1、Designation: F1307 14Standard Test Method forOxygen Transmission Rate Through Dry Packages Using aCoulometric Sensor1This standard is issued under the fixed designation F1307; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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 the determina-tion of the steady-state rate of transmission of oxygen gas
3、 intopackages. More specifically, the method is applicable topackages that in normal use will enclose a dry environment.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 is
4、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. Referenced Documents2.1 ASTM Standards:2D1434 Test Method for Determining Gas Permeability Char-acteristics of Plastic Film
5、and SheetingD1898 Practice for Sampling of Plastics (Withdrawn 1998)3D3985 Test Method for Oxygen Gas Transmission RateThrough Plastic Film and Sheeting Using a CoulometricSensorE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definiti
6、ons of Terms Specific to This Standard:3.1.1 oxygen gas transmission rate (O2GTR)as applied toa package, is the quantity of oxygen gas passing through thesurface of the package (PKG) per unit of time.3.1.1.1 DiscussionThe SI unit of transmission rate is themol/s. The test conditions, including tempe
7、rature, oxygenpartial pressure and humidity on both sides of the package,must be stated. A commonly used unit of O2GTR is thecm3(STP)/(PKGd), where 1 cm3at Standard Temperature andPressure (STP = 273.15K; 1.013 105Pa) is 44.62 106moland one day is 86 400 s.3.1.2 oxygen permeability coeffcient (PO2)t
8、he product ofthe permeance and thickness of the barrier.3.1.2.1 DiscussionThe permeability is meaningful 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 ve
9、rified in tests using several thicknesses of thematerial. The SI unit of permeability is the mol/(msPa). Thetest conditions must be stated.3.1.3 oxygen permeance (PO2)the ratio of the O2GTR tothe difference between the partial pressure of O2on the twosides of the package wall.3.1.3.1 DiscussionThe S
10、I unit of permeance is the mol/(sPa). The test conditions (see 4.2) must be stated.4. Summary of Test Method4.1 This test method employs a coulometric oxygen sensorand associated equipment in an arrangement similar to thatdescribed in Test Method D3985. Oxygen gas transmission rate(O2GTR) is determi
11、ned after the package has been mounted ona test fixture and has equilibrated in the test environment.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 oxy
12、gen. The package may be exposedin ambient room air which contains 20.8 % oxygen, or im-mersed in an atmosphere 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 magni
13、tude of which is proportional to theamount of oxygen flowing into the detector per unit of time.5. Significance 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 o
14、n1This 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 1990. Last previous edition approved in 2007 as F1307
15、 02 (2007).DOI: 10.1520/F1307-14.2For 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 o
16、f this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1experience, must be used to correlate package performancewith O2GTR. This test method is suitable as a referee methodof testing, p
17、rovided that the user and source have agreed onsampling procedures, standardization procedures, testconditions, 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. Interferi
18、ng 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 electrolyte.7. Apparatus7.1 Oxygen Gas Transmission Apparatus, as diagrammed inFig. 1 with the following:
19、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 mul-tiple package test stations are a practical way to increase thenumber of measurements that can
20、 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 carrier gas sidesof those packages that are not connected to the sensor. Eithertest gas (100 % oxyg
21、en) 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 calibration, willaccurately define a circular area of that film. Typical diffusioncell areas are 1
22、00 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 which happens to sag or bulgewill contact the top or bottom of the cell. Means shall beprovided for th
23、e 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 be the areaestablished by the inside contact diameter of the compressedO-ring when the diffusion c
24、ell 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 cell.7.1.2.2 The nitrogen (or carrier gas) side of the diffusion cellshall have a flat raised rim.
25、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 half of thediffusion cell shall incorporate suitable fittings for the intro-duction and exhaust of gas
26、 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 to ensure good thermalcontact, is adequate for this purpose. A thermistor sensor andan appropriate
27、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 heat.7.1.3 Catalyst Bed, a small metal tube with fittings forattachment to the inlet of the nitrogen
28、gas pneumatic fittingcontaining 3 to5gof0.5%platinum or palladium catalyst onalumina to provide an essentially oxygen-free carrier gas to thediffusion cell and to each package test station.7.1.4 Flowmeter, a flowmeter having an operating range of5 to 100 mL/min is required to monitor the flow rate o
29、fnitrogen 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, operating at anessentially constant efficiency is employed to monitor thequantity of oxygen transmitted.
30、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 aresuch that the values yield a convenient relationship between theoutput voltage and the oxygen transmission rate as exp
31、ressed interms of cm3(STP)/PKGd.7.1.8 Voltage RecorderThe voltage across the load resis-tor is measured 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 vo
32、ltages as low as 0.10 mV with aresolution of at least 10 V. An input impedance of 5000 ohmor higher is acceptable.8. Reagents and Materials8.1 Nitrogen Carrier Gas, consisting of a nitrogen andhydrogen mixture in which the percentage of hydrogen shallFIG. 1 Arrangement of Components when Reference F
33、ilm isUsed to Calibrate System for Package TestingF1307 142fall 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 as “forming gas” issuitable.8.2 Sealing GreaseA high-viscosity silicone stopcockgrease or
34、 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. Technical Precautions9.1 Extended use of the test unit with no moisture in the gasstream may
35、 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 parameter affecting the mea-surement of O2GTR. Careful temperature control can help tomi
36、nimize 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 test.9.3 The sensor will require a relatively long time to stabilizeat a low reading char
37、acteristic 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 diffusion of air into the unit is undesirable. Takecare, therefore, to ensure that there is a fl
38、ow 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. If a packageis to be exposed and tested in normal laboratory air (20.8 %O2), the ambient
39、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 during thetest.10. Sampling10.1 The sampling units used for the determination ofO2GTR shal
40、l be representative of the quantity of product forwhich the data are required, in accordance with PracticeD1898.11. Test Specimens11.1 Test packages shall be representative of the populationand shall be free of non-typical defects.12. Calibration12.1 General ApproachThe oxygen sensor used in thismet
41、hod 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. Experience has shown, however, that undersome circumstances the sensor may become depleted orda
42、maged 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 “Reference Package.”12.2 The reference package is essentially the lower-half of adiffusion cell
43、 (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 sensoris bypassed to avoid swamping it with air, that is, no flow to thesensor. Unclamp the d
44、iffusion 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 greased surface, taking careto avoid wrinkles or creases. Lower the upper half of thediffusion c
45、ell 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/min (as indicated by theflowmeter).After 3 or 4 min, reduce the flow rate to the desiredvalu
46、e 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 nitrogen carrier gas flow to thesensor. At this time the sensor output, as displayed on thevo
47、ltage 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 t
48、he sensor outputcurrent stabilizes at a constant low value with no significanttrend in either direction. Note the observed deflection of thestrip chart recorder at this time and label it E0.12.6 Once the zero level (E0) has been established, switch toa flow of oxygen on the test gas side of the diff
49、usion cell.Nitrogen will continue to flow on the downstream side of thecell.12.7 Establishing a Steady-State O2GTRThe sensoroutput, as displayed by the strip-chart recorder, should increaseand gradually level off, approaching a constant value (Ee).Record the observed final steady-state value of Ee.12.8 Temperature of the Reference FilmIt is desirable thatsystem calibration should be conducted at the temperature forwhich the reference films O2GTR is cited. Apply an appro-priate correction to the rate that the temperature differs fromthat value. Temp
