1、Designation: F1927 14Standard Test Method forDetermination of Oxygen Gas Transmission Rate,Permeability and Permeance at Controlled Relative HumidityThrough Barrier Materials Using a Coulometric Detector1This standard is issued under the fixed designation F1927; the number immediately following the
2、designation indicates the year oforiginal 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
3、procedure for determinationof the rate of transmission of oxygen gas, at steady-state, at agiven temperature and %RH level, through film, sheeting,laminates, co-extrusions, or plastic-coated papers or fabrics.This test method extends the common practice dealing withzero humidity or, at best, an assu
4、med humidity. Humidity playsan important role in the oxygen gas transmission rate (O2GTR)of many materials. This test method provides for the determi-nation of oxygen gas transmission rate (O2GTR), the per-meance of the film to oxygen gas (PO2), the permeationcoefficient of the film to its thickness
5、 (P”O2), and oxygenpermeability coefficient (PO2) in the case of homogeneousmaterials at given temperature and %RH level(s).1.2 The values stated in SI units are to be regarded as thestandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It
6、 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. Specific precau-tionary statements are given in Section 9.2. Referenced Documents2.1 ASTM Standards:2D1898 Practice for Sa
7、mpling of Plastics (Withdrawn 1998)3D3985 Test Method for Oxygen Gas Transmission RateThrough Plastic Film and Sheeting Using a CoulometricSensorE104 Practice for Maintaining Constant Relative Humidityby Means of Aqueous SolutionsE691 Practice for Conducting an Interlaboratory Study toDetermine the
8、Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 oxygen permeability coeffcient (PO2)the product ofthe permeance and the thickness of the film. The permeabilityis meaningful only for homogeneous materials, in which caseit is a property characteristic of the bulk material. This quantitys
9、hould not be used unless the relationship between thicknessand permeance has been verified on tests using several differentthicknesses of the material. The SI unit of oxygen permeabilityis the mol/(msPa). The test conditions (see 3.1.4) must bestated.3.1.2 oxygen permeance (PO2)the ratio of O2GTR to
10、 thedifference between the partial pressure of O2on the two sidesof the film. The SI unit of permeance is the mol/(m2 s Pa).The test conditions (see 3.1.4) must be stated.3.1.3 oxygen permeation coeffcient (P”O2)the ratio ofO2GTR to the thickness of the film. The SI unit of permeanceis the mol/(m2 s
11、 cm). The permeation coefficient is mean-ingful only for homogeneous materials, in which case it is aproperty characteristic of the bulk material. This quantityshould not be used unless the relationship between thicknessand transmission rate is known.3.1.4 oxygen transmission rateat a given temperat
12、ure and%RH (O2GTR), the quantity of oxygen gas passing through aunit area of the parallel surfaces of a plastic film per unit timeunder the conditions of test. The SI unit of transmission rate isthe mol/(m2 s). The test conditions, including temperature,%RH and oxygen partial pressure on both sides
13、of the filmmust be stated.3.1.5 transmission rate (O2GTR)a commonly used metricunit of O2GTR is the cm3(STP)/(m2 d) at one atmospherepressure differential where: 1 cm3at Standard Temperature andPressure (STP = 273.15K; 1.013 105Pa) is 44.62 mol andone day is 86.4 103s. O2GTR in SI units is obtained
14、by1This test method is under the jurisdiction ofASTM Committee F02 on FlexibleBarrier Packaging and is the direct responsibility of Subcommittee F02.10 onPermeation.Current edition approved April 1, 2014. Published June 2014. Originallyapproved in 1998. Last previous edition approved in 2007 as F192
15、7 07. DOI:10.1520/F1927-14.2For 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.3The last approved version of this
16、 historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1multiplying the value in metric units by 5.165 10-10or thevalue in inch-pound units (cm3(STP)/100 in.2 d) by8.005 10-9.4. Summary of Tes
17、t Method4.1 The oxygen gas transmission rate is determined after thesample has equilibrated in a given temperature and humidityenvironment.4.2 The specimen is mounted as a sealed semi-barrierbetween two chambers at ambient atmospheric pressure. Onechamber is slowly purged by a stream of nitrogen at
18、a giventemperature and %RH and the other chamber is purged by astream of oxygen at the same temperature as the N2stream butmay have a different %RH than the N2stream. In this case theenvironment would more closely simulate actual shelf condi-tions. As oxygen gas permeates through the film into theni
19、trogen carrier gas, it is transported to the coulometricdetector where it produces an electrical current, the magnitudeof which is proportional to the amount of oxygen flowing intothe detector per unit time.5. Significance and Use5.1 O2GTR at a given temperature and %RH is an importantdeterminant of
20、 the packaging protection afforded by barriermaterials. It is not, however the sole determinant, and addi-tional tests, based on experience, must be used to correlatepackaging performance with O2GTR. It is suitable as a refereemethod of testing, provided that purchaser and seller haveagreed on sampl
21、ing procedures, standardization procedures,test conditions and acceptance criteria.6. Interferences6.1 The presence of certain interfering substances in thecarrier gas stream may give rise to unwanted electrical outputsand error factors. Interfering substances include free chlorineand some strong ox
22、idizing agents. Exposure to carbon dioxideshould also be minimized to avoid damage to the sensorthrough reaction with the potassium hydroxide electrolyte.7. Apparatus7.1 Oxygen Gas Transmission Apparatus, as diagramed inFig. 1 and described following. Alternative systems need to beevaluated to ensur
23、e equivalent performance.7.1.1 Diffusion Cell, consisting of two metal halves, that,when closed upon the test specimen, will accurately define acircular area. Typical acceptable diffusion cell areas are 100and 50 cm2. The volume enclosed by each cell half, whenclamped, is not critical: it should be
24、small enough to allow forrapid gas exchange, but not so small that an unsupported filmwhich happens to sag or bulge will contact the sides of the cell.The diffusion cell shall be provided with a temperaturemeasuring and controlling capability and a means to measureand control relative humidity.7.1.1
25、.1 Temperature control is critical because RH can varyas much as 5 % RH/C in certain temperature regions. Acompact design of the diffusion cell structure with associatedcontrols would lend itself to better temperature control. Thetemperature should be controlled to 60.5C or better.7.1.1.2 O-RingAn a
26、ppropriately sized groove, machinedinto the oxygen (or test gas) side of the diffusion cell, retains aneoprene O-ring. The test area is considered to be that areaFIG. 1 A Practical Arrangement of Components for the Measurement of Oxygen Transmission Rate Under Precise Relative HumidityConditions Usi
27、ng the Coulometric MethodF1927 142established by the inside contact diameter of the compressedO-ring when the diffusion cell is clamped shut against the testspecimen. The area,A, can be obtained by measuring the insidediameter of the imprint left by the O-ring on the specimen afterit has been remove
28、d from the diffusion cell.7.1.1.3 The nitrogen (or carrier gas) side of the diffusion cellshall have a flat raised rim. Since this rim is a critical sealingsurface against which the test specimen is pressed, it shall besmooth and flat, without radial scratches.7.1.1.4 Diffusion Cell Pneumatic Fittin
29、gsEach half of thediffusion cell shall incorporate suitable fittings for the intro-duction and exhaust of gasses without significant loss orleakage.7.1.1.5 Experience has shown that arrangements using mul-tiple diffusion cells are a practical way to increase the numberof measurements which can be ob
30、tained from a coulometricsensor. A valving manifold shall connect the carrier gas side ofeach individual diffusion cell to the sensor in a preselectedpattern. Carrier gas is continually purging the carrier gas sidesof those cells that are not connected to the sensor. Either testgas or carrier gas, a
31、s is appropriate, purges the test gas chamberof any individual cell.7.1.2 Catalyst BedShould be used on the carrier gas (N2)side of the diffusion cell assembly to provide an essentiallyoxygen free carrier gas. Palladium catalyst on alumina convertsO2molecules into H2O, thus virtually eliminating O2m
32、ol-ecules in the carrier gas.7.1.3 Oxygen gas transmission apparatus shall have thecapability of measuring, at a variety of relative levelsincluding, zero RH to 90 % RH at a wide range of tempera-tures.7.1.4 Package testing at given temperature and %RH levelsto be optional if it is not included in t
33、he basic configuration.7.1.5 Coulometric SensorAn oxygen-sensitive coulomet-ric sensor operating at an essentially constant efficiency shallbe used to monitor the quantity of oxygen transmitted.7.1.6 With computer controlled systems, the results areprinted out giving final results, time-history of e
34、quilibration,ambient conditions of test, material being tested and date.Should a failure occur, the time of this occurrence and its causeand correction taken should be documented for operatoranalysis as to the validity of continued testing.7.1.7 RH DetectorsWater sensitive solid-state devices areuse
35、d to monitor the relative humidity of the gases directly inthe upper and lower halves of the cell.7.1.7.1 Placement of the RH detectors in the diffusion cellsis important because relative humidity will change wheneverthe temperature of the relative humidity source and diffusioncells differ.7.1.7.2 T
36、he RH detectors should periodically be calibratedagainst saturated salt solutions (see Practice E104) or NISTtraceable devices.48. Reagents and Materials8.1 Nitrogen Carrier Gas, consisting of a nitrogen andhydrogen mixture in which the percentage of hydrogen shallfall between 0.5 and 3.0 volume %.
37、The carrier gas shall be dryand contain not more than 100 ppm of oxygen.Acommerciallyavailable mixture known as “forming gas” is suitable.8.2 Oxygen Test Gas, shall be dry and contain not less than99.5 % oxygen (except as provided in 14.10).8.3 Water to Generate %RHDouble or triple-distilledwater is
38、 recommended (not deionized water) for preciserelative humidity generation and to avoid scale build up.8.4 Sealing GreaseA high-viscosity hydrocarbon grease5(preferred) or a high-vacuum grease is required for sealing thespecimen film in the diffusion cell.9. Precautions9.1 Temperature is a critical
39、parameter affecting the mea-surement of O2GTR. Careful temperature control will help tominimize variations due to temperature fluctuations. Duringequilibration and testing the temperature shall be monitoredperiodically. Should this temperature exceed 60.5C afterreaching the desired temperature, repo
40、rt the average tempera-ture and the range of temperatures found during the test.9.2 The sensor will require a relatively long time to stabilizeto a low reading characteristic of a good barrier after it hasbeen used to test a poorer barrier such as low densitypolyethylene. For this reason, materials
41、of comparable gastransmission qualities should be tested together.9.3 Back diffusion of air into the unit is undesirable. Careshould be taken to ensure that there is a flow of nitrogenthrough the system at all times. This flow can be low when theinstrument is not being used.9.4 Elevated temperatures
42、 to hasten specimen out gassing isnot recommended. RH is a function of temperature and,therefore, equilibrating at some other temperature than the testtemperature would expose the sample to an incorrect RHduring the equilibration process. The entire test should be runat constant temperature and cons
43、tant RH.10. Sampling10.1 The samples used for the determination of O2GTRshall be representative of the quality of product for which thedata are required, in accordance with Practice D1898.5Careshall be taken to ensure that film samples are representative ofconditions across the width and along the l
44、ength of the filmbeing tested.11. Test Specimen11.1 Test specimens shall be representative of the materialbeing tested and free of defects, including wrinkles, creases,and pinholes, unless these are a characteristic of the materialbeing tested.11.2 Average thickness shall be determined to the neares
45、t2.5 m (0.0001 in.), using a calibrated dial gage or equivalent4Hasegawa, S. (NIST) “National Basis of Accuracy in HumidityMeasurements,” ISA Transactions, Vol 25, No. 3, 1986, pp. 1524.5A suitable hydrocarbon grease such as Apiezon T is known to the committee atthis time. If you are aware of altern
46、ative suppliers, please provide this informationto ASTM Headquarters. Your comments will receive careful consideration at ameeting of the responsible technical committee that you may attend.F1927 143at a minimum of five points distributed over the entire test area.Maximum, minimum, and average value
47、s shall be recorded.11.3 If the test specimen is of an asymmetrical construction,the two surfaces shall be marked by appropriate distinguishingmarks and the orientation of the test specimen in the diffusioncell shall be reported (for example, “Side II Was MountedFacing the Oxygen Side of the Diffusi
48、on Cells”).12. Calibration12.1 General ApproachThe oxygen detector used in thistest method is a coulometric device that yields a linear outputas predicted by Faradays Law. In principle, four electrons areproduced by the detector for each molecule of oxygen thatpasses into it. Considering that the de
49、tector is known to have abasic efficiency of 95 to 98 % it may be considered an“intrinsic” standard.12.1.1 Experience has shown, however, that under somecircumstances the sensor may become depleted or damaged tothe extent that efficiency and response are impaired. For thisreason, this test method incorporates means for periodicdetector evaluation. This evaluation is derived from measure-ments of a known-value “Reference Package”.12.2 Detector EvaluationThe reference package is a dif-fusion cell in which a sheet of reference of known O2
