1、Designation: D6701 16Standard Test Method forDetermining Water Vapor Transmission Rates ThroughNonwoven and Plastic Barriers1This standard is issued under the fixed designation D6701; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 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 vapor transmission ranging between 5
3、00 to100,000 g/m2day through nonwoven and plastic barrier mate-rials. The method is applicable to films, barriers consisting ofsingle or multilayer synthetic or natural polymers, nonwovenfabric, and nonwoven fabrics coated with films up to 3 mm (0.1in.) in thickness.1.2 This test method provides for
4、 the determination of (1)water vapor transmission rate (WVTR), and (2) the permeanceto water vapor.1.3 The values stated in metric units are to be regarded asthe standard. The acceptable units for water vapor transmissionrate are usually g/m2day.1.4 This standard does not purport to address all of t
5、hesafety 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 determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating
6、to TextilesD1898 Practice for Sampling of Plastics (Withdrawn 1998)3D4204 Practice for Preparing Plastic Film Specimens for aRound-Robin StudyD5729 Test Method for Thickness of Nonwoven Fabrics(Withdrawn 2008)3E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test
7、MethodF1249 Test Method for Water Vapor Transmission RateThrough Plastic Film and Sheeting Using a ModulatedInfrared Sensor3. Terminology3.1 Definitions:3.1.1 water vapor permeability coeffcient, nthe ratio ofthe permeance and the thickness.3.1.1.1 DiscussionThis quantity should not be used unlessth
8、e relationship between thickness and permeance has beenverified in tests using several thickness of the material. Thewater vapor permeability is meaningful only for homogeneousmaterials, in which case it is a property characteristic of bulkmaterial. An accepted unit of water vapor permeability is th
9、emetric perm centimeter, or 1g per m2per day per mm Hg-cm ofthickness. The SI unit is the mol/m2-s-Pa-mm.3.1.2 water vapor permeance, nthe ratio of a barrierswater vapor transmission rate to the vapor pressure differencebetween the two surfaces.3.1.2.1 DiscussionAn accepted unit of water vapor per-m
10、eance is the metric perm, or 1 g/m2per day per mm Hg. TheSI unit is the mol/m2-s-Pa. Since the water vapor permeance ofa specimen is generally a function of relative humidity andtemperature, therefore those conditions must be stated.3.1.3 water vapor transmission rate (WVTR), nthe steady-state time
11、rate of water vapor flow through unit area of aspecimen, normal to the surfaces under specific conditions oftemperature and humidity at each surface.3.1.3.1 DiscussionA common practice accepted unit ofwater vapor transmission rate is metric g/m2per day. The testconditions of relative humidity and te
12、mperature where thedriving force is the difference in relative humidity across thespecimen must be stated.4. Summary of Test Method4.1 A dry chamber, guard film, and a wet chamber make upa diffusion cell in which the test film is sealed. A first test ismade of the water vapor transmission rate of th
13、e guard film andair gap between an evaporator assembly that generates 100 %relative humidity. A sensor produces an electrical signal, the1This test method is under the jurisdiction of ASTM Committee F02 on FlexibleBarrier Packaging and is the direct responsibility of Subcommittee F02.10 onPermeation
14、.Current edition approved Aug. 1, 2016. Published September 2016. Originallyapproved in 2001. Last previous edition approved in 2001 as D670101, which waswithdrawn in October 2008 and reinstated in August 2016.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custo
15、mer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, W
16、est Conshohocken, PA 19428-2959. United States1amplitude of which is proportional to water vapor concentra-tion. The electrical signal is routed to a computer for process-ing. The computer calculates the transmission rate of the airgap and guard film and stores the value for further use. Thebarrier
17、is then sealed in the test cell and the apparatus startedin the test mode. As before, the electrical signal representingthe water vapor is sent to the computer which then calculatesthe transmission rate of the combination of the air gap, theguard film, and the test barrier. The computer then uses th
18、isinformation to calculate the water vapor transmission rate ofthe material being tested. The computer determines when themeasured results indicate that the specimens have reachedequilibrium values and the testing is considered finished.5. Significance and Use5.1 The purpose of this test method is t
19、o obtain values forthe water vapor transmission rate of barrier materials.5.2 Water vapor transmission rate is an important propertyof materials and can be related to shelf life; product stability,breath-ability, and wearing comfort.5.3 Data from this test method is suitable as a refereemethod of te
20、sting, provided that the purchaser and seller haveagreed on sampling procedures, test conditions, and acceptancecriteria.6. Apparatus6.1 This method utilizes water vapor transmission appara-tus4comprised of the following:6.1.1 Test Cells, the apparatus has six test cells within twoassemblies. Fig. 1
21、 shows a typical cell cross section. The sixcells are formed by metal halves which, when closed upon thetest specimens, will accurately define a circular area for each.A typical acceptable diffusion cell area is 10 cm2. The volumeenclosed by each cell half, when clamped, is not critical. It isdesira
22、ble that the air gap between the water evaporatorassembly and the guard film be as small practical, but not sosmall that an unsupported film which sags or buckles willcontact the evaporator assembly. The barrier under test shouldbe in intimate contact with the guard film. A depth ofapproximately 3.2
23、 mm (0.125 in.) has been found to besatisfactory for the carrier gas side of 10-cm2cells.6.1.1.1 Test Cell O-ring, an appropriately sized groovemachined into the humid chamber side of the test cell thatretains a chlorprene O-ring. The test area is considered to be4The sole source of supply of the ap
24、paratus known to the committee at this timeis Mocon, Inc., 7500 Boone Avenue North, Suite 111, Minneapolis, MN 55428. Ifyou are aware of any alternative suppliers, please provide this information toASTMheadquarters. Your comments will receive careful consideration at a meeting of theresponsible tech
25、nical committee, which you may attend. Mocons apparatus isknown as the Permatran-W model 100k.FIG. 1 Typical Cell Cross SectionD6701 162the area established by the inside contact diameter of thecompressed O-ring when the test cell is clamped shut againstthe test specimen.6.1.1.2 Test Cell Sealing Su
26、rface, a flat rim around the dryside of the diffusion cell. This is a critical sealing surfaceagainst which the test specimen is pressed; it shall be smoothand without radial scratches.6.1.1.3 Test Cell Air Passages, two holes in the dry half ofthe diffusion cell that pass carrier gas and water vapo
27、r to eitherexhaust ports or the sensor assembly. One cell at a time can beconnected to the sensor assembly by solenoid valves.6.1.1.4 Test Cell Guard Film, a flat film that covers thehumid side of each cell. The film is a barrier that stills the airin the gap between the water evaporator and the mou
28、ntingplane of the specimen. The guard film is a very high transmitterof water vapor. Its transmission rate as well as that of the airgap is accounted for in the apparatus measurements.6.1.1.5 Water Vapor Sensor, a water vapor detector capableof sensing 0 to 100 % relative humidity with sufficient ac
29、cu-racy so the apparatus can determine transmission rates down to500 g/m2per day.6.1.1.6 Post Sensor Dryer, a no-maintenance dryer thatremoves water vapor from the measurement gas stream after itpasses through the water vapor sensor.6.1.1.7 Mass Flowmeter, a means for regulating the flow ofdry air w
30、ithin an operating range of 0 to 200 cc/min.6.1.1.8 Flow-Metering Valves, fine-metering valves capableof controlling the dry-air flow rate to each test.6.1.2 Computer System, a computer provides the maincontrol, calculating, and data storage device for the system.6.1.3 Temperature Control, Temperatu
31、re of the test speci-men is thermostatically controlled by a Thermo-Electric De-vice (TED) attached to the apparatus that ensures good thermalcontact. A thermistor sensor and an appropriate control circuitwill serve to regulate the temperature from 20 to 50C to within0.1C.6.1.4 Barometric Pressure S
32、ensor, a sensor that measuresthe ambient barometric pressure so that variations are auto-matically corrected in the calculations.7. Reagents and Materials7.1 Desiccant,5for drying air stream.7.2 High Purity Level Chromatograph Grade Distilled Wa-ter (HPLC), for producing 100 % relative humidity.7.3
33、Sealing Grease, a high-viscosity, silicone stopcockgrease or other suitable silicone high-vacuum grease is re-quired for lubrication of O-rings.7.4 Sample Holder, a cardboard or metal sample holder issupplied with the apparatus to facilitate loading of specimens.8. Sampling and Test Specimens8.1 Sel
34、ect material for testing in accordance with standardmethods of sampling applicable to the material under test.Sampling may be done in accordance with Practice D1898 orby 8.2 below.8.2 Selection samples considered representative of the ma-terial to be tested.8.2.1 Primary Sampling UnitConsider rolls,
35、 bolts, orpieces of the flexible barrier material or nonwoven fabric to bethe primary sampling unit, as applicable.8.2.2 Laboratory Sampling UnitAs a laboratory samplingunit, take from the primary sampling unit at least a onefull-width piece that is 1 m (1yd) in length along the (machinedirection, a
36、fter first removinga1m(1yd)length.8.2.2.1 For primary sampling units less than1m(1yd)inlength, use a sufficient number of pieces to prepare the sixspecimens to the size described in 8.2.3.8.2.3 Test Specimen SizeFrom each laboratory-samplingunit, cut at least six test specimens using the template su
37、ppliedwith the apparatus or a similar die cutter. The truncated pieshaped template will produce proper size specimens that coverthe sample cell.8.2.4 Test Specimen SelectionSelect test specimens asfollows:8.2.4.1 Cut specimens representing a broad distributiondiagonally across the width of the labor
38、atory-sampling unit.8.2.4.2 For fabric widths 125 mm (5 in.) or more take nospecimen closer than 25 mm (1 in.) from the selvage edge.8.2.4.3 For fabric widths less than 125 mm (5 in.), use theentire width for specimens.8.2.4.4 Ensure specimens are free of folds, creases, orwrinkles.Avoid getting oil
39、, water, grease, etc. on the specimenswhen handling.9. Conditioning9.1 No pre-conditioning is necessary before starting a test.9.2 Any conditioning of the specimens to the water vapordriving force (differential relative humidity) and temperature iscarried out during the test within the test apparatu
40、s. In general,these materials are high transmitters and the specimens do notrequire a significant conditioning period; they reach equilib-rium in just a few examination periods. (Experience has shownthat individual test periods range from 2 to 10 minutes). Thetime required for sample conditioning va
41、ries as a function ofmany factors such as barrier composition, thickness, testtemperature, etc.10. Preparation of Test Apparatus and Calibration Pre-Test Sample Considerations10.1 Preparation of Apparatus (Fig. 1).10.1.1 If preceding tests have exposed the apparatus to highmoisture levels, outgas th
42、e system to desorb residual moisture.Purge the system with dry air for a period of 3 to 4 hours.10.2 Calibrating the SystemDetermine the transmissionrate of the system including the air gap and the guard film.5Linde Molecular Sieve, Type 4A or Type 5A, in the form of 1/8 in. pellets asmay be obtaine
43、d from the Union Carbide Co., Linde Division, Danbury, CT06817-0001.D6701 163CalC is an acronym for the transmission rate of the apparatushardware, air gap, and guard film without any test specimenspresent.10.2.1 Fill the reservoir with HPLC water.10.2.2 Place a blank six position specimen holder in
44、 thesystem and tighten the clamp.10.2.3 Adjust the gas flow to each cell for uniform RHreading for all cells.10.2.4 Set all cells to CalC.10.2.5 The computer will automatically determine theempty cell transmission rate (CalC) value for each cell.11. Test Procedure11.1 Handle the test specimens caref
45、ully to avoid alteringthe state of the material.11.2 If permeability or permeance are to be calculated afterthe test, measure specimen thickness at four equally spacedpoints within the test area and at the center in accordance withguidelines described in Test Method D5729.11.3 Mount the specimens to
46、 the holder noting the materialidentity in each location. If testing a laminated material, mountthe better barrier portion toward the carrier gas side of the testcell and the poorer barrier toward the guard film.11.4 Because of the type of material that is used for theguard film, grease should not b
47、e used on either the lower cellsealing surface or the upper cell O-ring.11.5 Align the holder over the pins in the bottom portion ofthe cells of the apparatus, place the upper portion of the cellson the base of the apparatus, and then tighten the clamp.11.6 Put the specimens into the test mode via t
48、he computerkeyboard. Enter the global test parameters and individual cellparameters. Place each cell into TEST.11.6.1 Conditioning the SpecimenDuring the setting oftest parameters in the apparatus it is necessary to select tocondition or not condition. Experience has shown that mostmaterials will co
49、ndition in 10 to 20 minutes. Operators oftenchoose to not condition but go directly to test and run an extracycle through the cells.11.6.2 Establish Equilibrium RateAfter the system hascycled through the cells a few times, the measurementsindicate that an equilibrium transmission rate has been reached.This can be determined by manual examination of data or thesystem can be made to stop further testing of each cell by asetup in the computer. When successive values for any cell arewithin 1 %, testing will cease; this is known as convergencemode. In most cases, tw
