1、Designation: E 398 03Standard Test Method forWater Vapor Transmission Rate of Sheet Materials UsingDynamic Relative Humidity Measurement1This standard is issued under the fixed designation E 398; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers dynamic evaluation of the rateof transfer of water vapor through a f
3、lexible barrier materialand allows conversion to the generally recognized units ofwater vapor transmission (WVT) as obtained by various othertest methods including the gravimetric method described inTest Methods E 96.1.2 LimitationsThis test method is limited to flexiblebarrier sheet materials compo
4、sed of either completely hydro-phobic materials, or combinations of hydrophobic and hydro-philic materials having at least one surface that is hydrophobic.1.3 The minimum test value obtained by this test method islimited by the leakage of water vapor past the clamping sealsof the test instrument. A
5、reasonable value may be approxi-mately 0.01 g/24 hm2for any WVTR method including thedesiccant procedure of Test Methods E 96 at 37.8C (100F),and 90 % relative humidity. This limit can be checked for eachinstrument with an impervious specimen such as aluminumfoil. Calibration procedures can compensa
6、te for the leakagerate if so stated.1.4 This test method is not suitable for referee testing at thistime, but is suitable for control testing and material compari-son.1.5 The values stated in SI units are to be regarded asstandard. The values gives in parentheses are provided forinformation purposes
7、 only.1.6 Several other ASTM test methods are available to test asimilar property. This test method is unique in that it closelyduplicates typical product storage where a transfer of moisturefrom a package into the environment is allowed to proceedwithout constantly sweeping the environmental side w
8、ith drygas. Methods with constantly swept dry sides include TestMethods F 1249, ASTM F 372, and ASTM F 1770.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety
9、and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 168 Terminology Relating to Thermal InsulationC 677 Practice for Use of a Polyethylene TerephthalateReference Film for the Measurement of the Time-Averaged Vapor
10、Pressure in a Controlled Humidity Space3E 96/E 96M Test Methods for Water Vapor Transmission ofMaterialsF17 Terminology Relating to Flexible Barrier MaterialsF 372 Test Method for Water Vapor Transmission Rate ofFlexible Barrier Materials Using an Infrared DetectionTechniqueF 1249 Test Method for Wa
11、ter Vapor Transmission RateThrough Plastic Film and Sheeting Using a ModulatedInfrared SensorF 1770 Test Method for Evaluation of Solubility, Diffusiv-ity, and Permeability of Flexible Barrier Materials to WaterVapor33. Terminology3.1 DefinitionsFor definitions of terms concerning thetransmission of
12、 water vapor refer to Terminologies C 168 andF17.4. Summary of Test Method4.1 The specimen is mounted between two chambers, one ofrelatively high relative humidity and the other of relatively lowrelative humidity. After conditioning and isolation of cham-bers, the rate at which the moisture increase
13、s within the1This test method is under the jurisdiction of ASTM Committee F02 on FlexibleBarrier Materials and is the direct responsibility of Subcommittee F02.10 onPermeation. A previous version was under the jurisdiction of ASTM CommitteeC16.Current edition approved May 10, 2003. Published July 20
14、03. Originallyapproved in 1970. Discontinued in 1994 and reinstated as E 39803.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page o
15、nthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.relatively low relative humidity chamber over a predeterminedrange of interest is measured. This rate is compared to the ratefor a calibration sample (calib
16、rated gravimetrically) and theWVTR is determined.5. Significance and Use5.1 No single set of test conditions can represent all climaticand use conditions, so this WVTR test method serves more tocompare different materials at a stated set of conditions than topredict their actual performance in the f
17、ield under any condi-tions.5.2 The water vapor transmission rate, under known andcarefully controlled conditions, may be used to evaluate thevapor barrier qualities of a sheet. Direct correlation of valuesobtained under different conditions of test temperature andrelative humidity will be valid prov
18、ided the barrier materialunder test does not undergo changes in solid state (such as acrystalline transition or melting point) at or between theconditions of test.6. Apparatus6.1 The apparatus employed should have the followingelements:6.1.1 Test Cell, designed to clamp a defined sample areasufficie
19、ntly large to be representative of the sample (an area of50 cm2has been shown to be satisfactory) between twochambers, one to contain an atmosphere of low relativehumidity (sensor-side chamber), and the other an atmosphereof higher relative humidity (humidified chamber) (see Fig. 1).6.1.2 Clamping A
20、rrangement, to allow rapid insertion andremoval of the test specimen equipped with gaskets againstwhich the specimen is held to the dry chamber by a clampingforce sufficient to resist leakage.6.1.3 Humidification Provision, for maintaining humidity inthe wet cell at the desired level. Where an atmos
21、phere close tosaturation is required, this may be achieved by means of areservoir of water or a saturated sponge provided there is aspacing 8 mm (0.31 in.) or less, between the water source andthe specimen and yet no direct contact. Other levels of relativehumidity may be obtained with saturated sal
22、t solutions or astream of controlled humidified air.6.1.4 Air SourceAir dried below the operating humidityrange of the instrument (5 % relative humidity or less) shall beused as a purge for the sensor-side chamber. Various desiccantshave been found satisfactory as drying agents.6.1.5 Sensor, with ra
23、pid response and sensitivity capable ofdetecting changes in the moisture content of the gas within thedry chamber of 0.05 % relative humidity or less. This sensormay take any of a number of forms. For this purpose, thefollowing have been described in the literature: an electricalresistance element,4
24、an electrolytic cell5and a beam of infraredradiation.66.1.6 Data Collection, a means to convert the sensorsmoisture-change response into a signal that can be used tocalculate the passage of moisture through the material undertest. This may take the form of registering the time required forthe signal
25、 to pass between two selected levels of relativehumidity, or the change in signal over a given interval of time.6.1.7 Temperature Control, a means of maintaining thetest-cell purge air and the test specimen at a constant knowntemperature within 60.1C (60.18F) is provided.6.1.8 Standard Films, which
26、have been calibration by gravi-metric means. Various films have been found satisfactory withvarious thicknesses of PET most commonly used.7. Test Specimens or Sample7.1 Test specimens shall be representative of the sample.4Ranger, H. O., and Gluckman, M. J., Modern Packaging, Vol 37, No. 11, July196
27、4, p. 153.5Toren, P. E., Analytical Chemistry, Vol 37, 1965, p. 922.6Husband, R. M., and Petter, P. J., Tappi, Vol 49, 1966, p. 565.FIG. 1 Sectional Diagram of a Typical Test Chamber Using Relative Humidity SensingE3980327.2 Where the test specimen is completely hydrophobic, nospecial conditioning p
28、rocedure is required except that thesurface exposed in the dry cell must not have visible free waterpresent.7.3 For specimens containing a hydrophilic layer, consider-ation must be given to its orientation. If the hydrophilic layer,such as paper, is facing the dry side of the test apparatus, falsere
29、adings may result.8. Testing Conditions and Instrument Test Range8.1 The conditions for the test are selected. In the U.S.A., astandard condition of 100F (37.8C) and 90 or 100 % relativehumidity differential is commonly used, but the level can bewhatever condition is of interest. If a different driv
30、ing force isused in the test than is to be reported, a linear adjustment canbe made if it has been demonstrated that the material does notundergo solid-state changes at these conditions. The use ofsuch an adjustment is to be clearly stated in the report.8.2 The instrument normally uses a reservoir o
31、f water toproduce 100 % relative humidity in the high relative humiditychamber. The sensor-side chamber is purged with dry air priorto testing, but the relative humidity when measuring WVTRcan be any level desired below the level of the wet cell andwithin the calibrated range. A dry cell level of no
32、minally 10 %or 35 % is commonly used, but other levels can be used asdesired. The final report will state the conditions of the wet anddry chambers. If 100 % for the wet chamber and 10 % for thedry chamber are used, this will yield a driving force of 90 %relative humidity (100 % versus 10 %). The dr
33、iving force forother combinations of wet and dry chamber conditions shall besimilarly calculated.8.3 The instrument is set to record the time to change from0.1 6 0.05 % below to 0.1 6 0.05 % above this nominal drychamber condition. The actual relative humidity used for theend points will be known.9.
34、 Calibration and Standardization9.1 The response of the relative humidity sensor is cali-brated with a NIST certified humidity sensor. This is accom-plished either with (1) The instrument sensor in place and ameans of exposing the certified sensor to the known humidifiedgas stream or (2) The instrum
35、ent sensor removed from theinstrument and calibrated. The relative humidity used for thiscalibration shall cover the range of actual relative humidityused during testing.9.2 A standard, calibration film whose WVTR has beengravimetrically determined (referred in 10.7 as WVTRc)inaccordance with the de
36、siccant method of Test Methods E 96 istested in the instrument as described below. The time for therelative humidity to change through the range selected is noted.(Referred in 10.7 as TC= Time to move through humidityrange for calibration film).10. Procedure10.1 Cut the specimen to the proper size f
37、or the test cellbeing used.10.2 Orient the specimen appropriately.10.2.1 In dynamic test procedures, the presence of a water-sensitive surface in the dry chamber may result in a reproduc-ible but false reading due in part to edge effects. Tests in thisorientation cannot reliably be made by this proc
38、edure.10.3 Purge the dry chamber with the dried, purge air untilthe cell and exposed specimen surface are at equilibrium at alower humidity condition than that employed for the test cycle.10.4 Shut off the purge air and isolate the sensor containingchamber from the surrounding atmosphere. Allow the
39、cell andspecimen to begin to return to balance as moisture permeatesthrough the film under test until the initial humidity desired tostart the test is reached.10.5 Measure and record the time for the relative humiditywithin the dry chamber changes from 0.1 6 0.05 % below thenominal dry condition to
40、0.1 6 0.05 % above the nominalcondition. Conditions for the test samples must be the same asfor the calibration sample.10.6 Repeat steps 10.3 to 10.5 without removing the speci-men until successive readings of the time to transverse thehumidity range are uniform. The resulting value is taken as thet
41、est result for that specimen.10.7 The WVTR for the sample under test is calculated bycomparing its time to the time required for the calibration film.WVTRT5 WVTRC TC4 TT(1)where:WVTRT= WVTR of sample under test,WVTRC= WVTR determined gravimetrically,TT= time to move through humidity range forsample
42、under test, andTC= time to move through humidity range for cali-bration film.11. Report11.1 The WVTR can be calculated as described in 10.7 andreported with appropriate significant figures.11.2 When suitable test limits have been developed withsamples of known acceptance, the dynamic test results in
43、 termsof seconds or humidity units may be reported directly, ifdesired.11.3 Test conditions (including temperature, relative humid-ity) are reported along with a complete description of theinstrument used.12. Precision and Bias12.1 The precision stated below is based on experience inone laboratory w
44、ith the Honeywell W825A WVTR unit.12.1.1 Repeatability (within a laboratory)69%.12.1.2 Comparability (between materials)not known.12.1.3 Reproducibility (between materials)610 %.12.2 Experience in another laboratory using a Honeywellunit indicates that repeatability for specimens of less than 0.3ng/
45、(Pasm2) (0.005 perm) is 625 %, for less than 1.00ng/(Pasm2) (0.02 perm) is 610 %. For 57 ng/(Pasm2) (1.0perm) is 67 %, and for greater than 57 ng/(Pa sm2) (1.0 perm)is 61.6 %.12.3 No significant interlaboratory correlations have yetbeen made, but are underway at the time of the writing of thisrevisi
46、on (November 2002). A common precision and biasstatement is anticipated for a number of standard test methods,which measure WVTR using various instruments.E39803313. Keywords13.1 dynamic measurement; flexible barrier materials; rela-tive humidity; sheet material; water vapor transmissionASTM Interna
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