1、Designation: E398 03 (Reapproved 2009)1E398 13Standard Test Method forWater Vapor Transmission Rate of Sheet Materials UsingDynamic Relative Humidity Measurement1This standard is issued under the fixed designation E398; the number immediately following the designation indicates the year oforiginal a
2、doption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1 NOTEUnits information was revised editorially in May 2009.1. Scope1.1 This test
3、 method covers dynamic evaluation of the rate of transfer of water vapor through a flexible barrier material andallows conversion to the generally recognized units of water vapor transmission (WVT) as obtained by various other test methodsincluding the gravimetric method described in Test Methods E9
4、6/E96M.1.2 LimitationsThis test method is limited to flexible barrier sheet materials composed of either completely hydrophobicmaterials, or combinations of hydrophobic and hydrophilic materials having at least one surface that is hydrophobic.1.3 The minimum test value obtained by this test method i
5、s limited by the leakage of water vapor past the clamping seals ofthe test instrument. A reasonable value may be approximately 0.01 g/24 hm 2 for any WVTR method including the desiccantprocedure of Test Methods E96/E96M at 37.8C, and 90 % relative humidity. This limit can be checked for each instrum
6、ent withan impervious specimen such as aluminum foil. Calibration procedures can compensate for the leakage rate if so stated.1.4 This test method is not suitable for referee testing at this time, but is suitable for control testing and material comparison.1.5 Several other ASTM test methods are ava
7、ilable to test a similar property. This test method is unique in that it closelyduplicates typical product storage where a transfer of moisture from a package into the environment is allowed to proceed withoutconstantly sweeping the environmental side with dry gas. Methods with constantly swept dry
8、sides include Test Methods F1249,F372, and F1770.1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsi
9、bilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C168 Terminology Relating to Thermal InsulationE96/E96M Test Methods for Water Vapor Transmission o
10、f MaterialsE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodF17 Terminology Relating to Flexible Barrier PackagingF372 Test Method for Water Vapor Transmission Rate of Flexible B
11、arrier Materials Using an Infrared Detection Technique(Withdrawn 2009)3F1249 Test Method for Water Vapor Transmission Rate Through Plastic Film and Sheeting Using a Modulated Infrared SensorF1770 Test Method for Evaluation of Solubility, Diffusivity, and Permeability of Flexible Barrier Materials to
12、 Water Vapor(Withdrawn 2004)31 This test method is under the jurisdiction ofASTM Committee F02 on Flexible Barrier Packaging and is the direct responsibility of Subcommittee F02.10 on Permeation.A previous version was under the jurisdiction of ASTM Committee C16.Current edition approved May 1, 2009O
13、ct. 1, 2013. Published June 2009November 2013. Originally approved in 1970. Last previous edition approved in 20032009 asE398 03.E398 03(2009)1. DOI: 10.1520/E0398-03R09E01.10.1520/E0398-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at servic
14、eastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user of an
15、ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as publish
16、ed by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 DefinitionsFor definitions of terms concerning the transmission of water vapor refer to Terminologies C168 and F17.
17、4. Summary of Test Method4.1 The specimen is mounted between two chambers, one of relatively high relative humidity and the other of relatively lowrelative humidity. After conditioning and isolation of chambers, the rate at which the moisture increases within the relatively lowrelative humidity cham
18、ber over a predetermined range of interest is measured. This rate is compared to the rate for a calibrationsample (calibrated gravimetrically) and the WVTR is determined.5. Significance and Use5.1 No single set of test conditions can represent all climatic and use conditions, so this WVTR test metho
19、d serves more tocompare different materials at a stated set of conditions than to predict their actual performance in the field under any conditions.5.2 The water vapor transmission rate, under known and carefully controlled conditions, may be used to evaluate the vaporbarrier qualities of a sheet.
20、Direct correlation of values obtained under different conditions of test temperature and relative humiditywill be valid provided the barrier material under test does not undergo changes in solid state (such as a crystalline transition ormelting point) at or between the conditions of test.6. Apparatu
21、s6.1 The apparatus employed should have the following elements:6.1.1 Test Cell, designed to clamp a defined sample area sufficiently large to be representative of the sample (an area of 50 cm2has been shown to be satisfactory) between two chambers, one to contain an atmosphere of low relative humidi
22、ty (sensor-sidechamber), and the other an atmosphere of higher relative humidity (humidified chamber) (see Fig. 1).6.1.2 Clamping Arrangement, to allow rapid insertion and removal of the test specimen equipped with gaskets against whichthe specimen is held to the dry chamber by a clamping force suff
23、icient to resist leakage.6.1.3 Humidification Provision, for maintaining humidity in the wet cell at the desired level. Where an atmosphere close tosaturation is required, this may be achieved by means of a reservoir of water or a saturated sponge provided there is a spacing 8mm or less, between the
24、 water source and the specimen and yet no direct contact. Other levels of relative humidity may be obtainedwith saturated salt solutions or a stream of controlled humidified air.6.1.4 Air SourceAir dried below the operating humidity range of the instrument (5 % relative humidity or less) shall be us
25、edas a purge for the sensor-side chamber. Various desiccants have been found satisfactory as drying agents.6.1.5 Sensor, with rapid response and sensitivity capable of detecting changes in the moisture content of the gas within the drychamber of 0.05 % relative humidity or less. This sensor may take
26、 any of a number of forms. For this purpose, the following havebeen described in the literature: an electrical resistance element,4 an electrolytic cell,5 and a beam of infrared radiation.64 Ranger, H. O., and Gluckman, M. J., Modern Packaging , Vol 37, No. 11, July 1964, p. 153.5 Toren, P. E., Anal
27、ytical Chemistry, Vol 37, 1965, p. 922.6 Husband, R. M., and Petter, P. J., Tappi, Vol 49, 1966, p. 565.FIG. 1 Sectional Diagram of a Typical Test Chamber Using Relative Humidity SensingE398 1326.1.6 Data Collection, a means to convert the sensors moisture-change response into a signal that can be u
28、sed to calculate thepassage of moisture through the material under test. This may take the form of registering the time required for the signal to passbetween two selected levels of relative humidity, or the change in signal over a given interval of time.6.1.7 Temperature Control, a means of maintai
29、ning the test-cell purge air and the test specimen at a constant known temperaturewithin 60.1C is provided.6.1.8 Standard Films, which have been calibration by gravimetric means. Various films have been found satisfactory withvarious thicknesses of PET most commonly used.7. Test Specimens or Sample7
30、.1 Test specimens shall be representative of the sample.7.2 Where the test specimen is completely hydrophobic, no special conditioning procedure is required except that the surfaceexposed in the dry cell must not have visible free water present.7.3 For specimens containing a hydrophilic layer, consi
31、deration must be given to its orientation. If the hydrophilic layer, suchas paper, is facing the dry side of the test apparatus, false readings may result.8. Testing Conditions and Instrument Test Range8.1 The conditions for the test are selected. In the U.S.A., a standard condition of 37.8C and 90
32、or 100 % relative humiditydifferential is commonly used, but the level can be whatever condition is of interest. If a different driving force is used in the testthan is to be reported, a linear adjustment can be made if it has been demonstrated that the material does not undergo solid-statechanges a
33、t these conditions. The use of such an adjustment is to be clearly stated in the report.8.2 The instrument normally uses a reservoir of water to produce 100 % relative humidity in the high relative humidity chamber.The sensor-side chamber is purged with dry air prior to testing, but the relative hum
34、idity when measuring WVTR can be any leveldesired below the level of the wet cell and within the calibrated range. A dry cell level of nominally 10 % or 35 % is commonlyused, but other levels can be used as desired. The final report will state the conditions of the wet and dry chambers. If 100 % for
35、the wet chamber and 10 % for the dry chamber are used, this will yield a driving force of 90 % relative humidity (100 % versus10 %). The driving force for other combinations of wet and dry chamber conditions shall be similarly calculated.8.3 The instrument is set to record the time to change from 0.
36、160.05 % below to 0.160.05 % above this nominal dry chambercondition. The actual relative humidity used for the end points will be known.9. Calibration and Standardization9.1 The response of the relative humidity sensor is calibrated with a NIST certified humidity sensor. This is accomplished either
37、with (1) The instrument sensor in place and a means of exposing the certified sensor to the known humidified gas stream or (2)The instrument sensor removed from the instrument and calibrated. The relative humidity used for this calibration shall cover therange of actual relative humidity used during
38、 testing.9.2 A standard, calibration film whose WVTR has been gravimetrically determined (referred in 10.7 as WVTRc) in accordancewith the desiccant method of Test Methods E96/E96M is tested in the instrument as described below. The time for the relativehumidity to change through the range selected
39、is noted. (Referred in 10.7 as TC = Time to move through humidity range forcalibration film).10. Procedure10.1 Cut the specimen to the proper size for the test cell being used.10.2 Orient the specimen appropriately.10.2.1 In dynamic test procedures, the presence of a water-sensitive surface in the d
40、ry chamber may result in a reproducible butfalse reading due in part to edge effects. Tests in this orientation cannot reliably be made by this procedure.10.3 Purge the dry chamber with the dried, purge air until the cell and exposed specimen surface are at equilibrium at a lowerhumidity condition t
41、han that employed for the test cycle.10.4 Shut off the purge air and isolate the sensor containing chamber from the surrounding atmosphere. Allow the cell andspecimen to begin to return to balance as moisture permeates through the film under test until the initial humidity desired to startthe test i
42、s reached.10.5 Measure and record the time for the relative humidity within the dry chamber changes from 0.1 6 0.05 % below thenominal dry condition to 0.1 6 0.05 % above the nominal condition. Conditions for the test samples must be the same as for thecalibration sample.10.6 Repeat steps 10.3 to 10
43、.5 without removing the specimen until successive readings of the time to transverse the humidityrange are uniform. The resulting value is taken as the test result for that specimen.E398 13310.7 The WVTR for the sample under test is calculated by comparing its time to the time required for the calib
44、ration film.WVTRT 5WVTRCTCTT (1)where:WVTRT = WVTR of sample under test,WVTRC = WVTR determined gravimetrically,TT = time to move through humidity range for sample under test, andTC = time to move through humidity range for calibration film.11. Report11.1 The WVTR can be calculated as described in 1
45、0.7 and reported with appropriate significant figures.11.2 When suitable test limits have been developed with samples of known acceptance, the dynamic test results in terms ofseconds or humidity units may be reported directly, if desired.11.3 Test conditions (including temperature, relative humidity
46、) are reported along with a complete description of the instrumentused.12. Precision and Bias12.1 The precision stated below of this test method is based on experience an interlaboratory study of Test Method E398in onelaboratory with , Standard Test Method for Water Vapor Transmission Rate of Sheet
47、Materials Using Dynamic Relative HumidityMeasurement, conducted in 2012. Each of seven laboratories tested seven different materials. Every “test result” represents anindividual determination, and all participants reported duplicate WVTR test results. Practice E691the Honeywell W825A WVTRunit. was f
48、ollowed for the design and analysis of the data.12.1.1 Repeatability (within a laboratory)(r)9 %.The difference between repetitive results obtained by the same operatorin a given laboratory applying the same test method with the same apparatus under constant operating conditions on identical testmat
49、erial within short intervals of time would in the long run, in the normal and correct operation of the test method, exceed thefollowing values only in one case in 20.12.1.1.1 Repeatability can be interpreted as maximum difference between two results, obtained under repeatability conditions,that is accepted as plausible due to random causes under normal and correct operation of the test method.12.1.1.2 Repeatability limits are listed in Table 1.12.1.2 Comparability (between materials)Reproducibility (R) not known.The difference between two single and indepen-
