains constant as long as the experiment is carried out in an unchanged atmosphere. 3.5 yarn package length or lengths of yarn in a form suitable for use, handling, storing or shipping NOTE
33、 Packages may be comprised of unsupported yarn, such as balls and skeins, or supported yarn, such as cakes, bobbins, cops, cones, pirns, spools, tubes or beams. 3.6 twist factor measure of the spiralling orientation of the fibres in a spun yarn or of the filaments in a filament yarn NOTE It is relat
34、ed to the angle that fibres on the surface of the yarn make with the axis of the yarn and is a measure of the hardness of the resulting yarn due to twist. 4 Principle 4.1 General The untwist/retwist method is an indirect method for determining twist. It involves untwisting a specimen and then retwis
35、ting it in the opposite direction until it has regained its initial length. It is assumed that the number of turns inserted during retwisting is equal to the initial twist of the specimen and that consequently, half the number of turns recorded on the counter represents the twist of the specimen. Th
36、e untwist/retwist method is very sensitive to the pretension used, therefore two methods are proposed: the generally-used method A and a double method B which is less sensitive to inaccuracies in pretension and therefore gives more reliable accurate results. Method B is, however, more time-consuming
37、 than method A and it is therefore recommended mainly for automatic twist testers. BSISO17202:20022IS:20271 O2002(E) I SO 2002 All irthgs ersedevr 34.2 Method A Single method Specimens are tested according to the principle described in 4.1. 4.3 Method B Double method An initial specimen is tested as
38、 described in 4.1. A second specimen is tested by untwisting to a quarter of the turns obtained on the initial specimen, then retwisting back to the initial length to correct for errors caused by pretensioning. 4.4 Comparison of methods The untwist/retwist method, whether A or B, is used for accepta
39、nce testing for economic reasons because it requires less testing time and fewer specimens than the reference direct-counting method. The accuracy of the untwist-retwist method, especially of method B, is good, that is, the results are comparable to those of the direct method, provided appropriate p
40、retension and extension control limits have been utilized. If there is disagreement arising from differences in values reported by the purchaser and the seller when the untwist/retwist method is used for acceptance testing, then the statistical bias, if any, between the laboratory of the purchaser a
41、nd that of the seller should be determined; each comparison shall be based on test specimens randomly drawn from one sample of material of the type being evaluated. The “setting” of twist in some fibres causes excessive contraction when the yarn is retwisted in the reverse direction. Therefore, the
42、number of turns required to bring the specimen back to its original length may be less than the number of turns removed in untwisting. This effect may be partially offset by the use of higher pre-tensioning load; but this increases the danger of stretching the yarn. Little information is available o
43、n the correct tensions to use, either for yarns made from different fibres or with different amounts of twist. The untwist/retwist method can be useful where the objective is to measure variations from an average value. Another possible application is where a large amount of twist testing is require
44、d on yarns of similar type and twist. In this case, preliminary tests comparing the results of the untwist/retwist method with the results of the reference direct method could be used to determine the correct pre-tension. 5 Apparatus 5.1 Twist counter or twist tester, consisting of a pair of clamps,
45、 one of which is rotatable in either direction and positively connected to a revolution counter. The tests are carried out preferably on a motorized twist tester with a speed of 1 000 turns/min 200 turns/min. The position of one clamp (or both clamps) shall be adjustable to accommodate specimens hav
46、ing the length prescribed in 8.1. The tester shall be provided with a variable tensioning device so constructed that a specific load may be applied to the specimen at the beginning and end of the test and removed completely during the intervening untwisting and twisting operations. 6 Standard atmosp
47、here The atmosphere for conditioning and testing shall be as specified in ISO 139. The procedure for conditioning shall follow ISO 139. Preconditioning is not necessary. The amount of twist is not directly affected by changes in relative humidity, but since wide changes in humidity cause changes in
48、length of some materials, all determinations shall be made after conditioning the sample for at least 24 h in the appropriate standard atmosphere. BSISO17202:20023IS:20271 O2002(E) 4 I SO 2002 All irthgs ersedevr7 Sampling Samples shall be taken in one of the following ways: a) according to directio
49、ns, if any, given in the material specification; b) according to EN 12751 if directions on sampling are not included in the material specification; c) according to the method given in annex A, if neither a) nor b) is applicable. Bulk samples shall be taken as directed in A.1. Packages of the laboratory sample shall be taken from the bulk sample as directed in A.2. 8 Test Specimens 8.1 Length The initial length of t
