1、Designation: F3299 18Standard Test Method forWater Vapor Transmission Rate Through Plastic Film andSheeting Using an Electrolytic Detection Sensor(Coulometric P2O5Sensor)1This standard is issued under the fixed designation F3299; the number immediately following the designation indicates the year of
2、original adoption 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. Scope1.1 This test method covers a procedure for determining therate
3、 of water vapor transmission through flexible barriermaterials. The method is applicable to sheets and filmsconsisting of single or multilayer synthetic or natural polymersand foils, including coated materials. It provides for thedetermination of water vapor transmission rate (WVTR).1.2 The values s
4、tated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 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,
5、 health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of Int
6、ernational Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E96/E96M Test Methods for Water Vapor Transmission ofMaterialsE177 Practice for Use of the Terms Precision and Bias inASTM Te
7、st MethodsE178 Practice for Dealing With Outlying ObservationsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 water vapor transmission rate (WVTR), nthe timerate of water vapor flow normal to the surfaces, understead
8、y-state conditions, per unit area.3.1.1.1 DiscussionAn accepted unit of WVTR is g/m2perday (g/m224h). The test conditions of relative humidity andtemperature, where the humidity is the difference in relativehumidity across the specimens, must be stated.4. Summary of Test Method4.1 A dry chamber is s
9、eparated from a wet chamber ofknown temperature and humidity by the barrier material to betested. The dry chamber and the wet chamber make up a testcell in which the test film is sealed. Water vapor permeatingthrough the film mixes with the dry carrier gas in the drychamber and is carried to an elec
10、trolytic sensor. The carrier gasis passed through the sensor where water vapor it holds isabsorbed by phosphorous pentoxide (P2O5). Direct current,applied to electrodes of the sensor, dissociates the water intohydrogen and oxygen. Two electrons are required to electro-lyze each water molecule, and t
11、he current in the cell representsthe number of molecules dissociated per unit time.5. Significance and Use5.1 The purpose of this test method is to obtain reliablevalues for the WVTR of plastic film and sheeting.5.2 WVTR is an important property of packaging materialsand can be directly related to s
12、helf life and packaged productstability.5.3 Data from this test method is suitable as a refereemethod of testing, provided that the purchaser and seller haveagreed on sampling procedures, standardization procedures,test conditions, and acceptance criteria.6. Apparatus6.1 An example of a suitable app
13、aratus is shown in Fig. 1.It includes a test chamber consisting of two metal halves, anelectrolytic cell to determine the amount of water vaportransmitted, a flow meter, a drying device, and switch valves.1This test method is under the jurisdiction of ASTM Committee F02 on PrimaryBarrier Packaging a
14、nd is the direct responsibility of Subcommittee F02.10 onPermeation.Current edition approved May 1, 2018. Published May 2018. DOI: 10.1520/F3299-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandar
15、ds volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles o
16、n standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.16.1.1 Drying Device, shall be capable of drying the carriergas down to the detecti
17、on limit of the electrolytic cell or lower.6.1.2 Relative Humidity (RH) Generator, should be able tohumidify test gas (nitrogen) up to 90 % RH at desired testtemperature. Accuracy of measurement of RH should be 63%or better.6.1.3 Test Chamber, shall consist of two metal halves (a dryhalf and a contr
18、olled humidity half), which, when closed uponthe test specimen, will define a known sample transmissionarea (typically 50 cm2). One of the halves (not connected toelectrolytic cell) shall incorporate static O-ring in a properlyconstructed O-ring groove. The second of the halves shall havea flat rim.
19、 Since this rim is a critical sealing surface againstwhich the test specimen is pressed, it shall be smooth and flatwithout radial scratches. It is desirable to thermostaticallycontrol the temperature of the test chamber to within 60.5 C(61 F).6.1.4 Flowmeter, having an operating range from 1 to 100
20、cm3/min is required to monitor the flow rate of the nitrogenstream. Sufficiently low flow rates and/or balanced pressureson each side of the film are required to avoid stretching thespecimen.6.1.5 Electrolytic Cell, (P2O5moisture sensor) operating atan essentially constant efficiency shall be used t
21、o monitor thequantity of water vapor transmitted.6.1.6 Flow-Switching Valves, for the switching of gas flowstreams of the water vapor transmission apparatus.6.1.7 Amplifier, and associated electronics, determine elec-trolytic current, which is proportional to water vapor (mois-ture) concentration.6.
22、1.8 Computer, used to control apparatus and collect data.7. Reagents and Materials7.1 National Institute of Standards and Technology (NIST)traceable calibration gas or reference film (known WVTRmaterial) for system evaluation.7.2 Sealing Grease, a high-viscosity, silicone stopcockgrease or other sui
23、table high-vacuum grease is required forlubrication of Orings and to seal the specimen film in the testchamber.7.3 Nitrogen Gas, shall be dry and contain not less than 99.9% nitrogen.7.4 Distilled Water, for using in humidity generator.8. Sampling8.1 Film samples used for the determination of WVTR s
24、hallbe representative of materials for which the data are required.Care shall be taken to ensure that samples are representative ofconditions across the width and along the length of a roll offilm.8.2 Test specimens shall be representative of the materialand shall be free of defects including wrinkl
25、es, creases, andpinholes, unless these are characteristics of the material beingtested and included in the material description.8.3 Average thickness shall be determined 63 m using acalibrated dial gage (or equivalent) at a minimum of five pointsdistributed over the entire test area. Maximum, minimu
26、m, andKey:1 Drying device (containing e.g. a molecular sieve)2 RH Generator3 Test chamber (temperature controlled)4 Specimen5 Electrolytic cell and a flow meter6 Switch valves7 Amplifier8 ComputerFIG. 1 Measuring SystemF3299 182average values shall be recorded. Sample thickness need not bemeasured f
27、or determination of sample WVTR only.8.4 If the test specimens of an asymmetrical construction,the two surface shall be marked by appropriate distinguishingmarks and the orientation of the test specimen within thepermeation apparatus shall be reported.9. System Evaluation9.1 The electrolytic sensor
28、used in this method is a coulo-metric device that is absolute and follows Faradays Law. Atypical sensor utilizes a sensing cell coated with a thin film ofphosphorous pentoxide (P2O5). Different types of cells withwinding or flat electrodes are available. Direct current appliedto the electrodes disso
29、ciates water, absorbed by the P2O5, intohydrogen and oxygen. Two electrons are required to electro-lyze each water molecule, and the current in the cell representsthe number of molecules dissociated per second. One hundredpercent of all water vapor entering this sensor is directlyconverted to a meas
30、urable current. The relationship betweenmeasured current and moisture concentration in the electrolyticcell is governed by absolute principles of Faradays law and nocalibration versus a moisture standard is needed.9.2 Experience has shown, that under some circumstancesthe sensor may become depleted
31、or damaged. For that reason,this test method incorporates means for a periodic sensorevaluation that should be performed monthly. This evaluationcould be derived from measurements of a NIST traceablecalibration gas or “reference film” with known value. Followthe manufacturer instructions for system
32、evaluation.10. Test Procedure10.1 Test Conditions:10.1.1 Commonly accepted industry test conditions are:37.8 C 6 0.5 C and 90 % 6 3 % RH. Test conditions otherthan these shall be agreed upon by the interested parties.10.2 Preparation of Apparatus:10.2.1 If preceding tests have exposed the apparatus
33、to highmoisture levels, outgas the system to desorb residual moisturefollowing the manufacturers instructions.10.2.2 Measure the WVTR of the film specimen followingthe manufacturers instructions.10.3 Standby and Shutoff Procedures:10.3.1 Follow the manufacturers instructions for puttingthe instrumen
34、t in standby when not being used.11. Calculation11.1 Water vapor transmission rate calculated using follow-ing equation:WVTR 5IA3K (1)where:WVTR = water vapor transmission rate of the specimen,expressed in grams per square meter per dayg/m2day,A = transmission area, in square meters, of the testspec
35、imen,I = electrolytic current, in amperes, andK = 8.28 is the conversion factor for converting mea-sured electrolytic current in grams of electrolyzedwater at STP.12. Report12.1 Report the following information:12.1.1 A description of the test specimen. If the material isnonsymmetrical (two sides di
36、fferent), include a statement as towhich side was facing the high humidity,12.1.2 The sample thickness,12.1.3 The humidity environment on each side of the testfilm,12.1.4 The test temperature (to nearest 0.5 C),12.1.5 The values of WVTR, and12.1.6 A statement that the instrument was operated inaccor
37、dance with this standard method and the manufacturersrecommendations including the sensor evaluation process.13. Precision and Bias13.1 The precision of this test method is based on aninterlaboratory study conducted in 2017. Nine laboratoriestested three different film and sheeting samples at 37.8 C
38、 and90 % RH. Every “test result” represents an individualdetermination, and all laboratories reported four replicate testresults. Practice E691 was followed for the design and analysisof the data; the details are given in ASTM RR:F02-1043.313.1.1 Repeatability Limit (r)The difference between re-peti
39、tive results obtained by the same operator in a givenlaboratory applying the same test method with the sameapparatus under constant operating conditions on identical testmaterial within short intervals of time would in the long run, inthe normal and correct operation of the test method, exceed thefo
40、llowing values only in one case in 20.13.1.1.1 Repeatability can be interpreted as maximum dif-ference between two results, obtained under repeatabilityconditions, that is accepted as plausible due to random causesunder normal and correct operation of the test method.13.1.1.2 Repeatability limits ar
41、e listed in Table 1.13.1.2 Reproducibility Limit (R)The difference betweentwo single and independent results obtained by differentoperators applying the same test method in different laborato-ries using different apparatus on identical test material would,in the long run, in the normal and correct o
42、peration of the testmethod, exceed the following values only in one case in 20.3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:F02-1043. Contact ASTM CustomerService at serviceastm.org.TABLE 1 Water Vapor Transmission Rate (g/m2
43、24hrs)Material AverageRepeatabilityStandardDeviationReproducibilityStandardDeviationRepeatabilityLimitReproducibilityLimitxsrsRrR1 0.0278 0.0018 0.0054 0.0050 0.01522 0.1073 0.0033 0.0121 0.0094 0.03383 3.8402 0.0767 0.1934 0.2149 0.5415F3299 18313.1.2.1 Reproducibility can be interpreted as maximum
44、difference between two results, obtained under reproducibilityconditions, that is accepted as plausible due to random causesunder normal and correct operation of the test method.13.1.2.2 Reproducibility limits are listed in Table 1.13.1.3 The above terms (repeatability limit and reproduc-ibility lim
45、it) are used as specified in Practice E177.13.1.4 Any judgment in accordance with statements 13.1.1and 13.1.2 would have an approximate 95 % probability ofbeing correct.13.2 BiasAt the time of the study, there was no acceptedreference material suitable for determining the bias for this testmethod, t
46、herefore no statement on bias is being made.13.3 The precision statement was determined through sta-tistical examination of 96 test results, from eight laboratories,on three different materials. These three materials were de-scribed as the following:Material 1: 0.152 mm (6.0 mil) PCTFEMaterial 2: 0.
47、0508 mm (2.0 mil) PCTFEMaterial 3: 0.152 mm (6.0 mil) PET13.3.1 To judge the equivalency of two test results, it isrecommended to choose the film or sheeting material closest incharacteristics to the test material.ASTM International takes no position respecting the validity of any patent rights asse
48、rted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by
49、 the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address s
