1、Designation: D3985 17Standard Test Method forOxygen Gas Transmission Rate Through Plastic Film andSheeting Using a Coulometric Sensor1This standard is issued under the fixed designation D3985; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、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 transmission of
3、 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 (OTR), (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 OTR. There may be other methods of OTRdetermination that use other oxygen sensors and procedures.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement a
5、re included in thisstandard.1.4 This standard does not purport to address all of thesafety problems, 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
6、prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization Technic
7、alBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1434 Test Method for Determining Gas Permeability Char-acteristics of Plastic Film and SheetingD1898 Practice for Sampling of Plastics (Withdrawn 1998)3E691 Practice for Conducting an Interlaboratory Study toDetermine th
8、e Precision of a Test MethodF1927 Test Method for Determination of Oxygen Gas Trans-mission Rate, Permeability and Permeance at ControlledRelative Humidity Through Barrier Materials Using aCoulometric Detector3. Terminology3.1 Definitions:3.1.1 oxygen permeability coeffcient (PO2)the product ofthe p
9、ermeance and the thickness of film. The permeability ismeaningful only for homogeneous materials, in which case it isa property characteristic of the bulk material. This quantityshould not be used, unless the relationship between thicknessand permeance has been verified on tests using several differ
10、entthicknesses of the material. The SI unit of oxygen permeabilityis the mol/(msPa). The test conditions (see 3.1.3) must bestated.3.1.2 oxygen permeance (PO2)the ratio of the OTR to thedifference between the partial pressure of O2on the two sidesof the film. The SI unit of permeance is the mol/(m2s
11、Pa). Thetest conditions (see 5.1) must be stated.3.1.3 oxygen transmission rate (OTR)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 testconditions, inclu
12、ding temperature and oxygen partial pressureon both sides of the film must be stated.3.1.3.1 A commonly used unit of OTR is the cm3(STP)/(m2d) at one atmosphere pressure difference where 1 cm3(STP) is 44.62 mol, 1 atm is 0.1013 MPa, and one day is86.4 103s.The OTR in SI units is obtained by multiply
13、ing thevalue in inch-pound units by 5.163 1010.4. Summary of Test Method4.1 The oxygen gas transmission rate is determined after thesample has equilibrated in a dry test environment. In this1This test method is under the jurisdiction ofASTM Committee F02 on PrimaryBarrier Packaging and is the direct
14、 responsibility of Subcommittee F02.10 onPermeation.Current edition approved Nov. 15, 2017. Published December 2017. Originallyapproved in 1981. Last previous edition approved in 2010 as D3985 05 (2010)1.DOI: 10.1520/D3985-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orco
15、ntact 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 of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive
16、, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issu
17、ed by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1context, a “dry” environment is considered to be one in whichthe relative humidity is less than 1 %.4.2 The specimen is mounted as a sealed semi-barrierbetween two chambers at ambient atmospheric pressure. Onechamber is
18、slowly purged by a stream of nitrogen and the otherchamber contains oxygen. As oxygen gas permeates throughthe film into the nitrogen carrier gas, it is transported to thecoulometric detector where it produces an electrical current,the magnitude of which is proportional to the amount ofoxygen flowin
19、g into the detector per unit time.5. Significance and Use5.1 The OTR is an important determinant of the packagingprotection afforded by barrier materials. It is not, however, thesole determinant, and additional tests, based on experience,must be used to correlate packaging performance with OTR. Itis
20、 suitable as a referee method of testing, provided that thepurchaser and the seller have agreed on sampling procedures,standardization procedures, test conditions, and acceptancecriteria.5.2 Limited statistical data on correlations with Test MethodD1434 methods are available4; however, the oxygen tr
21、ansmis-sion rate of a standard reference material (see 12.1)asdetermined manometrically by NIST, is in good agreementwith the values obtained in the coulometric interlaboratory testusing material from the same manufacturing lot. Thus, this testmethod may be used as a referee method.6. Interferences6
22、.1 The presence of certain interfering 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 sensorthro
23、ugh reaction with the potassium hydroxide electrolyte.7. Apparatus7.1 Oxygen Gas Transmission Apparatus, as diagrammed inFig. 1 with the following: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 enclo
24、sed 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 beprovided with a thermometer well for measuring t
25、emperature.7.1.1.1 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 that areaestablished by the inside contact diameter of the compressedO-ring when the diffusion cell is clamped shut ag
26、ainst 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.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report
27、 RR:D20-1085. ContactASTM CustomerService at serviceastm.org.FIG. 1 A Practical Arrangement of Components for the Measurement of Oxygen Transmission Rate Using the Coulometric MethodD3985 1727.1.1.2 The nitrogen (or carrier gas) side of the diffusion cellshall have a flat raised rim. Since this rim
28、is a critical sealingsurface against which the test specimen is pressed, it shall besmooth and flat, without radial scratches.7.1.1.3 Diffusion Cell Pneumatic FittingsThe diffusioncell shall incorporate suitable fittings for the introduction andexhaust of gases without significant loss or leakage.7.
29、1.1.4 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 measurements are being made close t
30、oambient temperature. In this case, it is desirable to providecooling capability to remove some of the heat.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. Valving
31、 connects the carrier gas side of each individualdiffusion cell to the sensor in a predetermined pattern. Carriergas is continually purging the carrier gas sides of those cellsthat are not connected to the sensor. Either test gas or carriergas, as is appropriate, purges the test gas chamber of anyin
32、dividual cell.7.1.2 Catalyst BedA small metal tube with fittings forattachment to the inlet on the nitrogen side of the diffusion cellshall contain 3 to5gof0.5%platinum or palladium catalystson alumina to provide an essentially oxygen-free carrier gas.7.1.3 FlowmeterA flowmeter having an operating r
33、angefrom 5 to 100 mL/min is required to monitor the flow rate ofthe nitrogen carrier gas.7.1.4 Flow Switching ValvesValves for the switching ofthe nitrogen and test gas flow streams.7.1.5 Coulometric SensorAn oxygen-sensitive coulomet-ric sensor (see Note 1) operating at an essentially constanteffic
34、iency shall be used to monitor the quantity of oxygentransmitted.NOTE 1It is deemed advisable upon initial setup of the voltagerecorder and periodically thereafter to check the response of the recorderon all ranges to a suitable voltage input.7.1.6 Load ResistorThe current generated by the coulo-met
35、ric cell shall pass through a resistive load across which theoutput voltage is measured. Typical values for the load resistorare such that the values yield a convenient relationship betweenthe output voltage and the oxygen transmission rate in standardunits cm3(STP)/(m2d).7.1.7 Voltage RecorderA mul
36、tirange, potentiometer stripchart recorder may be used for measuring the voltage devel-oped across the load resistor. The recorder should be capable ofmeasuring a full-scale voltage of 50 mV. It should be capableof measuring voltages as low as 0.100 mV and have aresolution of at least 10 V. An input
37、 impedance of 1 megohmor higher is acceptable.8. Reagents and Materials8.1 Nitrogen Carrier Gas shall consist 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.Acommerc
38、iallyavailable mixture known as “forming gas” is suitable.8.2 Oxygen Test Gas shall be dry and contain not less than99.5 % oxygen (except as provided in 14.11).8.3 Sealing GreaseA high-viscosity silicone stopcockgrease or a high-vacuum grease is required for sealing thespecimen film in the diffusion
39、 cell.9. Precautions9.1 Extended use of the test unit, with no moisture in the gasstream, may in some older systems result in a noticeabledecrease in output and response time from the sensor (equiva-lent to an increase in the calibration factor, Q). This conditionis due to drying out of the sensor.9
40、.2 Temperature is a critical parameter affecting the mea-surement of OTR. Careful temperature control can help tominimize variations due to temperature fluctuations. Duringtesting, the temperature shall be monitored to the nearest0.5C. The average temperature and the range of temperaturesfound durin
41、g a test shall both be reported.9.3 The sensor will require a relatively long time to stabilizeto a low reading characteristic of a good barrier after it hasbeen used to test a barrier such as low-density polyethylene.For this reason, materials of comparable gas transmissionqualities should be teste
42、d together.9.4 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 be lowwhen the instrument is not being used.9.5 Elevated temperatures can be used to hasten specimenoutgassing, pr
43、ovided 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 sampling units used for the determination of OTRshall be representative of the quantity of
44、product for which thedata are required, in accordance with Practice D1898. Careshall be taken to ensure that samples are representative ofconditions across the width and along the length of a roll offilm.11. Test Specimens11.1 Test specimens shall be representative of the materialbeing tested and sh
45、all 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.), using a calibrated dial gage (or equivalent)at a minimum of five points distributed over the en
46、tire 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 diffusionD3985 173cell shall be reported (for example
47、, “side II was mountedfacing the oxygen side of the diffusion cell”).12. Calibration12.1 General ApproachThe oxygen sensor used in thistest method is a coulometric device that yields a linear outputas predicted by Faradays Law. In principle, four electrons areproduced by the sensor for each molecule
48、 of oxygen that passesinto it. Considering that the sensor is known to have a basicefficiency of 95 to 98 %, it may be considered an “intrinsic”standard5that does not require calibration, and can thus beused as a reference method.12.2 Experience has shown, however, that under somecircumstances the s
49、ensor may become depleted or damaged tothe extent that efficiency and response are impaired. For thatreason, this test method incorporates means for a periodicsensor evaluation. This evaluation is derived from measure-ments of a known-value “reference package.” Experienceindicates however, that a specimen-to-specimen variability ofthe reference material is such that a change should never bemade in the calibration factor, as the result of a measurementusing a single sheet of the reference material.12.3 Establishing a System Calibration Constant
