BS 3424-16-1995 Testing coated fabrics Method 18 Determination of air permeability《涂覆织物测试 第16部分 透气性测定》.pdf

1、BRITISH STANDARD BS3424-16: 1995 Testing coated fabrics Part 16: Method18. Determination of air permeability IMPORTANT NOTE. It is recommended that this Part be read in conjunction with the information in Part 0: Foreword and general introduction.BS3424-16:1995 This British Standard, having been pre

2、pared under the direction of the Sector Board for Materials and Chemicals, was published under the authority of the Standards Board and comes into effect on 15 December 1995 BSI 03-1999 The following BSI references relate to the work on this standard: Committee reference PRI/78 Draft for comment94/3

3、42269DC ISBN 0 580 24507 1 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee PRI/78, Coated fabrics, upon which the following bodies were represented: British Apparel and Textile Confederation British Plastics Federation Br

4、itish Railways Board British Rubber Manufacturers Association Ltd. British Textile Technology Group Department of Health Department of the Environment (Building Research Establishment) Furniture Industry Research Association Home Office Industrial Safety (Protective Equipment) Manufacturers Associat

5、ion Made-Up Textiles Association RAPRA Technology Ltd. SATRA Footwear Technology Centre Society of Motor Manufacturers and Traders Limited The following body was also represented in the drafting of the standard, through subcommittees and panels: Ministry of Defence Amendments issued since publicatio

6、n Amd. No. Date CommentsBS3424-16:1995 BSI 03-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Normative references 1 3 Principle 1 4 Apparatus 1 5 Selection of test specimens 1 6 Preparation of test specimens 1 7 Atmosphere 1 8 Procedure 1 9 Calculation and exp

7、ression of results 1 10 Test report 2 Annex A (informative) Suitable test apparatus 3 Figure A.1Illustration of suitable test apparatus arrangements 3 List of references Inside back coverBS3424-16:1995 ii BSI 03-1999 Foreword This British Standard has been prepared by Technical Committee PRI/78, Coa

8、ted fabrics. Air permeability is an important factor in the performance of products such as filters, clothing, tentage, sails, parachutes, building structures and acoustical suppressers. The level of permeability may be required to be relatively high for some applications or extremely low for others

9、. For some applications such as gaskets, protective equipment and airbags, the coated fabric may need to be resistant to the passage of gases even at the molecular level. In these latter instances, the methods of test in BS903-A30 or BS2782:Method 821 A are more appropriate. A British Standard does

10、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 legal obligations. Summary of pages This document comprises a front cover, an inside

11、 front cover, pages i and ii, pages 1 to 4, 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 table on the inside front cover.BS3424-16:1995 BSI 03-1999 1 1 Scope This Part of B

12、S3424 describes a method for determining the air permeability of coated fabrics. Itis suitable for measuring the air permeability of perforated coated fabrics used for filters, coverings and acoustical absorbers such as car headlining where the air permeability is not less than8mm/s at98Pa. 2 Normat

13、ive references This British Standard incorporates, by reference, provisions from specific editions of other publications. These normative references are cited at the appropriate points in the text and the publications are listed on the inside back cover. Subsequent amendments to, or revisions of, an

14、y of these publications apply to this British Standard only when incorporated in it by updating or revision. For undated references, the latest edition of the cited publication applies, together with any amendments. 3 Principle The rate of air flow through a known area of coated fabric is adjusted s

15、o that there is a known pressure drop across the fabric. 4 Apparatus 4.1 A rigidly mounted circular specimen holder, having an orifice5cm 2 ,20cm 2 ,50cm 2or100cm 2 , (i.e25.23mm 0.05mm,50.05mm 0.05mm, 79.79mm 0.05mm or112.84mm 0.05mm diameter). 4.2 Means for clamping the test specimen, securely and

16、 without distortion in the circular specimen holder and means for preventing leakage of air from the edges of the test specimen. NOTELeakages may be measured separately and taken into account in calculating results. 4.3 A calibrated pressure gauge or manometer, accurate to within 2% of the recorded

17、or indicated pressure. 4.4 A suction pump, capable of drawing a steady flow of air through the test specimen. Means shall be provided for adjusting the suction rate so that the pressure differential across the test specimen is maintained at a constant of50Pa,100Pa,200Pa,500Pa or1kPa. 4.5 Calibrated

18、flow meters or volumetric counters, to indicate the velocity and volume of air passing through the test specimen. NOTE 1Measurement on the inlet and outlet sides of the test specimen are advisable. NOTE 2Illustrations of suitable arrangements are given in informative Annex A. 5 Selection of test spe

19、cimens Select seven test specimens, each of a size appropriate to the apparatus being used. NOTEThis usually requires a test specimen to be not less than25mm greater in diameter than the orifice of the specimen holder (see4.1). If the coefficient of variation of individual observations on similar ma

20、terials is known, the number of tests conducted may be varied according to the relationship. n=0.154 V 2 where 6 Preparation of test specimens Pre-condition and condition each test specimen in accordance with Part2 of BS3424, ensuring that each test piece is kept flat, unfolded and undisturbed, for

21、not less than3h. 7 Atmosphere Ensure that the temperature, relative humidity and barometric pressure of the air surrounding the test apparatus and being drawn into the test circuit is maintained to within5% of the required conditions between the beginning and end of the test. Unless otherwise specif

22、ied these conditions should be those specified in BS3424-2. 8 Procedure NOTEAdvice on checking and calibrating the apparatus is given in Annex A. Mount the test specimen in the circular specimen holder(4.1), (coated surface to low pressure side if single faced) with sufficient tension to eliminate w

23、rinkles or creases but without distorting the fabric construction or coating. Avoid selvedges. Start the suction pump(4.4) and adjust the rate of flow until the required pressure differential (see4.4) is obtained. Record the air flow rate in litres per minute (see4.5). Maintain the pressure differen

24、tial for a further1min and again record the air flow rate in litres per minute. NOTEFor apparel fabrics a pressure drop of not less than200Pa is recommended but for most coated fabric applications the pressure differential will need to be at least500Pa. 9 Calculation and expression of results 9.1 Me

25、an air flow rate and CV% Calculate the arithmetic mean of the air flow rates recorded in clause8 and determine the coefficient of variation to the nearest0.1% at the95% confidence level using BS5324 or BS2846-1. n is the number of tests conducted; V is the coefficient of variation of test results.BS

26、3424-16:1995 2 BSI 03-1999 9.2 Air permeability Calculate the air permeability (R) inmm/s as follows: where Report the results to the nearest2% of R. NOTENo recent interlaboratory tests have been conducted using this method. Statements in ASTMD737 would suggest that the variance for air permeability

27、 of coated fabrics expressed as a coefficient of variation, when the test is conducted in a single laboratory by the same operator, is typically between3% to6% and that if results differ by more than a factor of4.7as a critical difference using7 test results or by a factor of3.31 using14 test result

28、s, the difference is statistically significant at the95% probability level. 10 Test report The test report shall include the following particulars: a) the description of the coated fabric tested and reference to this method of test; b) the mean air permeability; c) the number of test specimens teste

29、d; d) if the coated fabric is a single faced fabric, which side of the coated fabric was exposed to the incoming air; e) confirmation of the air temperature, relative humidity and barometric pressure throughout the test; f) the pressure differential applied across the test specimen; g) any deviation

30、s from the standard test procedure. r is arithmetic mean of the air flow rate in L/min determined at9.1; A area of orifice of test assembly (see4.1) incm 2 . R r A -167 =BS3424-16:1995 BSI 03-1999 3 Annex A (informative) Suitable test apparatus A.1 Advice on checking and calibrating the apparatus It

31、 is advisable to verify the calibration and proper functioning of the apparatus weekly, if in daily use, and prior to testing if used infrequently, and after the instrument has been moved or repaired. The calibration of the instrument should be checked periodically against a primary reference standa

32、rd and at intervals of not greater than12months. The accuracy of the pressure gauge, temperature recording devices, flow meters and psychrometers should be verified periodically and at intervals not greater than12months. Figure A.1 Illustration of suitable test apparatus4 blankBS3424-16:1995 BSI 03-

33、1999 List of references (see clause2) Normative references BSI publications BS903, Physical testing of rubber. BS903-A30:1975, Determination of the permeability of rubber to gases (constant pressure method). BS2782, Methods of testing plastics. BS2782-8, Other properties. BS 2782:Method821A:1979, De

34、termination of the gas transmission lates of films and thin sheets under atmospheric pressure (manometric method). BS2846, Guide to statistical interpretation of data. BS2846-1:1991, Routine analysis of quantitative data. BS5324:1976, Guide to application of statistics to rubber testing. Other publi

35、cations ASTMD.737-75, Standard test method for iar permeability of textile fabrics 1) . 1) published by the American Society for Testing and MaterialsASTM1916 Race St Philadelphia, PA19103USA.BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |

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