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1、BRITISH STANDARD BS 3424-8: 1983 Incorporating Amendment No. 1 Testing coated fabrics Part 8: Methods 10A and 10C. Methods for determination of low temperature performance IMPORTANT NOTE. It is recommended that this Part be read in conjunction with the information in Part 0 “Foreword and general inf
2、ormation”. ICS 59.080.40 Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 07:16:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3424-8:1983 This British Standard, having been prepared under the direction of the Fibres, Yarns, Fabrics and Production Standards Committee, was published under the
3、 authority of the Board of BSI and comes into effect on 28 February 1983 BSI 04-1999 The following BSI references relate to the work on this standard: Committee reference FBM/13 Draft for comment 81/36868 DC ISBN 0 580 13023 1 Amendments issued since publication Amd. No.Date of issueComments 9936Jun
4、e 1998Indicated by a sideline in the margin Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 07:16:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3424-8:1983 BSI 04-1999i Contents Page Forewordii 1Scope1 2Method 10A. Determination of cold crack temperature1 3Method 10B. Low temperature bend
5、test2 4Method 10C. Low temperature impact test4 Figure 1 Apparatus for determining cold crack temperature3 Figure 2 Bending jig for coated fabrics5 Figure 3 Bending jig, schematic dimensions6 Figure 4 Illustration of test equipment for low temperature impact test8 Figure 5 Illustration of juxtaposit
6、ion of striker arm and test specimen9 Table 1 Clearance of striking arm and test specimen clamps9 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 07:16:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3424-8:1983 ii BSI 04-1999 Foreword In reviewing m
7、ethod 10 the Committee responsible was concerned to remove the anomalies in test results which had manifested themselves during attempts to apply method 10 to all forms of coated fabrics. At the same time a number of international methods of test were to be considered. Consequently, whilst method 10
8、 (now method 10A) of the last edition has been maintained, it has also been extended in that crack propogation is now more clearly defined. The limitations of the test also have been acknowledged. Text deleted. Method 10B no longer applies. The provisions of method 10C fulfil the requirements of ISO
9、 4646 but additional information has been included concerning test instrument details as it was felt that the information provided by ISO 4646, whilst accurate and unambiguous, was insufficiently detailed and suffered from the criticism that it did not make it explicit that the striking arm needed t
10、o be positively driven if problems associated with the dissipation of momentum of the striking arm were to be avoided. Consequently the details of the test instrument described in ISO 4646 have been supplemented by additional data drawn from BS 903-A25. In so doing, however, the criteria set out in
11、ISO 4646 have been adhered to strictly. Method 10C has been included as a means of assessing low temperature impact performance in those cases where method 10A is found unsuitable due to the specimen configuration during the test. Fabrics coated with rubber or plastics are used in different applicat
12、ions requiring low temperature flexing, and therefore no general relationship between these tests and service performance can be predicted. Other low temperature test methods include BS EN 1876-1:1998 (bending test), which supersedes method 10B, and BS EN 1876-2:1998 (impact test on loop). This Part
13、 of this standard supersedes method 10 of BS 3424:1973. 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 does not of itself confer immunity from lega
14、l obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment ta
15、ble on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 07:16:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3424-8:1983 BSI 04-19991 1 Scope This Part of this British Standard describes two methods of determining the low temperature performance of coated fabrics. NOT
16、EThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Method 10A. Determination of cold crack temperature 2.1 General. The cold crack temperature is not a sharply defined temperature, and it is possible that the range of temperatures over which cracking
17、occurs in some proportion of test specimens varies with different materials. The cold crack temperature varies also with the rate of folding, in that the quicker the folding the higher the temperature at which cracking occurs. The apparatus used in this test is designed to make available sufficient
18、kinetic energy to ensure a flat fold in the test specimen by impact at a velocity of 2 m/s. In addition, the test result is influenced by the criterion of cracking since, in the broadest sense, cracking is anything from a local crack in the surface of the coating not visible to the naked eye, to one
19、 extending across the width of the specimen and down to the fabric; it is essential, therefore, to define the criterion of cracking in such a way as to give the maximum reproducibility of the result. NOTEIt should be noted however that this method is only considered suitable for those materials whic
20、h can, at room temperature, be easily bent into the configuration required by the test without damage to the specimen. For those materials which cannot be bent into the required configuration without damage, it is suggested that the alternative methods in 10C or BS EN 1876-1 may be appropriate. Meth
21、od 10B is no longer appropriate. The method is applicable to coated fabrics having a thickness not greater than approximately 2 mm. 2.2 Principle. Conditioned specimens are exposed in a coolant to decreasing and increasing temperatures around a datum temperature. At each successive change in tempera
22、ture the folded specimens are impacted between a plunger and anvil under defined conditions, after which they are examined visually for cracking. The temperature at which cracking occurs is then determined. 2.3 Apparatus. The apparatus (see Figure 1) comprises of a vertical spring loaded plunger (A)
23、 terminating in a hammer (B) which strikes an anvil (C) on which the looped test specimen (D) is placed. The anvil and the end of the plunger are immersed in methanol cooled to the appropriate temperature. NOTE 1It is permissible to cool the methanol by adding solid carbon dioxide. The lower part (E
24、) of the plunger consists of nylon or other suitable material of low thermal conductivity and the hammer is of brass and 25 mm in diameter. A handle (F) is fitted to the upper end of the plunger. The anvil is of brass and of the same diameter as the hammer. The surfaces of both hammer and anvil are
25、plane and parallel and coincide when in contact. The total mass of the plunger and hammer is 0.45 kg. The compression spring (G) which actuates the plunger has a rate of 2.7 0.1 N/mm and is so fitted that when the hammer is raised from the anvil there is 10 mm free movement before compression of the
26、 spring. A trigger mechanism (H) is provided to hold the plunger against the spring pressure in the position such that the hammer is 35 mm above the anvil. It is important that the plunger moves freely in its housing (J), and that the trigger mechanism does not impede the movement of the plunger whe
27、n released. The plunger spring is in a relaxed state when the apparatus is not in use. The anvil is fixed to the base of the coolant bath (K), which is provided with a mechanical stirrer and a calibrated partial immersion thermometer. The specimen holder (L) comprises of a spring clip (M), and means
28、 are provided for locating it in accordance with 2.7. NOTE 2Care should be exercised to ensure that the spring clip of the specimen holder is positioned so that the specimen is in a horizontal plane and level with the anvil surface, as otherwise additional stress areas may be introduced. 2.4 Prepara
29、tion of test specimens. Twenty specimens 32 mm 6 0.6 mm shall be cut with the longer dimension in the transverse direction of the roll. The strips shall be evenly spaced from the full usable length and width of the sample and not within 50 mm of the selvedge. NOTENormally, approximately 20 specimens
30、 are sufficient for each determination. However, depending upon the type of coated fabric under investigation, the number of specimens required to be tested before the cold crack temperature can be determined, may be less than 20 or, in other cases, greater than 20. (See also 2.8.) 2.5 Conditioning
31、of test specimens. Immediately prior to testing, condition the test specimens in accordance with method 4 (i.e. Part 2 of this standard). 2.6 Time interval between manufacture and testing. For all purposes the minimum time between manufacture and testing shall be at least 16 h. NOTEFor evaluations i
32、ntended to be comparable the tests should, as far as possible, be conducted at the same time interval after manufacture. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 07:16:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3424-8:1983 2 BSI 04-1999 2.7 Procedure. Bend a test specimen into a
33、pear-shaped loop (see Figure 1) approximately 10 mm deep with the face coating outside and insert the ends 2 mm into the clip of the specimen holder. NOTE 1For double face coated fabrics either or both coated surfaces may be evaluated. Use a new specimen for each test. Adjust the coolant bath to the
34、 desired temperature. Place the specimen over the anvil so that the looped end is over the centre and the lower side of the loop touching the anvil. After 15 1 s, release the plunger. Raise the plunger immediately, withdraw the specimen and examine it. For coated fabrics over 70 g/m2 and for coated
35、fabrics with an expanded layer in the coating, increase the immersion time to 30 1 s. The specimen is deemed to have failed if the specimen cracks at the fold of the specimen loop with the crack or cracks extending through to the cloth and over more than half of the specimen width. NOTE 2Persistent
36、cracking elsewhere suggests that the method is not suitable for the material under test. Carry out preliminary tests to locate the approximate cold crack temperature by testing specimens at successively reduced temperatures by intervals of 5 C to 10 C until a specimen fails. Allow the temperature to
37、 rise and test the specimens at 1 C intervals until a specimen passes. The temperature 1 C below this point is the approximate cold crack temperature. Record this approximate cold crack temperature but discard these preliminary results in future calculations. Using fresh test specimens begin the tes
38、t at the approximate cold crack temperature. If the specimen passes, lower the temperature 1 C for the next test. If the specimen fails, raise the temperature 1 C for the next test. Continue testing until at each of two adjacent temperatures at least five results have been obtained such that at the
39、higher temperature there are more passes than fails whilst at the lower temperature there are more fails than passes. Report this higher temperature as the cold crack temperature. 2.8 Compliance testing. For compliance testing purposes where assessment of the coated fabric at a specific temperature
40、is required, test five test specimens at the temperature specified in the product specification. If no more than two test specimens fail at the specified temperature, the coated fabric shall be deemed to pass, unless the product specification stipulates that no failures shall occur. 2.9 Test report.
41、 The test report shall include the following particulars: a) identification of the coated fabric; b) mass per unit area of the coated fabric; c) duration of the exposure period; d) surface(s) tested; e) the cold crack temperature, or, in the case of compliance testing, the temperature at which the t
42、est was conducted and the result, i.e. pass or fail; f) details of any deviations from the standard test procedure. 3 Method 10B. Low temperature bend test 3.1 General. This method specifies a means of determining the ability of fabrics coated with rubber or plastics to resist the effect of low temp
43、erature when subjected to bending at specified temperatures after definite periods of exposure. It is applicable to material with a thickness within the range 0.10 mm to 2.20 mm. For materials of greater thickness than this, modifications to the standard equipment are necessary (see note 3 of 3.6).
44、3.2 Principle. Conditioned specimens are exposed in a cold chamber for a specified time. The specimens are then subjected to a bend test using an appropriate apparatus and examined visually under low magnification. 3.3 Apparatus 3.3.1 Cold chamber, in which the specimens are exposed to low temperatu
45、re and of sufficient size to contain the bending instrument used for testing the specimens and to permit the operation of the instrument without removal from the cold chamber. It is capable of maintaining a uniform atmosphere of cold air or any other suitable gas at specified temperatures to within
46、a tolerance of 1 C. 3.3.2 Bending jig, for bending the specimens, as shown in Figure 2 and Figure 3. Mass tolerance and dimensions are as specified in Figure 3. 3.3.3 Two glass plates, 125 mm 175 mm 3 mm. 3.3.4 Gloves, for handling specimens within the cold cabinet and which are exposed to the same
47、temperature as the test specimens. A second pair of gloves at room temperature shall be available for wearing within the cold gloves as protection for the operator. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 07:16:41 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3424-8:1983 BSI 04-19993
48、3.4 Preparation of test specimens. Three specimens 25 mm 100 mm shall be cut with the longer dimension in the longitudinal direction of the roll. The strips shall be evenly spaced from the full usable length and width of the sample and not within 50 mm of the selvedge. 3.5 Conditioning of test speci
49、mens. Immediately prior to testing, condition the test specimens in accordance with method 4 (i.e. Part 2 of this standard). 3.6 Procedure. Place the three conditioned test specimens between the glass plates. Place the glass plates with the test specimens held in position, the bending jig and the cold gloves in the cold chamber. Expose the specimens for 4 h to the specified test temperature. At the termination of the exposure period and while still in the test chamber, remove the test specimens from between the glass plates, one at a time, (se
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