1、Designation: F 1249 06Standard Test Method forWater Vapor Transmission Rate Through Plastic Film andSheeting Using a Modulated Infrared Sensor1This standard is issued under the fixed designation F 1249; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e case 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.NoteParagraph 13.1.1 was editorially corrected and the year date was changed on June 22, 2006.1.
3、Scope1.1 This test method covers a procedure for determining therate of water vapor 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 coat
4、edmaterials. It provides for the determination of (1) water vaportransmission rate (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 cautio
5、n. The inverse relationship of WVTR tothickness and the direct relationship of 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
6、 this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 374 Test Methods for Thickness of Solid Electrical Insu-lationD 1898 Practice for Sampling of Plastics3E 96/E 96M
7、Test Methods for Water Vapor Transmission ofMaterialsE 104 Practice for Maintaining Constant Relative Humidityby Means of Aqueous SolutionsE 178 Practice for Dealing With Outlying ObservationsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminol
8、ogy3.1 Definitions:3.1.1 water vapor permeability coeffcientthe product ofthe permeance 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 unless
9、the relationship between thickness and permeance has beenverified in tests using several 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
10、.1.2 water vapor permeancethe ratio of a barriersWVTR to the vapor pressure difference 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 relat
11、ive humidity and temperature, the test condi-tions must be stated.3.1.3 water vapor transmission 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 h
12、umidity and temperaturewhere the humidity is the difference in relative humidity acrossthe 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 ma
13、ke up a1This test method is under the jurisdiction of ASTM Committee F02 on FlexibleBarrier Materials and is the direct responsibility of Subcommittee F02.10 onPermeation.Current edition approved June 22, 2006. Published June 2006. Originallyapproved in 1989. Last previous edition approved in 2005 a
14、s F 1249 05.2For 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 ASTM website.3Withdrawn.1Copyright ASTM International, 100 Bar
15、r Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.diffusion cell in which the test film is sealed. Water vapordiffusing through the film mixes with the gas in the drychamber and is carried to a pressure-modulated infrared sensor.This sensor measures the fraction of infrare
16、d energy absorbedby the water vapor and produces an electrical signal, theamplitude of which is proportional to water vapor concentra-tion. The amplitude of the electrical signal produced by the testfilm is then compared to the signal produced by measurementof a calibration film of known water vapor
17、 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 is an important property
18、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 conditions, and acceptance
19、 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 acceptable diffusioncell ar
20、ea 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 approximately 6 mm(0.250 in.) has
21、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 thecompressed Oring when
22、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.6.1.1.3 Diffusion Cell A
23、ir 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 chamberpneumatic fittings for the introd
24、uction 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 conditioning rack (Fig. 2)
25、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 specific relative humidity b
26、y 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 modelWVTR instruments that have a
27、 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 wellfor the measurement of tem
28、perature.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 adequate4The sole source of supply of the apparatus kno
29、wn to the committee at this timeis Mocon/Modern Controls, Inc., 7500 Boone Avenue North, Minneapolis, 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 responsib
30、le technical committee,1which you may attend.FIG. 1 Measuring SystemFIG. 2 Conditioning SystemF1249062for this purpose.Athermistor 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 n
31、ecessary to provide cooling coils to removesome of the heat.6.1.4 FlowmeterA means for regulating the flow of dryair within 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.6.1.6 Infrared
32、 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 signal amplifier.6.1.8 Desiccant
33、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 rack and testchamber.6.1.9 Flow-M
34、etering 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 pads of 30to 75 mm in diameter. Nec
35、essary 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 relativehumidities as described in Practice
36、E 104. 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 or other suitable high-vacuum gre
37、ase 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 standardmethods of sampling app
38、licable to the material under test.Sampling may be done in accordance with Practice D 1898.Select samples considered representative of the material to betested. If the material is of nonsymmetrical construction, theorientation should be noted.9. System Calibration With Reference Film9.1 Follow the m
39、anufacturers 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 Specimens TestedTest enough spe
40、cimensto 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 test area and at the center in ac
41、cordance withguidelines described in Test Method D 374.10.3.3 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 lower half-cell and dampen with
42、distilled 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 type of diffusioncell used in
43、 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 the conditioning rack. Allow t
44、he 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 under the test conditions (see
45、 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 after an additional condition
46、inginterval of several hours.5Linde Molecular Sieve, Type 4Aor Type 5A, in the form of18 in. pellets as maybe obtained from the Union Carbide Co., Linde Division, Danbury, CT 06817-0001.FIG. 3 Film Diffusion CellF124906310.5 Record temperature of each test with reference to athermometer or thermocou
47、ple installed in the test chamberthermometer well. Temperature is a critical parameter affectingthe measurement of WVTR. During testing, monitor thetemperature, periodically, to the nearest 0.5C. Report theaverage temperature and the range of temperatures observedduring the test.10.6 Standby and Shu
48、toff Procedures:10.6.1 Follow the manufacturers instructions for puttingthe instrument in standby when not being used.10.6.2 When the system is not to be used for an extendedperiod and there are no films that require conditioning, theelectrical power may be turned off.11. Calculation11.1 WVTRIf usin
49、g 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 relationship:Metric Perms 5WVTRPw5 g/m2day
