1、BRITISH STANDARD BS 5421-2: 1978 Methods of test for Elastomeric threads Part 2: Polyurethane thread (elastane yarn) UDC 678.074:677.55.01:677.556.64BS5421-2:1978 This British Standard, having been prepared under the directionof the Rubber StandardsCommittee, was published under the authority ofthe
2、Executive Board on 31August1978 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 Cooperating organizations The Rubber Standards Committee, under whose direction this British Standard was prepared
3、, consists of representatives from the following Government departments and scientific and industrial organizations: British Association of Synthetic Rubber Manufacturers British Rubber Manufacturers Association Department of Industry (Chemicals and Textiles) Institution of Production Engineers Mala
4、ysian Rubber Producers Research Association* Ministry of Defence Rubber and Plastics Research Association of Great Britain Rubber Growers Association Society of Motor Manufacturers and Traders Limited The organization marked with an asterisk in the above list, together with the following, was direct
5、ly 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 Federation Individual experts Amendments issued since publication Amd. No. Date of issue CommentsBS5421-2:1978 BSI
6、 10-1999 i Contents Page Cooperating organizations Inside front cover Foreword iii 1 Scope 1 2 References 1 3 Method 1: preparation of test specimens 1 4 Method 2: determination of mass per unit length 1 4.1 Introduction 1 4.2 Definition 1 4.3 Sampling 1 4.4 Apparatus 1 4.5 Procedure 2 4.6 Weighing
7、of test specimens 2 4.7 Calculation 2 4.8 Test report 2 5 Method 3: determination of breaking load, tenacity and elongation at break 2 5.1 Principle 2 5.2 Definitions 2 5.3 Apparatus 2 5.4 Sampling 2 5.5 Procedure 2 5.6 Calculation 3 5.7 Test report 3 6 Method 4: determination of load at predetermin
8、ed elongation 3 6.1 Principle 3 6.2 Definition 3 6.3 Apparatus 3 6.4 Sampling 3 6.5 Procedure 3 6.6 Calculation 3 6.7 Test report 4 7 Method 5: determination of stress decay 4 7.1 Principle 4 7.2 Definition 4 7.3 Apparatus 4 7.4 Sampling 4 7.5 Procedure 4 7.6 Calculation 4 7.7 Test report 4 8 Method
9、 6: determination of set 4 8.1 Definition 4 8.2 Apparatus 4 8.3 Sampling 5 8.4 Procedure 5 8.5 Calculation 5 8.6 Test report 5 9 Method 7: resistance to copper staining during laundering 5 9.1 Introduction 5BS5421-2:1978 ii BSI 10-1999 Page 9.2 Principle 5 9.3 Reagents 5 9.4 Apparatus and materials
10、5 9.5 Test pieces 5 9.6 Preparation of test specimens 5 9.7 Procedure 6 9.8 Test report 6 10 Method 8: resistance to atmospheric fume staining 6 10.1 Introduction 6 10.2 Principle 6 10.3 Reagents 6 10.4 Apparatus and materials 6 10.5 Test specimens 7 10.6 Procedure 7 10.7 Test report 7 Figure 1 Meth
11、od 2: apparatus for cutting test pieces 8 Figure 2 Method 3: recommended method of positioning, tensioning, and clamping a polyurethane thread in the tensile testing machine 9 Figure 3 Method 8: suitable apparatus for determining resistance to atmospheric fume staining 10 Publications referred to In
12、side back coverBS5421-2:1978 BSI 10-1999 iii 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 polymer which con
13、sists of at least85% of a segmented polyurethane (see BS4815). 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 spooling, fabrication, or
14、 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 Part1 of this standard which covers methods of test intended primarily for natural or synthetic polyisoprene rubber thread. For users of this stan
15、dard 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 (1N) is the force which, when applied to a body having a mass of one kilogram (1kg), imparts
16、to it an acceleration of one metre per second squared (1m/s 2 ). b) tex Tex is the unit of linear density used in the textile industry. A fibre which has a mass of M grams per1 000metres of length is said to have a linear density of M tex. 1 tex = 10 6kg/m. c) centinewton per tex (cN/tex) The centin
17、ewton 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 BS3763 and to PD5686. The methods in this Part of BS5421 have been submitted for consideration to Technical Committee I
18、SO/TC45 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. Compliance with a British Standard doe
19、s not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi toiv, pages1to10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This wi
20、ll be indicated in the amendment table on the inside front cover.iv blankBS5421-2:1978 BSI 10-1999 1 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
21、 back cover. 3 Method 1: preparation of test specimens The samples or test specimens shall be kept in a relaxed state in the dark in an atmosphere with a temperature of20 2 C and a relative humidity of65 5%, for not less than16h before test. The tests shall be carried out in the same atmosphere. The
22、 test specimens selected shall be clean, dry, 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 ya
23、rn is taken from a package, care should be exercised to see that the thread is not elongated. It is desirable that the sample for use in method3 (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 (me
24、thod2) has been made. 4 Method 2: determination 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
25、 the mass per unit length of “finish free” 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
26、per unit length, determined by the following 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 me
27、thod the following definition applies. mass per unit length the quotient obtained by dividing the mass of the thread by its length, the preferred units of measurement being in grams per1 000metres (tex) 4.3 Sampling. Cut a minimum of five specimens to approximately1.5m each in length. If these sampl
28、es are taken from bobbins, or from any other form of presentation in which the thread is under tension, allow them to relax for at least48h under the conditions specified in clause3. Samples taken from forms of presentation where no tension is applied to the thread shall be conditioned as specified
29、in clause3. 4.4 Apparatus (see Figure 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 be1 000 1mm. 4.4.3 Two cutt
30、ing devices, the fixed blades of 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 br
31、eak; method 4 Determination of load 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.BS5421-2:1978 2 BSI 10-1999 4.5 Procedure. Take the speci
32、fied number of samples of thread, and cut and condition them as specified in4.3. Suspend each conditioned thread from the upper clamp. When it has settled in the vertical position without stretch, fix it by means of the lower clamp. Then cut the thread to1000 1mm in length with the two cutting devic
33、es, 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 unit length in tex is equal to the average mass of the1000mm lengths in mg. 4.8 Tes
34、t 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. BS5421-2, method 2. 5 Method 3: determination of breaking load, tenacity and elon
35、gation 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 purposes of this method the following definitions apply. 5.2.1 breaking load the maximum
36、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 cords) 5.2.2 tenacity the breaking load, expressed as force per mass per unit length
37、 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 breaking load 5.3 Apparatus. The following apparatus is required. 5.3.1 Tensile tes
38、ting 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 BS5214-1, having an accuracy of force measurement of grade B and an extensometer accuracy of grade D. The force capacity shall be such t
39、hat the thread ruptures within15% to85% of the selected scale range. A machine with a capacity ranging from10cN to2000cN is usually adequate. 5.3.2 Tensioning weight to provide pretensioning of the thread at0.003 0.001 cN/tex. 5.3.3 Clamping assembly. Line contact clamps, one jaw having a flat steel
40、 face (nominally25mm 25mm) and the other jaw having a convex3mm radius steel face (nominally25mm 6mm). 5.3.4 Rubber tubing of 1.6mm nominal bore,0.8mm wall thickness and rubber hardness less than45IRHD. 5.3.5 Needle threader or other means for passing the thread through the rubber tubing. 5.4 Sampli
41、ng. A minimum of five specimens (see clause3) shall be tested. 5.5 Procedure. Take representative test specimens of known mass per unit length (see clause4) and cut each one to approximately125mm in length. Adjust the tensile testing machine as follows. Gauge length: 50 0.5 mm Cross head speed: 500
42、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 approximately12.5mm long. Thread the test specimen through one piece of tubing using the needle threader so that approximately25mm of thread ex
43、tends 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 approximately6mm of tubing and90mmof the thread are below the contact point. Close the top clamp. Thread the free end through the second piece of tubing and place the
44、tubing in the lower clamp directly beneath the upper tubing, with approximately6mm of tubing above the clamp. Attach a tensioning weight, equivalent to0.003 0.001cN/tex, to the thread below the lower clamp. Close the lower clamp and remove the tensioning weight.BS5421-2:1978 BSI 10-1999 3 Select the
45、 range of the tensile testing machine so that the estimated breaking force required to rupture the thread falls between15% and85% 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
46、and test another specimen. (During the testing of multifilament 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
47、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
48、 of specimens tested; c) the individual values and the average values for the breaking force, tenacity and elongation at break; d) a reference to this British Standard, i.e. BS5421-2, method3. 6 Method 4: determination of load at predetermined elongation 6.1 Principle. The thread is cycled six times
49、 to an elongation greater than that at which readings will be taken and the force/elongation curve is recorded on the sixth cycle. 6.2 Definition. For the purposes of this method the following definition applies. load at a predetermined elongation the tensile force exerted by the thread at a specified elongation which is measured on extension (stretch resistance) and retraction (recovery power). The results are expressed in centinewtons for a given mass per unit length 6.3 Apparatus. The following apparatus is required. 6.3.1 Tensile testing machi
