ASTM F2622-2008 Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using Various Sensors.pdf

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1、Designation: F 2622 08Standard Test Method forOxygen Gas Transmission Rate Through Plastic Film andSheeting Using Various Sensors1This standard is issued under the fixed designation F 2622; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev

2、ision, 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 a procedure for determinationof the steady-state rate of transmission of o

3、xygen 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 coefficient (PO2) in the

4、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 various sensors,

5、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 as thestandard. The values given in parentheses are for info

6、rmationonly.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 prior to use.2.

7、Referenced Documents2.1 ASTM Standards:2D 1898 Practice for Sampling of Plastics3D 3985 Test Method for Oxygen Gas Transmission RateThrough Plastic Film and Sheeting Using a CoulometricSensor3. Terminology3.1 Definitions:3.1.1 oxygen permeability coeffcient (P8O2)the productof the permeance and the

8、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 verified ontests using several

9、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 SI unit of permeance is the

10、 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 the mol/(m2s). The test cond

11、i-tions, including temperature and oxygen partial pressure onboth sides of the film must be stated.3.1.3.1 DiscussionA commonly used unit of O2GTR isthe cm3(STP)/m2d) at one atmosphere pressure differencewhere 1 cm3(STP) is 44.62 mol, 1 atm is 0.1013 MPa, andone day is 86.4 3 103s. The O2GTR in SI u

12、nits is obtained bymultiplying the value in inch-pound units by 5.160 3 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),relative humidity

13、, 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 contains oxygen. As

14、oxygen gas permeates through1This test 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 April 1, 2008. Published May 2008.2For referenced ASTM standards, visit the ASTM we

15、bsite, 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 Drive, PO Box C700, West Conshohocken, PA 19428-2959

16、, United States.the film into the nitrogen carrier gas, it is transported to thedetector where it produces 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,

17、 the sole determinant, and additional tests, based onexperience, must be used to correlate packaging performancewith O2GTR. It is suitable as a referee method of testing,provided that the purchaser and the seller have agreed onsampling procedures, standardization procedures, test condi-tions, and ac

18、ceptance criteria.5.2 Testing which has compared select instruments withother sensors to the instruments specifically described in TestMethod D 3985 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

19、 non-coulometric andcoulometric sensors.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 carbon mon-oxide, hydrocarbons, free chlorine, and some strong oxidizingag

20、ents. Exposure to carbon dioxide should also be minimizedto avoid damage to the sensor through reaction in some sensortypes.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 ac

21、curatelydefine a circular area. 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 which happens to sag or bulge will contactthe top or bottom of the cell. The diffusion cell shall be

22、provided with a thermometer well for measuring temperature.7.1.1.1 O-RingVarious designs may be included 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 Fittings

23、The diffusioncell shall incorporate suitable fittings for the introduction andexhaust of gases without significant loss or leakage.7.1.1.3 It is desirable to thermostatically control the diffu-sion cell. A simple heating or heating/cooling system regulatedto 60.5C, is adequate for this purpose. A th

24、ermistor sensorand an appropriate control circuit will serve to regulate the celltemperature unless measurements 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-

25、tiple diffusion cells are a practical way to increase the numberof measurements that can be obtained from a 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 ce

26、lls that arenot connected to the sensor. Either test gas or carrier gas, as isappropriate, purges the test 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 permeabili

27、ty in instruments whichcalculate the oxygen permeability based on the oxygen con-centration change in the carrier 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 an

28、d test gas flow streams.7.1.4 SensorAn oxygen-sensitive sensor with sufficientsensitivity and precision to yield meaningful results can usevarious operating principles including coulometric, electro-chemical and zirconium oxide. Different sensors may havedifferent levels of sensitivity. The user sho

29、uld select theinstrument/sensor system which will adequately cover theoxygen permeation range and degree of 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 foundef

30、fective.8. Reagents and Materials8.1 Nitrogen Carrier Gas shall consist of nitrogen. Thecarrier gas shall be 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

31、in this nitrogen to allowcatalysts to function they may be incorporated up to 5 %.8.2 Oxygen Test Gas shall 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

32、 diffusion cell.8.4 Water for HumidificationFor humidification of thecarrier and permeant gas streams, ultra-high purity water isrequired for some instrument types to prevent plugging of thehumidification system. This water should have a resistivity ofat least 18 MV. An example of a suitable type is

33、 high-pressureliquid chromatography (HPLC) water.9. Precautions9.1 Temperature and relative humidity are critical 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 te

34、mperature shall be monitored to the nearest 0.5C and therelative humidity to the nearest 0.5 percent. The averageconditions 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 o

35、f a good barrier afterit has been used to test a poor barrier such as low-densitypolyethylene. For this reason, materials of comparable gastransmission qualities should be tested together.F26220829.3 Back diffusion of air into the unit is undesirable. Careshould therefore be taken to ensure that the

36、re is a flow ofnitrogen through the system at all times. This flow can belowered when the instrument 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 for

37、th).This can be accomplished by the use of the heaters in thediffusion cells.10. Sampling10.1 The sampling units used for the determination ofO2GTR shall be representative of the quantity of product forwhich the data are required, in accordance with PracticeD 1898. Care shall be taken to ensure that

38、 samples arerepresentative of conditions across the width and along thelength of a roll of film.11. 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 thema

39、terial being tested.11.2 Average thickness shall be determined to the nearest2.5 m (0.0001 in.), using 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 spe

40、cimen, it can be doneafter permeation has been tested.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 mountedfac

41、ing the oxygen (test gas) side of the diffusion cell”).12. Conditioning12.1 After the sample has been 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. Proce

42、dure13.1 Various instruments will have somewhat different op-erating procedures and each instruments 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 thesensor

43、and specific system involved some period of timeshould be allowed to insure stability.13.2.2 Diffusion 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, a

44、pply sealing greaseevenly.13.2.3 Specimen PreparationThe size of the specimenobviously depends on 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 g

45、ases to flow topurge the system of ambient air before taking any measure-ments13.3 The following 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 backgr

46、ound oxygen transmissionrate levels are measured first, followed by the measured levelof oxygen transmission 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

47、,if desired, and then to the sensor.13.3.2 Background Diffusion Cell Oxygen TransmissionRateA stream 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

48、rate going through thecarrier side of the cell is measured.13.3.3 Measured Diffusion Cell Oxygen 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 c

49、ell 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 Moist EnvironmentThis test method can beconducted with test and carrier gases at any controlled tem-perature and relative humidity. Provision to control and moni-tor environmental conditions must be made and vali