1、Designation: F1249 06 (Reapproved 2011)Standard Test Method forWater Vapor Transmission Rate Through Plastic Film andSheeting Using a Modulated Infrared Sensor1This standard is issued under the fixed designation F1249; the number immediately following the designation indicates the year oforiginal ad
2、option 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 of water v
3、apor transmission through flexible barriermaterials. The method is applicable to sheets and films up to 3mm (0.1 in.) in thickness, consisting of single or multilayersynthetic or natural polymers and foils, including coatedmaterials. It provides for the determination of (1) water vaportransmission r
4、ate (WVTR), (2) the permeance of the film towater vapor, and (3) for homogeneous materials, water vaporpermeability coefficient.NOTE 1Values for water vapor permeance and water vapor perme-ability must be used with caution. The inverse relationship of WVTR tothickness and the direct relationship of
5、WVTR to the partial pressuredifferential of water vapor may not always apply.1.2 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 and health practices and determ
6、ine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D374 Test Methods for Thickness of Solid Electrical Insu-lationD1898 Practice for Sampling of Plastics3E96/E96M Test Methods for Water Vapor Transmission ofMaterialsE104 Practice for Maintaining
7、Constant Relative Humidityby Means of Aqueous SolutionsE178 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 permeability coeffcientthe product ofthe permeanc
8、e and the thickness of the film. The permeabilityis meaningful only for homogeneous materials, in which caseit is a property characteristic of bulk material.3.1.1.1 DiscussionThis quantity should not be used unlessthe relationship between thickness and permeance has beenverified in tests using sever
9、al thicknesses of the material. Anaccepted unit of permeability is the metric perm centimeter, or1 g/m2per day per mm Hgcm of thickness. The SI unit is themol/m2sPamm. The test conditions (see 3.1) must be stated.3.1.2 water vapor permeancethe ratio of a barriersWVTR to the vapor pressure difference
10、 between the twosurfaces.3.1.2.1 DiscussionAn accepted unit of permeance is themetric perm, or 1 g/m2per day per mm Hg. The SI unit is themol/m2sPa. Since the permeance of a specimen is generally afunction of relative humidity and temperature, the test condi-tions must be stated.3.1.3 water vapor tr
11、ansmission rate (WVTR)the time rateof water vapor flow normal to the surfaces, under steady-stateconditions, per unit area.3.1.3.1 DiscussionAn accepted unit of WVTR is g/m2perday. The test conditions of relative humidity and temperaturewhere the humidity is the difference in relative humidity acros
12、sthe specimens, must be stated.4. Summary of Test Method4.1 A dry chamber is separated from a wet chamber ofknown temperature and humidity by the barrier material to betested. The dry chamber and the wet chamber make up adiffusion cell in which the test film is sealed. Water vapordiffusing through t
13、he film mixes with the gas in the drychamber and is carried to a pressure-modulated infrared sensor.This sensor measures the fraction of infrared energy absorbedby the water vapor and produces an electrical signal, theamplitude of which is proportional to water vapor concentra-tion. The amplitude of
14、 the electrical signal produced by the test1This test method is under the jurisdiction of ASTM Committee F02 on FlexibleBarrier Packaging and is the direct responsibility of Subcommittee F02.10 onPermeation.Current edition approved Aug. 1, 2011. Published November 2011. Originallyapproved in 1989. L
15、ast previous edition approved in 2006 as F1249 06. DOI:10.1520/F1249-06R11.2For 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 onthe
16、 ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.film is then compared to the signal produced by measurementof a calibration
17、film of known water vapor transmission rate.This information is then used to calculate the rate at whichmoisture is transmitted through the material being tested.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
18、is an important property of packaging materialsand can be directly related to shelf 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 c
19、onditions, and acceptance criteria.6. Apparatus6.1 This method utilizes water vapor transmission appara-tus4(Fig. 1) comprised of the following:6.1.1 Diffusion CellAn assembly consisting of two metalhalves which, when closed upon the test specimen, willaccurately define a circular area. A typical ac
20、ceptable diffusioncell area is 50 cm2. The volume enclosed by each cell half,when clamped, is not critical; it should be small enough toallow for rapid gas exchange, but not so small that anunsupported film that happens to sag or buckle will contact thetop or bottom of the cell. A depth of approxima
21、tely 6 mm(0.250 in.) has been found to be satisfactory for 50-cm2cells.6.1.1.1 Diffusion Cell ORingAn appropriately sizedgroove machined into the humid chamber side of the diffusioncell retains a neoprene Oring. The test area is considered to bethe area established by the inside contact diameter of
22、thecompressed Oring when the diffusion cell is clamped shutagainst the test specimen.6.1.1.2 Diffusion Cell Sealing SurfaceA flat rim aroundthe dry side of the diffusion cell. This is a critical sealingsurface against which the test specimen is pressed; it shall besmooth and without radial scratches
23、.6.1.1.3 Diffusion Cell Air PassagesTwo holes in the dryhalf of the diffusion cell. This is necessary only in the earliermodel WVTR instruments that have a separate conditioningrack and testing chamber. These shall incorporate Oringssuitable for sealing the diffusion cell to the test chamberpneumati
24、c fittings for the introduction and exhaust of airwithout significant loss or leakage.NOTE 2Use of Multiple Diffusion CellsExperience has shown thatarrangements using multiple diffusion cells are a practical way to increasethe number of measurements that can be obtained in a given time. Aseparate co
25、nditioning rack (Fig. 2) may be used that contains a manifoldwhich connects the dry-chamber side of each individual diffusion cell toa dry-air source. Dry air is continually purging the dry chamber of thosecells that are connected to the conditioning rack while the humid chamberside is held at a spe
26、cific relative humidity by distilled water or asaturated-salt solution. It is desirable to thermostatically control thetemperature of the conditioning rack as described in 6.1.3.6.1.2 Test ChamberA cavity into which the diffusion cellis inserted. Again, this is necessary only in the earlier modelWVT
27、R instruments that have a separate conditioning rack andtesting chamber. The test chamber shall incorporate means forclamping the diffusion cell in accurate registration with pneu-matic system openings to the dry-air source and the infrareddetector. The chamber shall also provide a thermometer wellf
28、or the measurement of temperature.6.1.3 Diffusion Cell Temperature ControlIt is desirable tothermostatically control the temperature of the diffusion cell towithin 61F.Asimple resistive heater attached to the station insuch a manner as to ensure good thermal contact is adequatefor this purpose.Ather
29、mistor sensor and an appropriate controlcircuit will serve to regulate the temperature unless measure-ments are being made close to ambient temperature. In thatcase it may be necessary to provide cooling coils to removesome of the heat.6.1.4 FlowmeterA means for regulating the flow of dryair within
30、an operating range of 5 to 100 cc/min is required.6.1.5 Flow-Switching Valves, for the switching of dry-gasflow streams of the water vapor transmission apparatus.4The sole source of supply of the apparatus known to the committee at this timeis Mocon/Modern Controls, Inc., 7500 Boone Avenue North, Mi
31、nneapolis, MN55428. If you are aware of alternative suppliers, please provide this information toASTM International Headquarters. Your comments will receive careful consider-ation at a meeting of the responsible technical committee,1which you may attend.FIG. 1 Measuring SystemFIG. 2 Conditioning Sys
32、temF1249 06 (2011)26.1.6 Infrared SensorA water vapor detector capable ofsensing 1 g/L of water, or, in other terms, 1 ppm by volume,or 0.002 % relative humidity at 37.8C.6.1.7 Recording DeviceA multirange strip chart recorderor other appropriate instrument for measuring the voltagedeveloped by the
33、signal amplifier.6.1.8 Desiccant Drying System, shall be capable of reducingthe concentration of water vapor in the gas source down to lessthan 0.5 ppm by volume or 0.001 % relative humidity at37.8C. In earlier model WVTR equipment, a separate desic-cant drying system is needed for the conditioning
34、rack and testchamber.6.1.9 Flow-Metering ValveA fine-metering valve capableof controlling the dry-gas flow rate to the test cell when theapparatus is in the “measure mode of operation.7. Reagents and Materials7.1 Desiccant,4,5for drying gas stream.7.2 Absorbent Pads (not critical), such as filter pa
35、ds of 30to 75 mm in diameter. Necessary only in earlier model WVTRequipment that utilizes distilled water or saturated salt solu-tions to generate the desired relative humidity.7.3 Distilled Water, for producing 100 % relative humidity,or various saturated salt solutions to produce other relativehum
36、idities as described in Practice E104. Newer WVTRequipment does not require saturated salt solutions. Refer tothe manufacturers instructions for generating relative humid-ity.7.4 Reference Film, known WVTR material for systemcalibration.7.5 Sealing Grease, a high-viscosity, silicone stopcockgrease o
37、r other suitable high-vacuum grease is required forlubrication of Orings and to seal the specimen film in thediffusion cell.7.6 Nitrogen Gas, shall be dry and contain not less than99.5 % nitrogen. Needed only with certain WVTR instruments.8. Sampling8.1 Select material for testing in accordance with
38、 standardmethods of sampling applicable to the material under test.Sampling may be done in accordance with Practice D1898.Select samples considered representative of the material to betested. If the material is of nonsymmetrical construction, theorientation should be noted.9. System Calibration With
39、 Reference Film9.1 Follow the manufacturers instructions for calibratingthe WVTR instrument with a reference film.10. Test Procedure10.1 Preparation of Apparatus (Fig. 1)If preceding testshave exposed the apparatus to high moisture levels, outgas thesystem to desorb residual moisture.10.2 Number of
40、Specimens TestedTest enough specimensto characterize package permeation rates but never less thanthree per sample.10.3 Preparation of Test Samples:10.3.1 Cut the test specimen to approximately 10 cm by 10cm (4 in. by 4 in.).10.3.2 Measure specimen thickness at four equally spacedpoints within the te
41、st area and at the center in accordance withguidelines described in Test Method D374.10.3.3 Lightly grease the cell sealing surface and the cellOring.10.3.4 For earlier model WVTR systems that require the useof distilled water or saturated salt solutions, insert one to threeabsorbent pads into the l
42、ower half-cell and dampen withdistilled water or a desired salt solution. Otherwise, for newerWVTR instruments, follow the manufacturers instructions forgenerating the desired relative humidity.10.3.5 Affix the test film to the diffusion cell following themanufacturers instructions. Fig. 3 shows the
43、 type of diffusioncell used in earlier model WVTR equipment that consisted ofa separate conditioning rack and testing chamber. Diffusioncells in newer WVTR equipment are similar to the lower halfof the cell displayed in Fig. 3.10.3.6 If using a separate conditioning rack, clamp theassembled cell in
44、the conditioning rack. Allow the film tocondition in the diffusion cell until steady state has beenattained. If unfamiliar with the material being tested, theoperator should investigate the effect of conditioning time to becertain that sufficient time has been allowed for the material toequilibrate
45、under the test conditions (see Note 3).10.4 Measure the WVTR of the film specimen following themanufacturers instructions.NOTE 3When testing materials for which the operator has no previoushistory, additional time must be allowed to assure that true equilibrium hasbeen reached. When in doubt, retest
46、 after an additional conditioninginterval of several hours.10.5 Record temperature of each test with reference to athermometer or thermocouple installed in the test chamberthermometer well. Temperature is a critical parameter affectingthe measurement of WVTR. During testing, monitor thetemperature,
47、periodically, to the nearest 0.5C. Report theaverage temperature and the range of temperatures observedduring the test.10.6 Standby and Shutoff Procedures:10.6.1 Follow the manufacturers instructions for puttingthe instrument in standby when not being used.5Linde Molecular Sieve, Type 4Aor Type 5A,
48、in the form of18 in. pellets as maybe obtained from the Union Carbide Co., Linde Division, Danbury, CT 06817-0001.FIG. 3 Film Diffusion CellF1249 06 (2011)310.6.2 When the system is not to be used for an extendedperiod and there are no films that require conditioning, theelectrical power may be turn
49、ed off.11. Calculation11.1 WVTRIf using a recorder, calculate water vaportransmission rate using the formula:WVTR 5 C ES 2 EO!where:C = a calibration factor expressing rate as a function ofvoltage (or mV). The value of C is derived from testsof a known reference film (Section 9),EO = permeation system zero level voltage, andES = equilibrium voltage obtained with the test specimen.Newer computer-controlled systems will automatically cal-culate the WVTR.11.2 PermeanceCalculate sample permeance (if required)using the following rela
