1、Designation: F 1307 02 (Reapproved 2007)Standard Test Method forOxygen Transmission Rate Through Dry Packages Using aCoulometric Sensor1This standard is issued under the fixed designation F 1307; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、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 a procedure for the determina-tion of the steady-state rate of trans
3、mission of oxygen gas intopackages. More specifically, the method is applicable topackages that in normal use will enclose a dry environment.1.2 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
4、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:2D 1434 Test Method for Determining Gas PermeabilityCharacteristics of Plastic Film and SheetingD 1898 Practice for Sampling of Plas
5、tics3D 3985 Test Method for Oxygen Gas Transmission RateThrough Plastic Film and Sheeting Using a CoulometricSensorE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 oxygen gas transm
6、ission rate (O2GTR)as applied toa package, is the quantity of oxygen gas passing through thesurface of the package per unit of time.3.1.1.1 DiscussionThe SI unit of transmission rate is themol/pkgs. The test conditions, including temperature, oxygenpartial pressure and humidity on both sides of the
7、package,must be stated. A commonly used unit of O2GTR is thecm3(STP)/pkgd, where 1 cm3(STP) is 44.62 3 106mol, 1atm is 0.1013 mPa, and one day is 86 400 s.3.1.2 oxygen permeability coeffcient (PO29)the productof the permeance and thickness of the barrier.3.1.2.1 DiscussionThe permeability is meaning
8、ful onlyfor homogenous materials, in which case it is a propertycharacteristic of the bulk material. This quantity should not beused unless the relationship between thickness and permeancehas been verified in tests using several thicknesses of thematerial.The SI unit of permeability is the mol/msPa.
9、The testconditions must be stated.3.1.3 oxygen permeance (PO28)the ratio of the O2GTR tothe difference between the partial pressure of O2on the twosides of the package wall.3.1.3.1 DiscussionThe SI unit of permeance is the mol/(pkgsPa). The test conditions (see 4.2) must be stated.4. Summary of Test
10、 Method4.1 This test method employs a coulometric oxygen sensorand associated equipment in an arrangement similar to thatdescribed in Test Method D 3985. Oxygen gas transmissionrate (O2GTR) is determined after the package has beenmounted on a test fixture and has equilibrated in the testenvironment.
11、4.2 The package is mounted in such a way as to provide thatthe inside of the package is slowly purged by a stream ofnitrogen while the outside of the package is exposed to aknown concentration of oxygen. The package may be exposedin ambient room air which contains 20.8 % oxygen, or im-mersed in an a
12、tmosphere of 100 % oxygen. As oxygen perme-ates through the package walls into the nitrogen carrier gas, itis transported to the coulometric detector where it produces anelectrical current, the magnitude of which is proportional to theamount of oxygen flowing into the detector per unit of time.5. Si
13、gnificance and Use5.1 Oxygen gas transmission rate is an important determi-nant of the protection afforded by barrier materials. It is not,however, the sole determinant, and additional tests, based onexperience, must be used to correlate package performancewith O2GTR. This test method is suitable as
14、 a referee methodof testing, provided that the user and source have agreed on1This 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 May 1, 2007. Published June 2007. O
15、riginallyapproved in 1990. Last previous edition approved in 2002 as F 1307 02.2For 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 o
16、nthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.sampling procedures, standardization procedures, test condi-tions, and acceptance criteria.6. Interferences6.1 The presence of certain interfering substance
17、s 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 hydroxide electr
18、olyte.7. Apparatus7.1 Oxygen Gas Transmission Apparatus,4as diagrammedin Fig. 1 with the following:7.1.1 Package Test Stations, providing a means for theintroduction and exhaust of the nitrogen carrier gas streamwithout significant loss or leakage.7.1.1.1 Experience has shown that arrangements using
19、 mul-tiple package test stations are a practical way to increase thenumber of measurements that can be obtained from a coulo-metric sensor. A valving manifold connects the carrier gas sideof each individual test station to the sensor in a predeterminedpattern. Carrier gas is continually purging the
20、carrier gas sidesof those packages that are not connected to the sensor. Eithertest gas (100 % oxygen) or normal room air (20.8 % oxygen),whichever is appropriate, contacts the outside of the package.7.1.2 Diffusion Cell, consisting of two metal halves which,when closed upon the film used for system
21、 calibration, willaccurately define a circular area of that film. Typical diffusioncell areas are 100 cm2and 30 cm2. The volumes inside the cellabove and below the enclosed film are not critical; they shouldbe small enough to allow for rapid gas exchange, but not sosmall that an unsupported film whi
22、ch happens to sag or bulgewill contact the top or bottom of the cell. Means shall beprovided for the measurement of cell temperature.7.1.2.1 O-RingAn appropriately sized groove, machinedinto the oxygen (or test gas) side of the diffusion cell, retains aneoprene O-ring. The test area is considered to
23、 be the areaestablished 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 removed from the diffusion
24、cell.7.1.2.2 The nitrogen (or carrier gas) side of the diffusion cellshall have a flat raised rim. Since this rim is the sealing surfaceagainst which the test specimen is pressed, it must be smoothand flat, without scratches which may promote leakage.7.1.2.3 Diffusion Cell Pneumatic FittingsEach hal
25、f of thediffusion cell shall incorporate suitable fittings for the intro-duction and exhaust of gas without significant loss or leakage.7.1.2.4 It is desirable to thermostatically control the diffu-sion cell. A simple resistive heater, attached to the carrier gasside of the cell in such a manner as
26、to ensure good thermalcontact, is adequate for this purpose. A thermistor sensor andan 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 coils to remove some of the he
27、at.7.1.3 Catalyst Bed, a small metal tube with fittings forattachment to the inlet of the nitrogen gas pneumatic fittingcontaining 3 to5gof0.5%platinum or palladium catalyst onalumina5to provide an essentially oxygen-free carrier gas tothe diffusion cell and to each package test station.7.1.4 Flowme
28、ter, a flowmeter having an operating range of5 to 100 mL/min is required to monitor the flow rate ofnitrogen carrier gas through each test station.7.1.5 Flow Switching ValvesTwo or more valves for theswitching of the nitrogen and test gas flow streams.7.1.6 Oxygen-Sensitive Coulometric Sensor, opera
29、ting at anessentially constant efficiency is employed to monitor thequantity of oxygen transmitted.7.1.7 Load ResistorThe current generated by the coulo-metric cell shall pass through a resistive load across which theoutput voltage is measured.Typical values for load resistors are5.3 ohm and 53 ohm.
30、 These values yield a convenientrelationship between the output voltage and the oxygen trans-mission rate as expressed in terms of cm3(STP)/pkgd.4The sole source of supply of the suitable apparatus, such as that embodied inseveral OXTRAN models, known to the committee at this time is available fromM
31、ocon Inc., 7500 Boone Ave. North, Minneapolis, MN 55428. If you are aware ofalternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee1, which you may attend.5The sole s
32、ource of supply of a suitable catalyst known to the committee at thistime can be obtained from Englehard Industries Division, Chemical Dept., 429Delancey Street, Newark, NJ 07105. If you are aware of alternative suppliers, pleaseprovide this information to ASTM International Headquarters. Your comme
33、nts willreceive careful consideration at a meeting of the responsible technical committee1,which you may attend.FIG. 1 Arrangement of Components when Reference Film is Usedto Calibrate System for Package TestingF 1307 02 (2007)27.1.8 Voltage RecorderThe voltage across the load resis-tor is measured
34、and recorded using a strip-chart potentiometer,data-logger or other suitable device. The instrument or systemshould be able to measure a full-scale voltage of 50 mV. Itshould be able to measure voltages as low as 0.10 mV with aresolution of at least 10 V. An input impedance of 5000 ohmor higher is a
35、cceptable.8. 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 percent. The carrier gas shallbe dry and contain not more than 100 ppm of oxygen. Acommercially available mixture known a
36、s “forming gas” issuitable.8.2 Sealing GreaseA high-viscosity silicone stopcockgrease or a high-vacuum grease is required for sealing thecalibration film in the diffusion cell.8.3 Oxygen Test GasThe test gas shall be dry and containnot less than 99.5 % oxygen (except as provided for in 14.8).9. Tech
37、nical Precautions9.1 Extended use of the test unit with no moisture in the gasstream may result in a noticeable decrease in output andresponse time from the sensor (equivalent to an increase in thecalibration factor, Q). This condition is due to drying out of thesensor.9.2 Temperature is a critical
38、parameter affecting the mea-surement of O2GTR. Careful temperature control can help tominimize variations due to temperature fluctuations. Duringtesting, monitor and record the temperature, periodically, to thenearest 0.5C. Report the average temperature and the range oftemperatures found during a t
39、est.9.3 The sensor will require a relatively long time to stabilizeat a low reading characteristic of a good barrier after it has beenused to test a barrier such as low-density polyethylene. For thisreason, materials of comparable gas transmission qualitiesshould be tested together.9.4 Back diffusio
40、n of air into the unit is undesirable. Takecare, therefore, 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.9.5 The gas-permeability characteristics of some barriermaterials are altered by exposure to water vapor. I
41、f a packageis to be exposed and tested in normal laboratory air (20.8 %O2), the ambient relative humidity should be monitored to thenearest 3 %. This may be accomplished using a sling psy-chrometer or other method of comparable accuracy. Report theaverage and range of relative humidities measured du
42、ring thetest.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 1898.11. Test Specimens11.1 Test packages shall be representative of the populationand shall be free of
43、non-typical defects.12. Calibration12.1 General ApproachThe oxygen sensor used in thismethod is a coulometric device that yields a linear output aspredicted by Faradays Law. Since this sensor has an efficiencyof 95 to 98 % it is almost an absolute “yardstick” that does notrequire calibration. Experi
44、ence has shown, however, that undersome circumstances the sensor may become depleted ordamaged to the extent that efficiency and response are im-paired. For this reason, the method incorporates means forperiodic system calibration. This calibration is derived frommeasurements of a known-value “Refer
45、ence Package.”612.2 The reference package is essentially the lower-half of adiffusion cell (Fig. 1) in which a sheet of reference film ofknown O2GTR has been sealed and clamped. This creates a“package” into which oxygen will diffuse at a known rate.12.3 Assembling the Reference PackageEnsure the sen
46、soris bypassed to avoid swamping it with air, that is, no flow to thesensor. Unclamp the diffusion cell and open it. Apply a thinlayer of sealing grease (see 8.2) around the raised rim of thelower half of the diffusion cell. Insert the reference film in thediffusion cell and place it upon the grease
47、d surface, taking careto avoid wrinkles or creases. Lower the upper half of thediffusion cell into place and clamp both halves tightly together.12.4 Purging the SystemStart the nitrogen carrier gas flowand purge air from the upper and lower diffusion cell chambersusing a flow rate of 50 to 60 cm3/mi
48、n (as indicated by theflowmeter).After 3 or 4 min, reduce the flow rate to the desiredvalue between 5 and 15 cm3/min. Maintain this configurationfor 30 min.12.5 Establishing Zero Level of Reference FilmAfter thesystem has been flushed with nitrogen for 30 min, with thesensor bypassed, divert the nit
49、rogen carrier gas flow to thesensor. At this time the sensor output, as displayed on thevoltage recorder, will usually increase abruptly, indicating thatoxygen is entering the sensor with the carrier gas. The mostlikely sources of this oxygen are (1) outgassing of the sample,(2) leaks in the system, or (3) a combination of (1) and (2). Theoperator shall observe the recorder trace until the sensor outputcurrent stabilizes at a constant low value with no significanttrend in either direction. Note the observed deflection of thestrip chart recorder at this ti
