1、Designation: F2622 08 (Reapproved 2013)Standard Test Method forOxygen Gas Transmission Rate Through Plastic Film andSheeting Using Various Sensors1This standard is issued under the fixed designation F2622; the number immediately following the designation indicates the year oforiginal adoption or, in
2、 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 determinationof the steady-state rate of tr
3、ansmission of oxygen gas throughplastics in the form of film, sheeting, laminates, coextrusions,or plastic-coated papers or fabrics. It provides for the determi-nation of (1) oxygen gas transmission rate (O2GTR), (2) thepermeance of the film to oxygen gas (PO2), and (3) oxygenpermeability coefficien
4、t (PO2) in the case of homogeneousmaterials.1.2 This test method does not purport to be the only methodfor measurement of O2GTR. There may be other methods ofO2GTR determination that use other oxygen sensors andprocedures.1.3 This test method has intentionally been prepared toallow for the use of va
5、rious sensors, devices, and procedures.The precision and bias of each design needs to be individuallyestablished to determine the applicability of that instrument ormethod to meet the needs of the user.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are
6、 included in thisstandard.1.5 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 determine the applica-bility of regulatory limitations pr
7、ior to use.2. Referenced Documents2.1 ASTM Standards:2D1898 Practice for Sampling of Plastics (Withdrawn 1998)3D3985 Test Method for Oxygen Gas Transmission RateThrough Plastic Film and Sheeting Using a CoulometricSensor3. Terminology3.1 Definitions:3.1.1 oxygen permeability coeffcient (PO2)the prod
8、uct ofthe permeance and the thickness of film. The permeability ismeaningful only for homogeneous materials, in which case it isa property characteristic of the bulk material. The oxygenpermeability coefficient should not be used, unless the relation-ship between thickness and permeance has been ver
9、ified ontests using several different thicknesses of the material. The SIunit of oxygen permeability is the mol/(msPa). The testconditions (see 3.1.3) must be stated.3.1.2 oxygen permeance (PO2)the ratio of the O2GTR tothe difference between the partial pressure of O2on the twosides of the film.The
10、SI unit of permeance is the mol/(m2sPa).The test conditions (see 15.1) must be stated.3.1.3 oxygen transmission rate (O2GTR)the quantity ofoxygen gas passing through a unit area of the parallel surfacesof a plastic film per unit time under the conditions of test. TheSI unit of transmission rate is t
11、he mol/(m2s). The testconditions, including temperature and oxygen partial pressureon both sides of the film must be stated.3.1.3.1 DiscussionAcommonly used unit of O2GTR is thecm3(STP)/m2d) at one atmosphere pressure difference where1cm3(STP) is 44.62 mol, 1 atm is 0.1013 MPa, and one dayis 86.4 10
12、3s. The O2GTR in SI units is obtained bymultiplying the value in inch-pound units by 5.160 10-10.4. Summary of Test Method4.1 The oxygen gas transmission rate is determined after thesample has equilibrated in a controlled test environment.Control of carrier gas flow rate (for concentration detectors
13、),relative humidity, temperature, and oxygen concentration inboth the carrier gas and permeant (test) gas chambers iscritical.4.2 The specimen is mounted as a sealed semi-barrierbetween two chambers at ambient atmospheric pressure. Astream of nitrogen slowly purges one chamber and the otherchamber c
14、ontains oxygen. As oxygen gas permeates through1This 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 Oct. 1, 2013. Published November 2013. Originallyapproved in 2008
15、. Last previous edition approved in 2008 as F2622 08. DOI:10.1520/F2622-08R13.2For 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 on
16、the 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, West Conshohocken, PA 19428-2959. United States1the film into the nitrogen carrier gas, it is transported to thedetector where it pro
17、duces a signal representing the oxygentransmission rate.5. Significance and Use5.1 The O2GTR is an important determinant of the pack-aging protection afforded by barrier materials. It is not,however, the sole determinant, and additional tests, based onexperience, must be used to correlate packaging
18、performancewith O2GTR. It is suitable as a referee method of testing,provided that the purchaser and the seller have agreed onsampling procedures, standardization procedures, testconditions, and acceptance criteria.5.2 Testing which has compared select instruments withother sensors to the instrument
19、s specifically described in TestMethod D3985 is shown in Section 16, Precision and Bias, ofthis method.5.3 The Precision and Bias section of this method showsresults using several instruments with non-coulometric andcoulometric sensors.6. Interferences6.1 The presence of certain interfering substanc
20、es in thecarrier gas stream may give rise to unwanted electrical outputsand error factors. Interfering substances include carbonmonoxide, hydrocarbons, free chlorine, and some strong oxi-dizing agents. Exposure to carbon dioxide should also beminimized to avoid damage to the sensor through reaction
21、insome sensor types.7. Apparatus7.1 Oxygen Gas Transmission Apparatus, with the follow-ing:7.1.1 Diffusion Cell shall consist of two metal halves,which, when closed upon the test specimen, will accuratelydefine a circular area. The volume enclosed by each cell half,when clamped, is not critical; it
22、should be small enough toallow for rapid gas exchange, but not so small that anunsupported film which happens to sag or bulge will contactthe top or bottom of the cell. The diffusion cell shall beprovided with a thermometer well for measuring temperature.7.1.1.1 O-RingVarious designs may be included
23、 in thediffusion cell design. Some systems may require vacuumgrease to form a proper seal.The design will define the test areaof the film as it is tested.7.1.1.2 Diffusion Cell Pneumatic FittingsThe diffusioncell shall incorporate suitable fittings for the introduction andexhaust of gases without si
24、gnificant loss or leakage.7.1.1.3 It is desirable to thermostatically control the diffu-sion cell.Asimple heating or heating/cooling system regulatedto 60.5C, is adequate for this purpose. A thermistor sensorand an appropriate control circuit will serve to regulate the celltemperature unless measure
25、ments are being made close toambient temperature. In this case, it is desirable to providecooling capability to remove some of the heat.7.1.1.4 Experience has shown that arrangements using mul-tiple diffusion cells are a practical way to increase the numberof measurements that can be obtained from a
26、 single sensor.Valves connect the carrier gas side of each individual diffusioncell to the sensor in a predetermined pattern. Carrier gas iscontinually purging the carrier gas sides of those cells that arenot connected to the sensor. Either test gas or carrier gas, as isappropriate, purges the test
27、gas chamber of any individual cell.7.1.2 Flow ControllerA flow controller will control theflow of carrier and test gases with sufficient precision to allowdetermination of the oxygen permeability in instruments whichcalculate the oxygen permeability based on the oxygen con-centration change in the c
28、arrier gas stream. In some instru-ments (such as the Coulometric), the flow rate does not need tobe controlled as precisely.7.1.3 Flow Switching ValvesValves for the switching ofthe nitrogen and test gas flow streams.7.1.4 SensorAn oxygen-sensitive sensor with sufficientsensitivity and precision to
29、yield meaningful results can usevarious operating principles including coulometric, electro-chemical and zirconium oxide. Different sensors may havedifferent levels of sensitivity. The user should select theinstrument/sensor system which will adequately cover theoxygen permeation range and degree of
30、 precision of interest.7.1.5 Data Recording SystemAn appropriate data record-ing system shall record all pertinent information. Variousintegrated and external computer systems have been foundeffective.8. Reagents and Materials8.1 Nitrogen Carrier Gas shall consist of nitrogen. Thecarrier gas shall b
31、e dry and contain not more than 5 ppm ofoxygen. If catalysts or other oxygen absorbers are employed, ahigher oxygen level may be found to be acceptable. If othergases are needed to be included in this nitrogen to allowcatalysts to function they may be incorporated up to 5 %.8.2 Oxygen Test Gas shall
32、 be dry and contain not less than99 % oxygen (except as provided in 13.8).8.3 Sealing GreaseFor some instrument types, a vacuumor stopcock grease may be required to seal the specimen filmin the diffusion cell.8.4 Water for HumidificationFor humidification of thecarrier and permeant gas streams, ultr
33、a-high purity water isrequired for some instrument types to prevent plugging of thehumidification system. This water should have a resistivity ofat least 18 M. An example of a suitable type is high-pressureliquid chromatography (HPLC) water.9. Precautions9.1 Temperature and relative humidity are cri
34、tical param-eters affecting the measurement of O2GTR. Careful tempera-ture and relative humidity control can help to minimizevariations due to environmental fluctuations. During testing,the temperature shall be monitored to the nearest 0.5C and therelative humidity to the nearest 0.5 percent. The av
35、erageconditions and range of conditions experienced during the testperiod shall both be reported.9.2 The sensor may require a relatively long time tostabilize to a low reading characteristic of a good barrier afterit has been used to test a poor barrier such as low-densityF2622 08 (2013)2polyethylen
36、e. For this reason, materials of comparable gastransmission qualities should be tested together.9.3 Back diffusion of air into the unit is undesirable. Careshould therefore be taken to ensure that there is a flow ofnitrogen through the system at all times. This flow can belowered when the instrument
37、 is not being used.9.4 Elevated temperatures can be used to hasten specimenoutgassing, provided that the treatment does not alter the basicstructure of the specimen (crystallinity, density, and so forth).This can be accomplished by the use of the heaters in thediffusion cells.10. Sampling10.1 The sa
38、mpling units used for the determination ofO2GTR shall be representative of the quantity of product forwhich the data are required, in accordance with PracticeD1898. Care shall be taken to ensure that samples are repre-sentative of conditions across the width and along the length ofa roll of film.11.
39、 Test Specimens11.1 Test specimens shall be representative of the materialbeing tested and shall be free of defects, including wrinkles,creases, and pinholes, unless these are a characteristic of thematerial being tested.11.2 Average thickness shall be determined to the nearest2.5 m (0.0001 in.), us
40、ing a calibrated dial gage (or equivalent)at a minimum of five points distributed over the entire test area.Maximum, minimum, and average values shall be recorded. Ifthis measurement may damage the specimen, it can be doneafter permeation has been tested.11.3 If the test specimen is of an asymmetric
41、al 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 (test gas) side of the diffusion cell”).12. Conditioning12.1 After the sample has be
42、en mounted in the diffusioncell, a sufficient length of time must be allowed for the film toreach equilibrium. No conditioning prior to mounting the filmsample in the diffusion cell is needed.13. Procedure13.1 Various instruments will have somewhat different op-erating procedures and each instrument
43、s specifics are beyondthe scope of this test method.13.2 Regardless of the specific instrument employed, thereare some steps common to any system.13.2.1 Instrument Warm-Up PeriodDepending on the sen-sor and specific system involved some period of time should beallowed to insure stability.13.2.2 Diff
44、usion Cell PreparationIn many systems, theseal separating the test area of the film and the surroundingenvironment requires O-rings or finished surfaces. If recom-mended by the instrument manufacturer, apply sealing greaseevenly.13.2.3 Specimen PreparationThe size of the specimenobviously depends on
45、 the diffusion cell design. The sample isplaced carefully in the diffusion cell taking care to avoidwrinkles and creases. Clamp the halves of the cell togethertightly.13.2.4 Purging the SystemAllow the gases to flow topurge the system of ambient air before taking any measure-ments13.3 The following
46、three flow alternative configurations forthe carrier gas are made using various valves and controls. Theoxygen transmission rate in the carrier gas is measured in eachconfiguration. Typically, the background oxygen transmissionrate levels are measured first, followed by the measured levelof oxygen t
47、ransmission rate through the film.13.3.1 Background Gas Cylinder Oxygen TransmissionRateThe gas is flowed directly from the carrier gas source,through an oxygen reducing catalyst or other oxygen absorber,if desired, and then to the sensor.13.3.2 Background Diffusion Cell Oxygen TransmissionRateA str
48、eam of carrier gas is directed through the upper(test gas) side of the diffusion cell) and another stream flowsthrough the lower (carrier gas) side of the diffusion cellchambers. The oxygen transmission rate going through thecarrier side of the cell is measured.13.3.3 Measured Diffusion Cell Oxygen
49、TransmissionRateThe carrier gas is directed to flow through the carrierside of the cell while oxygen (in whatever concentration isdesired) is directed through the oxygen (test gas) side of thediffusion cell and then to the sensor.13.4 Temperature shall be obtained by monitoring the tem-perature as closely as possible to the specimen.13.5 Standby and Shutoff ProceduresFollow the manufac-turers instructions in the instrument manual for putting theinstrument into standby mode when the system will not be usedfor an extended period.13.6 Tests in a
