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1、INTERNATIONAL STANDARD First edition 1990-10-15 Paper and board - Determination of water vapour transmission rate of sheet materials - Dynamic sweep and static gas methods Papier et carton - Dtifermination du coefficient de transmission de la vapeur deau des mat b) a microammeter, graduated directly
2、 in grams per square metre per 24 h g/(m* - d); c) selector and range switches; d) connection points for cells and, if desired, a re- corder. 52.2 Humidity cabinet, for storing the cells at the required conditions and having a fan for air circu- lation and small openings for entry of the plugs and c
3、ables of the cells. The required level of relative humidity may be obtained as prescribed in 4.2.3. 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. 5.2.4
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 for- mer. 5.2.5 Means of drilling holes in test pieces. 5.2.6
5、Specimen of stated water vapour trans- mission rate. 6 Sampling Select samples in accordance with IS0 186. 7 Preparation of test pieces Test pieces shall be representative of the sample and shall take into account, where appropriate, var- iations within and between sheets and batches. The test area
6、shall be free from faults likely to affect the determination. The faces shall be designated one and two respec- tively. Where the two faces of the material can be distinguished, face one shall denote the face ex- posed to the wet side in service. Carefully, in order to avoid damage to the test area,
7、 cut IO test pieces to the required size and drill holes as necessary for the test cell being used. 2) The TNO/Pira WWR 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 a
8、n endorsement by IS0 of this instrument. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 22:06:20 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 99
9、329 990(E) 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 such test pieces. The foil tape shall cover the edges and overlap the face by at least
10、 10 mm. The foil tape shall be of the self-adhesive type, using dead soft tempered foil at least 40 pm thick. Thick test pieces of homogenous construction may also allow moisture permeation through the edges and should also be treated as above. NOTE 3 No definitive statement can be given about the t
11、hickness at which sealing the edges becomes necessary, but as a general rule this should not be necessary for thicknesses less than 5 mm. 8 Procedure The precise method to be used shall be obtained from the manufacturers operation manual. The general procedure is as follows. 8.1 Method A Fill the lo
12、wer 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 the cell. Set the apparatus to the required temperature. Operate the apparatu
13、s 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 obtained with face one towards the wet side and five readings with face two tow
14、ards the wet side. 8.2 Method B Clamp the test piece in the cell with face one to- wards the wet side. Place the cell in the humidity cabinet at the required temperature and relative humidity. Record the rate of electrolysis of the water vapour passing into the cell as indicated by the microammeter
15、until a steady state has been reached. Record the reading and repeat the proce- dure so that five readings are obtained with face one towards the wet side and five readings with face two towards the wet side. 8.3 Barrier material having one face of uncoated paper Where one face of a barrier material
16、 consi sts of un- coated paper, and this face is toward s the dry si de, difficulties can be expected. All water must be re- moved from the paper by the dry gas before a con- stant water vapour transmission rate is indicated on the meter or recorder. NOTE 4 The pre-conditioning can last several days
17、 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 determi- nation yields a value grossly different from compa- rable samples of the same materi
18、al, 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 deter- mine the transmission rate of creased material; in such cases carry out the creasing procedure de- scribed in IS0 2
19、528:1974, annex C, and then follow the procedure of method A or method B, as appro- priate. 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 in grams per squar
20、e metre per 24 h g/(m*. d) for each side, tested to two signif- icant 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 princi- ples gave a repeatability within the range 2 O/o to 8 % of the test value and a reproducibil
21、ity within the range 7 % to 13 % of the test value based on sam- ples within the range 2,3 g/(m*e d) to 24 g/(m* - d) when tested at 38 “C and 90 % relative humidity. 10.2 Method B There is no precise information for this method at present. According to experience in the Netherlands, a repeatability
22、 of about 5 % of the test value and a reproducibility of 10% to 15 % of the test value can be expected from materials with WVTR in the range 2 g/(m*. d) to 5 g/(m*. d). 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards
23、 1/9972545001 Not for Resale, 04/23/2007 22:06:20 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 9932:3990(E) Flowmeter 0 Sensor (infra-red, electrolytic cell, or electrical resistance element) (Gas recirculation in some systems) I Dry gas in Desiccant column - or elec
24、trolytic cell Test piece - Enclosure maintained required temperature at I By-pass Water or saline solution Figure 1 - Schematic diagram of dynamic system Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not
25、 for Resale, 04/23/2007 22:06:20 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 9932:1990(E) I Power Enclosure maintained at required temperature and relative humidity Recorder , / l su PPlY Microammeter Figure 2 - Schematic diagram of static system owing: e) the tempe
26、rature and relative humidity used as the test conditions; f) the arithmetic mean of the result for each face andard; tested; 11 Test report The test report shall include the foll a) reference to this International St b) the date and place of testing; c) all information necessary for the complete ide
27、n- h) if necessary, the results after creasing; g) the standard deviation for each face tested; tification of the sample; i) any deviation from the procedure specified. d) the type of apparatus and the type of dry gas used; Copyright International Organization for Standardization Provided by IHS und
28、er license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 22:06:20 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 9932:1990(E) Annex A (normative) Saturated saline solutions A convenient means of obtaining a specified relative able b
29、y the use of such solutions. Table A.1 indicates humidity is to make use of a saturated saline sol- those believed to be those most likely to be required ution. A wide range of relative humidities is obtain- by users of this International Standard. Table A.1 Salt Relative humidity O/o Temperature ra
30、nge T Magnesium chloride hexahydrate (MgCI;GH,O) 33 + 2 10 to 70 - Sodium chromate dihydrate (Na,Cr,O,*LH,O) 52 + 2 20 - Sodium chloride (NaCI) 75 * 2 10 to 100 Zinc sulfate heptahydrate (ZnSO,.7H,O) 90 + 2 20 to 25 - Sodium tartrate dihydrate (Na&H,O,-2H,O) 91 3-2 20 to 40 - Copyright International
31、 Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 22:06:20 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 9932:1990(E) Annex B (normative) Calibration B.l General No specif
32、ic calibration instructions can be given in a general standard such as this, and users of this International Standard are therefore recommended to refer to the manufacturers instruction manual. A film material of known WVTR is normally supplied with the instrument and its use as required is suffi- c
33、ient to check for correct functioning of the appara- tus. Common sources of error are air leaks, residual moisture in the sweep gas, damage to the “standard” test film and, in the case of electrolytic cells, erosion of the phosphorus pentoxide coating. In any event the source of the problem must be
34、found and the appropriate remedial action taken. 16.2 Gravimetric calibration of the instrument and standard test film It may on occasions be necessary to check the cali- bration of the instrument, if for example, leakage or damage is suspected, or it may be decided to sub- stitute a different test
35、film as the standard. In such cases the following procedure may be adopted. 6.2.1 Add the saturated saline solution necessary to give the required humidity to the test cell (or hu- midity cabinet for apparatus appropriate to method B) and fix the test film in position. Run the apparatus in accordanc
36、e with the manufacturers instructions until steady conditions are obtained. Fix a charged and weighed Schwarz tube (or other equivalent ab- sorber) to the outlet of the test cell followed by a charged calcium chloride tube to prevent absorp- tion of water vapour from the atmosphere outside the test
37、cell. Run the apparatus in accordance with the manufacturers instructions until sufficient water has been absorbed in the Schwarz tube to obtain a reliable mass, at least 100 mg. Record the time taken to achieve this and weigh the Schwarz tube accurately to obtain the increase in mass. From the dete
38、rmination, calculate the mass of water vapour absorbed per hour and call this r7z1. 8.2.2 Substitute an impermeable material such as polytetrafluoroethylene coated aluminium foil (alu- minium face to the wet side) for the test film and repeat the procedure described in B.2.1, but allow the apparatus
39、 to run for at least 48 h. Calculate the mass of water vapour absorbed per hour and call this m2. NOTE 5 vz2 originates from leaks in the system or in- complete drying of the sweep gas. B.2.3 Calculate the WVTR of the test film as fol- lows: WVTR = 24(I?l, - f7IJ A where A is the exposed surface are
40、a of the test filrn in square metres. 7 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 22:06:20 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 993
41、2:1990(E) Annex C (informative) Comparison of dynamic method with gravimetric methad A limited series of tests involving materials with WVTR in the range 1 g/(m* s d) to 20 g/(m*.d) showed the dynamic method (method A) to give re- sults which were comparable but lower than those obtained by the grav
42、imetric method (IS0 2528). These results are illustrated by figure C.I. There is no known information on the comparison of the dynamic method with the static gas method. 20 z u % T 9 E 3 0 .- E 10 z 0“ / / / / / / / / / / / / / / / 0 . / / / / / / / 0 / /o / / / / / / Figure c.1 - Dynamic method com
43、pared with gravimetric method 10 Gravimetric WVTR g/(m*-d) 20 - 1-p - -P-P UDC 676.2m017.62 Descriptors: paper, paperboards, tests, determination, vapour transmission, water vapour. Price based on 8 pages -_I- _1-1_1 -I_- 8 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/23/2007 22:06:20 MDTNo reproduction or networking permitted without license from IHS -,-,-