1、Designation: D3985 05 (Reapproved 2010)1Standard 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
2、or, in 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.1NOTEEditorial changes were made throughout in November 2010.1. Scope1.1 This test method
3、 covers a procedure for determinationof the steady-state rate of transmission 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 (OTR), (2) thepermeance of th
4、e film to oxygen gas (PO2), and (3) oxygenpermeability coefficient (PO2) in the 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 s
5、tated in SI units are to be regarded asstandard. No other units of measurement are 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
6、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 PermeabilityCharacteristics of Plastic Film and SheetingD1898 Practice for Sampling of Plastics3E691 Practice for Conducting a
7、n Interlaboratory Study toDetermine the Precision of a Test MethodF1927 Test Method for Determination of Oxygen GasTransmission Rate, Permeability and Permeance at Con-trolled Relative Humidity Through Barrier Materials Usinga Coulometric Detector3. Terminology3.1 Definitions:3.1.1 oxygen permeabili
8、ty coeffcient (PO2)the productof the permeance 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
9、verified on tests using several differentthicknesses 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. Th
10、e SI unit of permeance is the mol/(m2sPa). 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 th
11、e mol/(m2s). The test condi-tions, including temperature and oxygen partial pressure onboth 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 1cm3(STP) is 44.62 mol, 1 atm is 0.1013 MPa, and one day is86.4 3 103s. T
12、he OTR in SI units is obtained by multiplyingthe value in inch-pound units by 5.160 3 1010.4. Summary of Test Method4.1 The oxygen gas transmission rate is determined after thesample has equilibrated in a dry test environment. In thiscontext, a “dry” environment is considered to be one in whichthe r
13、elative humidity is less than 1 %.4.2 The specimen is mounted as a sealed semi-barrierbetween two chambers at ambient atmospheric pressure. Onechamber is slowly purged by a stream of nitrogen and the otherchamber contains oxygen. As oxygen gas permeates throughthe film into the nitrogen carrier gas,
14、 it is transported to the1This 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, 2010. Published November 2010. Originallyapproved in 1981. Last previous editio
15、n approved in 2005 as D3985 051. DOI:10.1520/D3985-05R10E01.2For 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.3
16、Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.coulometric detector where it produces an electrical current,the magnitude of which is proportional to the amount ofoxygen flowing into the detector per unit time.5. Significa
17、nce 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 suitable as a referee method of testing, prov
18、ided 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 transmis-sion rate of a standard reference mater
19、ial (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. Interferences6.1 The presence of certain interfering substan
20、ces 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 elec
21、trolyte.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 enclosed by each cell half,when clamped, is not cri
22、tical; 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 temperature.7.1.1.1 O-RingAn appropriately size
23、d 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 against the testspecimen. The area, A, can be ob
24、tained by measuring the insidediameter of the imprint left by the O-ring on the specimen afterit has been removed from the diffusion cell.7.1.1.2 The nitrogen (or carrier gas) side of the diffusion cellshall have a flat raised rim. Since this rim is a critical sealingsurface against which the test s
25、pecimen 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.7.1.1.4 It is desirable to thermostatically control the
26、 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 to4Supporting data have been filed at ASTM Internation
27、al Headquarters and maybe obtained by requesting Research Report RR:D20-1085.FIG. 1 A Practical Arrangement of Components for the Measurement of Oxygen Transmission Rate Using the Coulometric MethodD3985 05 (2010)12ambient temperature. In this case, it is desirable to providecooling capability to re
28、move 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 connects the carrier gas side of each individualdiffusion cell to the sensor in a pre
29、determined 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 anyindividual cell.7.1.2 Catalyst BedA small metal tube with fittings forattachment to the
30、inlet on the nitrogen side of the diffusion cellshall contain 3 to5gof0.5%platinum or palladium catalystson alumina5to provide an essentially oxygen-free carrier gas.7.1.3 FlowmeterA flowmeter having an operating rangefrom 5 to 100 mL/min is required to monitor the flow rate ofthe nitrogen carrier g
31、as.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 constantefficiency shall be used to monitor the quantity of oxygentransmitted.NOTE 1It is deemed ad
32、visable 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-metric cell shall pass through a resistive load across which theoutput voltage is measure
33、d. 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 multirange, potentiometer stripchart recorder may be used for measuring the voltage devel
34、-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 impedance of 1 megohmor higher is acceptable.8. Reagents and Materials8.1 Nitrogen Ca
35、rrier 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.Acommerciallyavailable mixture known as “forming gas” is suitable.8.2 Oxygen Test Gas shall be
36、 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 cell.9. Precautions9.1 Extended use of the test unit, with no moisture in the gasstre
37、am, 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.9.2 Temperature is a critical parameter affecting the mea-surement of OTR. Careful temp
38、erature 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 during a test shall both be reported.9.3 The sensor will require a relatively long time to
39、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 tested together.9.4 Back diffusion of air into the unit is undesirable. Careshould therefor
40、e 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, provided that the treatment does not alter the basicstructure of the specimen (crystalli
41、nity, 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 product for which thedata are required, in accordance with Practice D1898. Careshall b
42、e 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 shall be free of defects, including wrinkles,creases, and pinholes, unless these are a c
43、haracteristic 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 entire test area.Maximum, minimum, and average values shall be recorded.11.3 If the test
44、 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 mountedfacing the oxygen side of the diffusion cell”).12. Calibration12.1 Genera
45、l 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 of oxygen that passesinto it. Considering that the sensor is known to have a basicefficiency o
46、f 95 to 98 %, it may be considered an “intrinsic”5The sole source of supply of the catalyst known to the committee at this timeis Englehard Industries Division, Chemical Dept., 429 Delancey Street, Newark, NJ07105. If you are aware of alternative suppliers, please provide this information toASTM Int
47、ernational Headquarters. Your comments will receive careful consider-ation at a meeting of the responsible technical committee,1which you may attend.D3985 05 (2010)13standard6that does not require calibration, and can thus beused as a reference method.12.2 Experience has shown, however, that under s
48、omecircumstances the sensor 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”. Experienceindica
49、tes however, that a specimen-to-specimen variability ofthe reference material7is 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 (Used onlyon systems using a chart recorder to determine OTR)Determine the exposed area, A, of the calibrating reference film(see 7.1.1.1). Using the permeance value furnished with thereference film, determine the OTR through that film of thatarea (A). Use this value to determ
