1、Designation: F 1927 07Standard 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 F 1927; the number immediately following th
2、e 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers
3、 a 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 a
4、ssumed 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 (P8O2), the permeationcoefficient of the film to its thick
5、ness (PO2), and oxygenpermeability coefficient (P9O2) 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
6、. 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. Specific precau-tionary statements are given in Section 9.2. Referenced Documents2.1 ASTM Standards:2D 1898 Practice f
7、or Sampling of Plastics3D 3985 Test Method for Oxygen Gas Transmission RateThrough Plastic Film and Sheeting Using a CoulometricSensorE 104 Practice for Maintaining Constant Relative Humidityby Means of Aqueous SolutionsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision
8、 of a Test Method3. Terminology3.1 Definitions:3.1.1 oxygen permeability coeffcient (P9O2)the productof the permeance and the thickness of the film. The permeabil-ity is meaningful only for homogeneous materials, in whichcase it is a property characteristic of the bulk material. Thisquantity should
9、not be used unless the relationship betweenthickness and permeance has been verified on tests usingseveral different thicknesses of the material. The SI unit ofoxygen permeability is the mol/msPa.Thetest conditions(see 3.1.4) must be stated.3.1.2 oxygen permeance (P8O2)the ratio of O2GTR to thediffe
10、rence between the partial pressure of O2on the two sidesof the film. The SI unit of permeance is the mol/m2 s Pa. Thetest conditions (see 3.1.4) must be stated.3.1.3 oxygen permeation coeffcient (PO2)the ratio ofO2GTR to the thickness of the film. The SI unit of permeanceis the mol/m2 s cm. The perm
11、eation coefficient is meaningfulonly for homogeneous materials, in which case it is a propertycharacteristic of the bulk material. This quantity should not beused unless the relationship between thickness and transmis-sion rate is known.3.1.4 oxygen transmission rateat a given temperature and%RH (O2
12、GTR), 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 of the filmmust
13、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 cm3(STP) is 44.62 mol, 1 atm is0.1013 MPa, and one day is 86.4 3 103s. O2GTR in SI unitsis obtained by multiplying the value in metric units by1This test
14、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, 2007. Published August 2007. Originallyapproved in 1998. Last previous edition approved in 2004 as F 1927 98 (2004
15、).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 Barr Harbor D
16、rive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.165 3 10-10or the value in inch-pound units (cm3/STP/100in.2 d) by 8.005 3 10-9.4. Summary of Test Method4.1 The oxygen gas transmission rate is determined after thesample has equilibrated in a given temperature and humidityenviron
17、ment.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 a giventemperature and %RH and the other chamber is purged by astream of oxygen at the same temperature as the N2stream butmay have a
18、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 thenitrogen carrier gas, it is transported to the coulometricdetector where it produces an electrical current, the magnitudeof which is pro
19、portional 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 the packaging protection afforded by barriermaterials. It is not, however the sole determinant, and addi-tional tests, based on exper
20、ience, must be used to correlatepackaging performance with O2GTR. It is suitable as a refereemethod of testing, provided that purchaser and seller haveagreed on sampling procedures, standardization procedures,test conditions and acceptance criteria.6. Interferences6.1 The presence of certain interfe
21、ring substances in thecarrier gas stream may give rise to unwanted electrical outputsand error factors. Interfering substances include free chlorineand some strong oxidizing agents. Exposure to carbon dioxideshould also be minimized to avoid damage to the sensorthrough reaction with the potassium hy
22、droxide electrolyte.7. Apparatus7.1 Oxygen Gas Transmission Apparatus, as diagramed inFig. 1 and described following. Alternative systems need to beevaluated to ensure equivalent performance.7.1.1 Diffusion Cell, consisting of two metal halves, that,when closed upon the test specimen, will accuratel
23、y 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 small enough to allow forrapid gas exchange, but not so small that an unsupported filmwhich happens to sag or bulge will contact the s
24、ides of the cell.The diffusion cell shall be provided with a temperaturemeasuring and controlling capability and a means to measureand control relative humidity.7.1.1.1 Temperature control is critical because RH can varyas much as 5 % RH/C in certain temperature regions. Acompact design of the diffu
25、sion 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 appropriately sized groove, machinedinto the oxygen (or test gas) side of the diffusion cell, retains aneoprene O-ring. The test area i
26、s considered to be that areaFIG. 1 A Practical Arrangement of Components for the Measurement of Oxygen Transmission Rate Under Precise Relative HumidityConditions Using the Coulometric MethodF 1927 072established by the inside contact diameter of the compressedO-ring when the diffusion cell is clamp
27、ed 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 removed 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 ri
28、m 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 FittingsEach half of thediffusion cell shall incorporate suitable fittings for the intro-duction and exhaust of gasses without significant
29、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 obtained from a coulometricsensor. A valving manifold shall connect the carrier gas side ofeach individual diffusion cell to the sensor
30、 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, as is appropriate, purges the test gas chamberof any individual cell.7.1.2 Catalyst BedShould be used on the carrier gas (N2)side of t
31、he diffusion cell assembly to provide an essentiallyoxygen free carrier gas. Palladium catalyst on alumina4con-verts O2molecules into H2O, thus virtually eliminating O2molecules in the carrier gas.7.1.3 Oxygen gas transmission apparatus5shall have thecapability of measuring, at a variety of relative
32、 levels includ-ing, zero RH to 90 % RH at a wide range of temperatures.7.1.4 Package testing at given temperature and %RH levelsto be optional if it is not included in the basic configuration.7.1.5 Coulometric SensorAn oxygen-sensitive coulomet-ric sensor operating at an essentially constant efficie
33、ncy shallbe used to monitor the quantity of oxygen transmitted.57.1.6 With computer controlled systems, the results areprinted out giving final results, time-history of equilibration,ambient conditions of test, material being tested and date.Should a failure occur, the time of this occurrence and it
34、s causeand correction taken should be documented for operatoranalysis as to the validity of continued testing.7.1.7 RH DetectorsWater sensitive solid-state devices areused 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 dete
35、ctors in the diffusion cellsis important because relative humidity will change wheneverthe temperature of the relative humidity source and diffusioncells differ.7.1.7.2 The RH detectors should periodically be calibratedagainst saturated salt solutions (see Practice E 104) or NISTtraceable devices.68
36、. 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 %. The carrier gas shall be dryand contain not more than 100 ppm of oxygen.Acommerciallyavailable mixture known as “forming gas” is
37、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 recommended (not deionized water) for preciserelative humidity generation and to avoid scale build up.8.4 Sealing GreaseA high-v
38、iscosity hydrocarbon grease7(preferred) or a high-vacuum grease is required for sealing thespecimen film in the diffusion cell.9. Precautions9.1 Temperature is a critical parameter affecting the mea-surement of O2GTR. Careful temperature control will help tominimize variations due to temperature flu
39、ctuations. Duringequilibration and testing the temperature shall be monitoredperiodically. Should this temperature exceed 60.5C afterreaching the desired temperature, report the average tempera-ture and the range of temperatures found during the test.9.2 The sensor will require a relatively long tim
40、e 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 of comparable gastransmission qualities should be tested together.9.3 Back diffusion of air into the unit is undesirable. Caresho
41、uld 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 to hasten specimen out gassing isnot recommended. RH is a function of temperature and,therefore, equilibrating at some other tem
42、perature than the testtemperature would expose the sample to an incorrect RHduring the equilibration process. The entire test should be runat constant temperature and constant RH.10. Sampling10.1 The samples used for the determination of O2GTRshall be representative of the quality of product for whi
43、ch the4The sole source of supply of the apparatus, a suitable catalyst, known to thecommittee at this time is Englehard Industries Division, Chemical Department, 429Delancey Street, Newark, NJ 07105. If you are aware of alternative suppliers, pleaseprovide this information to ASTM Headquarters. Your
44、 comments will receivecareful consideration at a meeting of the responsible technical committee that youmay attend.5The sole source of supply of suitable apparatus such as that embodied in severallater OX-TRAN models known to the committee at this time is available fromMOCON/Modern Controls, Inc. 75
45、00 Boone Ave N, Minneapolis, MN 55428. Ifyou are aware of alternative suppliers, please provide this information to ASTMHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee that you may attend.6Hasegawa, S. (NIST) “National Basis of Accura
46、cy in Humidity Measure-ments,” ISA Transactions, Vol 25, No. 3, 1986, pp. 1524.7The sole source of supply of the apparatus, a suitable hydrocarbon grease suchas Apiezon T, known to the committee at this time is, Biddle Instruments, 510Township Road, Blue Bell, PA 19422. If you are aware of alternati
47、ve suppliers,please provide this information toASTM Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee that youmay attend.F 1927 073data are required, in accordance with Practice D 1898.7Careshall be taken to ensure that film samples are
48、 representative ofconditions across the width and along the length 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 te
49、sted.11.2 Average thickness shall be determined to the nearest2.5 m (0.0001 in.), using a calibrated dial gage or equivalentat a minimum of five points distributed over the entire test area.Maximum, minimum, and average values 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 Diffusion Cells”).12. Calibration12.1
