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1、BRITISH STANDARD BS 5421-2: 1978 Methods of test for Elastomeric threads Part 2: Polyurethane thread (elastane yarn) UDC 678.074:677.55.01:677.556.64 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5421-2:1978 This British Standard, havin
2、g been prepared under the direction of the Rubber Standards Committee, was published under the authority of the Executive Board on 31 August 1978 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference RUC/39 Draft for comment 76/50177 DC ISBN 0 580 10184 3
3、Cooperating organizations The Rubber Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: British Association of Synthetic Rubber Manufacturers British Rubber
4、Manufacturers Association Department of Industry (Chemicals and Textiles) Institution of Production Engineers Malaysian Rubber Producers Research Association* Ministry of Defence Rubber and Plastics Research Association of Great Britain Rubber Growers Association Society of Motor Manufacturers and T
5、raders Limited The organization marked with an asterisk in the above list, together with the following, was directly represented on the committee entrusted with the preparation of this British Standard: British Man-made Fibres Federation Hosiery and Allied Trades Research Association Narrow Fabrics
6、Federation Individual experts Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5421-2:1978 BSI 10-1999i Contents Page Cooperating organizationsInside front cover Forewordiii
7、 1Scope1 2References1 3Method 1: preparation of test specimens1 4Method 2: determination of mass per unit length1 4.1Introduction1 4.2Definition1 4.3Sampling1 4.4Apparatus1 4.5Procedure2 4.6Weighing of test specimens2 4.7Calculation2 4.8Test report2 5Method 3: determination of breaking load, tenacit
8、y and elongation at break2 5.1Principle2 5.2Definitions2 5.3Apparatus2 5.4Sampling2 5.5Procedure2 5.6Calculation3 5.7Test report3 6Method 4: determination of load at predetermined elongation3 6.1Principle3 6.2Definition3 6.3Apparatus3 6.4Sampling3 6.5Procedure3 6.6Calculation3 6.7Test report4 7Metho
9、d 5: determination of stress decay4 7.1Principle4 7.2Definition4 7.3Apparatus4 7.4Sampling4 7.5Procedure4 7.6Calculation4 7.7Test report4 8Method 6: determination of set4 8.1Definition4 8.2Apparatus4 8.3Sampling5 8.4Procedure5 8.5Calculation5 8.6Test report5 9Method 7: resistance to copper staining
10、during laundering5 9.1Introduction5 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5421-2:1978 ii BSI 10-1999 Page 9.2Principle5 9.3Reagents5 9.4Apparatus and materials5 9.5Test pieces5 9.6Preparation of test specimens5 9.7Procedure6 9.8
11、Test report6 10Method 8: resistance to atmospheric fume staining6 10.1 Introduction6 10.2 Principle6 10.3 Reagents6 10.4 Apparatus and materials6 10.5 Test specimens7 10.6 Procedure7 10.7 Test report7 Figure 1 Method 2: apparatus for cutting test pieces8 Figure 2 Method 3: recommended method of posi
12、tioning, tensioning, and clamping a polyurethane thread in the tensile testing machine9 Figure 3 Method 8: suitable apparatus for determining resistance to atmospheric fume staining10 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:04 GMT+00:00
13、2006, Uncontrolled Copy, (c) BSI BS 5421-2:1978 BSI 10-1999iii Foreword This British Standard has been prepared under the direction of the Rubber Standards Committee. Polyurethane thread (elastane yarn) is manufactured elastomeric fibre, in which the fibre-forming substance is a long chain synthetic
14、 polymer which consists of at least 85 % of a segmented polyurethane (see BS 4815). It should be noted that direct comparisons may be made only on new polyurethane threads or those of identical processing histories. In the interpretation of results concerning threads that have been subjected to spoo
15、ling, fabrication, or other processes, the previous history is important, and what is known of this and any relaxation treatments used should be stated. Attention is drawn to Part 1 of this standard which covers methods of test intended primarily for natural or synthetic polyisoprene rubber thread.
16、For users of this standard who may not be familiar with the International System of units (SI) as applied in these methods, the following explanations may be helpful. a) newton (N) The newton (N) is the unit of force. One newton (1 N) is the force which, when applied to a body having a mass of one k
17、ilogram (1 kg), imparts to it an acceleration of one metre per second squared (1 m/s2). b) tex Tex is the unit of linear density used in the textile industry. A fibre which has a mass of M grams per 1 000 metres of length is said to have a linear density of M tex. 1 tex = 106 kg/m. c) centinewton pe
18、r tex (cN/tex) The centinewton per tex (cN/tex) is the unit used to quantify all expressions of force per linear density (breaking load and pretension). For further explanation, reference should be made to BS 3763 and to PD 5686. The methods in this Part of BS 5421 have been submitted for considerat
19、ion to Technical Committee ISO/TC 45 Rubber and Rubber Products, of the International Organization for Standardization (ISO). A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Complianc
20、e with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have ha
21、d amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:04 GMT+00:00 2006, Unco
22、ntrolled Copy, (c) BSI BS 5421-2:1978 BSI 10-19991 1 Scope This Part of BS 5421 describes eight methods of test for polyurethane thread (elastane yarn): 2 References The titles of the publications referred to in this standard are listed on the inside back cover. 3 Method 1: preparation of test speci
23、mens The samples or test specimens shall be kept in a relaxed state in the dark in an atmosphere with a temperature of 20 2 C and a relative humidity of 65 5 %, for not less than 16 h before test. The tests shall be carried out in the same atmosphere. The test specimens selected shall be clean, dry,
24、 and free from any visible defects. Samples or test specimens that are to be exposed to ageing or wet treatment shall not be allowed to come into contact with copper or manganese or with their alloys or compounds during preparation or testing. When the yarn is taken from a package, care should be ex
25、ercised to see that the thread is not elongated. It is desirable that the sample for use in method 3 (determination of breaking load, tenacity and elongation at break) should be cut from pieces of yarn on which the determination of mass per unit length (method 2) has been made. 4 Method 2: determina
26、tion of mass per unit length 4.1 Introduction. This method is intended for threads in the “as received” condition, but may be used for treated threads provided that the treatment is specified. The method does not cover finish removal procedures to determine the mass per unit length of “finish free”
27、threads. Owing to the complexity of the methods existing for accurate determination of thread finish, e.g. infra-red analysis, it is deemed best that information with regard to finish content should be supplied by the thread manufacturer. The value of mass per unit length, determined by the followin
28、g method, may be used in conjunction with other physical tests provided that the samples or test specimens have not been heated or subjected to other forms of handling that might change their mass per unit length. 4.2 Definition. For the purposes of this method the following definition applies. mass
29、 per unit length the quotient obtained by dividing the mass of the thread by its length, the preferred units of measurement being in grams per 1 000 metres (tex) 4.3 Sampling. Cut a minimum of five specimens to approximately 1.5 m each in length. If these samples are taken from bobbins, or from any
30、other form of presentation in which the thread is under tension, allow them to relax for at least 48 h under the conditions specified in clause 3. Samples taken from forms of presentation where no tension is applied to the thread shall be conditioned as specified in clause 3. 4.4 Apparatus (see Figu
31、re 1). The following apparatus is required. 4.4.1 A rectangular vertical frame 4.4.2 Two metallic plates, mounted at the upper and lower ends of the frame; the inside edges shall be parallel and sharp, and the distance between them shall be 1 000 1 mm. 4.4.3 Two cutting devices, the fixed blades of
32、which consist of the inside edges of the metallic plate. 4.4.4 Two external clamps, of a spring loaded type. method 1 Preparation of test specimens; method 2 Determination of mass per unit length; method 3 Determination of breaking load, tenacity and elongation at break; method 4 Determination of lo
33、ad at predetermined elongation; method 5 Determination of stress decay; method 6 Determination of set; method 7 Resistance to copper staining during laundering; method 8 Resistance to atmospheric fume staining. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:04 GMT+00:00 2006, Uncontrol
34、led Copy, (c) BSI BS 5421-2:1978 2 BSI 10-1999 4.5 Procedure. Take the specified number of samples of thread, and cut and condition them as specified in 4.3. Suspend each conditioned thread from the upper clamp. When it has settled in the vertical position without stretch, fix it by means of the low
35、er clamp. Then cut the thread to 1 000 1 mm in length with the two cutting devices, using the lower one first. 4.6 Weighing of test specimens. Weigh each test specimen separately to three significant figures. 4.7 Calculation. Calculate the average mass of the test specimens. The average mass per uni
36、t length in tex is equal to the average mass of the 1 000 mm lengths in mg. 4.8 Test report. The test report shall include the following information: a) identification of the thread; b) number of specimens tested; c) average mass per unit length (in tex); d) a reference to this British Standard, i.e
37、. BS 5421-2, method 2. 5 Method 3: determination of breaking load, tenacity and elongation at break 5.1 Principle. A thread specimen is placed in the clamps of a tensile testing machine and is stretched until broken; the breaking force and elongation are then observed. 5.2 Definitions. For the purpo
38、ses of this method the following definitions apply. 5.2.1 breaking load the maximum force which a test specimen can support during a test of loading to break under defined conditions. The preferred units for breaking load are the centinewton (cN) (for yarns and fibres) and the decanewton (daN) (for
39、cords) 5.2.2 tenacity the breaking load, expressed as force per mass per unit length of the unstrained specimen, i.e. cN/tex 5.2.3 elongation the increase in length of a stretched specimen, expressed as a percentage of the original length 5.2.4 elongation at break the elongation corresponding to the
40、 breaking load 5.3 Apparatus. The following apparatus is required. 5.3.1 Tensile testing machine of the constant rate of extension type, with an autographic recorder. The tensile testing machine shall be of the low inertia type, in accordance with BS 5214-1, having an accuracy of force measurement o
41、f grade B and an extensometer accuracy of grade D. The force capacity shall be such that the thread ruptures within 15 % to 85 % of the selected scale range. A machine with a capacity ranging from 10 cN to 2 000 cN is usually adequate. 5.3.2 Tensioning weight to provide pretensioning of the thread a
42、t 0.003 0.001 cN/tex. 5.3.3 Clamping assembly. Line contact clamps, one jaw having a flat steel face (nominally 25 mm 25 mm) and the other jaw having a convex 3 mm radius steel face (nominally 25 mm 6 mm). 5.3.4 Rubber tubing of 1.6 mm nominal bore, 0.8 mm wall thickness and rubber hardness less tha
43、n 45 IRHD. 5.3.5 Needle threader or other means for passing the thread through the rubber tubing. 5.4 Sampling. A minimum of five specimens (see clause 3) shall be tested. 5.5 Procedure. Take representative test specimens of known mass per unit length (see clause 4) and cut each one to approximately
44、 125 mm in length. Adjust the tensile testing machine as follows. Gauge length: 50 0.5 mm Cross head speed: 500 mm/min Chart speed: 500 mm/min Locate the clamps so that the convex surfaces are in a horizontal plane. (See Figure 2.) Cut two pieces of rubber tubing each approximately 12.5 mm long. Thr
45、ead the test specimen through one piece of tubing using the needle threader so that approximately 25 mm of thread extends beyond one end of the tubing. Grasp the threaded tubing with forceps and place it in the central part of the top clamp so that approximately 6 mm of tubing and 90 mm of the threa
46、d are below the contact point. Close the top clamp. Thread the free end through the second piece of tubing and place the tubing in the lower clamp directly beneath the upper tubing, with approximately 6 mm of tubing above the clamp. Attach a tensioning weight, equivalent to 0.003 0.001 cN/tex, to th
47、e thread below the lower clamp. Close the lower clamp and remove the tensioning weight. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5421-2:1978 BSI 10-19993 Select the range of the tensile testing machine so that the estimated breakin
48、g force required to rupture the thread falls between 15 % and 85 % of the full scale deflection. Start the machine, observe and record the breaking force and elongation. If a specimen breaks within the rubber tubing disregard the result and test another specimen. (During the testing of multifilament
49、 thread, the first filament break should be recorded.) 5.6 Calculation 5.6.1 Breaking load. Read the breaking force directly from the chart. 5.6.2 Tenacity. Calculate the average tenacity (in cN/tex) from the following expression: 5.6.3 Elongation at break. Read the elongation at maximum force from the force elongation chart. Calculate the percent elongation on the basis of the nominal gauge length. 5.7 Test report. The test report shall include the following information: a) the make and model of testing machine used; b) the number of specimens