1、BRITISH STANDARD BS7406:1991 ISO9932:1990 Methods for Determination of water vapour transmission rate of sheet materials (paper and board) by dynamic sweep and static gas methodsBS7406:1991 This BritishStandard, having been prepared under the directionof the Paper and PrintingStandards Policy Commit
2、tee, was published underthe authority of the BoardofBSI and comes intoeffecton 31 January1991 BSI12-1999 The following BSI references relate to the work on this standard: Committee reference PAM/11 Draft for comment89/39832DC ISBN 0 580 19317 9 Committees responsible for this BritishStandard The pre
3、paration of this BritishStandard was entrusted by the Paper and Printing Standards Policy Committee (PAM/-) to Technical Committee PAM/11, upon which the following bodies were represented: British Fibreboard Packaging Association British Paper and Board Industry Federation (PIF) British Printing Ind
4、ustries Federation British Telecommunications plc Envelope Makers and Manufacturing Stationers Association Her Majestys Stationery Office Man-made Fibres Producers Committee Ministry of Defence Paper Sack Development Association Ltd. PIRA (the Research Association for the Paper and Board, Printing a
5、nd Packaging Industries) Post Office Society of British Printing Ink Manufacturers University of Manchester Institute of Science and Technology Amendments issued since publication Amd. No. Date CommentsBS7406:1991 BSI 12-1999 i Contents Page Committees responsible Inside front cover National forewor
6、d ii 1 Scope 1 2 Normative references 1 3 Definitions 1 4 Method A: Dynamic sweep gas method 1 5 Method B: Static gas method 2 6 Sampling 2 7 Preparation of test pieces 2 8 Procedure 2 9 Expression of results 3 10 Precision 3 11 Test report 3 Annex A (normative) Saturated saline solutions 6 Annex B
7、(normative) Calibration 6 Annex C (informative) Comparison of dynamic method with gravimetric method 7 Figure 1 Schematic diagram of dynamic system 4 Figure 2 Schematic diagram of static system 5 Figure C.1 Dynamic method compared with gravimetric method 7 Table A.1 6 Publication(s) referred to Insi
8、de back coverBS7406:1991 ii BSI 12-1999 National foreword This BritishStandard has been prepared under the direction of the Paper and Printing Standards Policy Committee. It is identical with ISO9932:1990 “Paperand board Determination of water vapour transmission rate of sheet materials Dynamic swee
9、p and static gas methods”, published by the International Organization for Standardization (ISO). The Technical Committee has reviewed the provisions of ISO2528:1974, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A related
10、 BritishStandard to ISO2528:1974 is BS3177:1959 “Method for determining the permeability to water vapour of flexible sheet materials used for packaging”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their co
11、rrect application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International Standard Corresponding BritishStandard ISO186:1985 BS3430:1986 Method for sampling to determine the average quality of paper and board (Identical) ISO187:19
12、77 BS3431:1973 Method for the conditioning of paper and board for testing (Technically equivalent) Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to8, an inside back cover and a back cover. This standard has been updated (see copyright date) and m
13、ay have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS7406:1991 BSI 12-1999 1 1 Scope This International Standard describes general test methods for determining the water vapour transmission rate of sheet materials by means of a dynamic gas me
14、thod or a static gas method. Depending on the method and specific apparatus employed, materials up to38mm thick and with water vapour transmission rates in the range0,05g/(m 2 d) to65g/(m 2 d) can be tested. The basis of the function of the instrumental techniques is briefly described. Advice on cal
15、ibration is given in Annex B. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions or this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parti
16、es to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions or the standards indicated below. Members of IEC and ISO maintain registers or currently valid International Standards. ISO186:1985, Paper and board Sampling to de
17、termine average quality. ISO187:1977, Paper and board Conditioning of samples. ISO2528:1974, Sheet materials Determination of water vapour transmission rate Dish method. 3 Definitions For the purposes of this International Standard, the following definitions apply. 3.1 water vapour transmission rate
18、 the mass of water vapour transmitted through unit area in unit time under specified conditions of temperature and humidity, it is expressed in grams per square metre per24hg/(m 2 d) 3.2 dry side that side or the test cell which is exposed to low humidity 3.3 wet side that side of the test cell whic
19、h is exposed to high humidity 4 Method A: Dynamic sweep gas method 4.1 Principle The test piece is mounted between two chambers. one at a known relative humidity and the other swept by a dry gas. The amount of water vapour picked up by the dry gas stream is detected by an electrical sensor and conve
20、rted to a reading which directly, or after calculation, is a measure of the rate of water vapour transmission through the test piece. 4.2 Apparatus 1) 4.2.1 Test cell, designed to clamp a test piece having a defined area, between two chambers, one swept by a dry gas (the dry side) and the other cont
21、aining an atmosphere of high relative humidity (the wet side)(seeFigure 1). 4.2.2 Clamping arrangements, to allow rapid insertion and removal of the test piece, equipped with suitable gaskets against which the test piece is sealed by the clamping force. 4.2.3 Provision for maintaining humidity on th
22、e wet side at the desired level. The required level of relative humidity may be obtained with saturated saline solutions containing a solid phase as described in Annex A or by distilled water if100% relative humidity is required. 4.2.4 Inert dry gas (as required by the specific apparatus to be used)
23、, for purging on the dry side. NOTE 1The gas is normally desiccated air or dry nitrogen. 4.2.5 Sensor, with rapid response and high sensitivity capable of detecting levels in the moisture content of the sweep gas equivalent to0,05% relative humidity or less. The sensor may take a number of forms: an
24、 electrical resistance element, an electrolytic cell, or an infra-red detector. 4.2.6 Means to convert the output from the sensor into a signal that can be used to calculate the amount of moisture passing through the test piece being tested in unit time. 4.2.7 Means of maintaining the test chamber a
25、nd the sweep gas and the sensor at the required temperature. NOTE 2The normal test temperature is either23 C 1 C or38 C 1 C, but other temperatures may be used. 4.2.8 Specimen of stated water vapour transmission rate supplied by the instrument manufacturer for standardization of the test cell. 1) Th
26、e EPS digital WVTR meter and the Permatron W-series are examples of suitable instruments available commercially. Thisinformation is given for the convenience of users of this International Standard and does not constitute an endorsement by ISO of these instruments.BS7406:1991 2 BSI 12-1999 5 Method
27、B: Static gas method 5.1 Principle The test piece is mounted in a cell containing an electrolytic element and the cell placed in a humidity cabinet at the required temperature and relative humidity. The water vapour penetrating the cell is electrolyzed and consequently the relative humidity within t
28、he cell remains very low(1%). After equilibrium, the electric current is a direct measure of the rate of electrolysis (according to Faradays law of electrolysis) and the water vapour transmission rate. 5.2 Apparatus 2) 5.2.1 Control box, containing a) an electric power supply; b) a microammeter, gra
29、duated directly in grams per square metre per24hg/(m 2 d); c) selector and range switches; d) connection points for cells and, if desired, a recorder. 5.2.2 Humidity cabinet, for storing the cells at the required conditions and having a fan for air circulation and small openings for entry of the plu
30、gs and cables of the cells. The required level of relative humidity may be obtained as prescribed in4.2.3. 5.2.3 Stainless steel test cells, designed to clamp a defined area of a test piece and containing an electrolytic element which can be connected to the control box by means of a cable and plug.
31、 5.2.4 Electrolytic element, consisting of two platinum wires wound at constant pitch round an inert former (glass and polytetrafluorethylene are suitable materials). A film of phosphorus pentoxide is deposited over the surface of the wires and former. 5.2.5 Means of drilling holes in test pieces. 5
32、.2.6 Specimen of stated water vapour transmission rate. 6 Sampling Select samples in accordance with ISO186. 7 Preparation of test pieces Test pieces shall be representative of the sample and shall take into account, where appropriate, variations within and between sheets and batches. The test area
33、shall be free from faults likely to affect the determination. The faces shall be designated one and two respectively. Where the two faces of the material can be distinguished, face one shall denote the face exposed to the wet side in service. Carefully, in order to avoid damage to the test area, cut
34、10 test pieces to the required size and drill holes as necessary for the test cell being used. Composite materials may have a core of permeable material which can provide a secondary path for moisture permeation if the edges are left exposed. In this case apply aluminium foil tape to the edges of su
35、ch test pieces. The foil tape shall cover the edges and overlap the face by at least10mm. The foil tape shall be of the self-adhesive type, using dead sort tempered foil at least404m thick. Thick test pieces of homogenous construction may also allow moisture permeation through the edges and should a
36、lso be treated as above. NOTE 3No definitive statement can be given about the thickness at which sealing the edges becomes necessary, but as a general rule this should not be necessary for thicknesses less than5mm. 8 Procedure The precise method to be used shall be obtained from the manufacturers op
37、eration manual. Thegeneral procedure is as follows. 8.1 Method A Fill the lower part of the test cell with water or the appropriate saturated saline solution containing a solid phase in order to obtain the required humidity and clamp the test piece in the cell with face one towards the wet side of t
38、he cell. Set the apparatus to the required temperature. Operate the apparatus in accordance with the manufacturers instructions to obtain a reading, ensuring that a steady state has been reached. Record this reading and repeat the procedure for the remaining test pieces so that five readings are obt
39、ained with face one towards the wet side and five readings with face two towards the wet side. 8.2 Method B Clamp the test piece in the cell with face one towards the wet side. Place the cell in the humidity cabinet at the required temperature and relative humidity. Record the rate of electrolysis o
40、f the water vapour passing into the cell as indicated by the microammeter until a steady state has been reached. Record the reading and repeat the procedure so that five readings are obtained with face one towards the wet side and five readings with face two towards the wet side. 2) The TNO/Pira WVT
41、R meter is an example of a suitable instrument available commercially. This information is given for the convenience of users of this International Standard and does not constitute an endorsement by ISO of this instrument.BS7406:1991 BSI 12-1999 3 8.3 Barrier material having one face of uncoated pap
42、er Where one face of a barrier material consists of uncoated paper, and this face is towards the dry side, difficulties can be expected. All water must be removed from the paper by the dry gas before a constant water vapour transmission rate is indicated on the meter or recorder. NOTE 4The pre-condi
43、tioning can last several days and care should be taken to ensure that a true steady state has been reached. It is recommended that the test be carried out only with the paper towards the wet side. Where a water vapour transmission rate determination yields a value grossly different from comparable s
44、amples of the same material, the execution of the particular determination is suspect and shall be investigated and, if necessary, repeated. 8.4 Creased material For some purposes it may be necessary to determine the transmission rate of creased material; in such cases carry out the creasing procedu
45、re described in ISO2528:1974, Annex C, and then follow the procedure of method A or method B, as appropriate. 9 Expression of results Calculate the mean and standard deviation of the separate determinations carried out with face one and face two facing the wet side respectively. Express the results
46、in grams per square metre per24hg/(m 2 d) for each side, tested to two significant figures. 10 Precision 10.1 Method A No firm statement about precision can be made at this time, but work in the USA using similar principles gave a repeatability within the range2% to8% of the test value and a reprodu
47、cibility within the range7% to13% of the test value based on samples within the range2,3g/(m 2 d) to24g/(m 2 d) when tested at38 C and90% relative humidity. 10.2 Method B There is no precise information for this method at present. According to experience in the Netherlands, a repeatability of about5
48、% of the test value and a reproducibility or10% to15% of the test value can be expected from materials with WVTR in the range2g/(m 2 d) to5g/(m 2 d). 11 Test report The test report shall include the following: a) reference to this International Standard; b) the date and place of testing; c) all info
49、rmation necessary for the complete identification of the sample; d) the type of apparatus and the type of dry gas used; e) the temperature and relative humidity used as the test conditions; f) the arithmetic mean of the result for each face tested; g) the standard deviation for each face tested; h) if necessary, the results after creasing; i) any deviation from the procedure specified.BS7406:1991 4 BSI 12-1999 Figure 1 Schematic diagram of dynamic systemBS7406:1991 BSI 12-1999 5 Figure 2 Schematic diagram of static sys
