ASTM D3985-05(2010)e1
(Test Method)Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using a Coulometric Sensor
Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using a Coulometric Sensor
SIGNIFICANCE AND USE
The OTR is an important determinant of the packaging protection afforded by barrier materials. It is not, however, the sole determinant, and additional tests, based on experience, must be used to correlate packaging performance with OTR. It is suitable as a referee method of testing, provided that the purchaser and the seller have agreed on sampling procedures, standardization procedures, test conditions, and acceptance criteria.
Limited statistical data on correlations with Test Method D1434 methods are available ; however, the oxygen transmission rate of a standard reference material (see 12.1) as determined manometrically by NIST, is in good agreement with the values obtained in the coulometric interlaboratory test using material from the same manufacturing lot. Thus, this test method may be used as a referee method.
SCOPE
1.1 This test method covers a procedure for determination of the steady-state rate of transmission of oxygen gas through plastics in the form of film, sheeting, laminates, coextrusions, or plastic-coated papers or fabrics. It provides for the determination of (1) oxygen gas transmission rate (OTR), (2) the permeance of the film to oxygen gas (PO2), and (3) oxygen permeability coefficient (P'O2) in the case of homogeneous materials.
1.2 This test method does not purport to be the only method for measurement of OTR. There may be other methods of OTR determination that use other oxygen sensors and procedures.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D3985 − 05 (Reapproved 2010)
Standard Test Method for
Oxygen Gas Transmission Rate Through Plastic Film and
Sheeting Using a Coulometric Sensor
This standard is issued under the fixed designation D3985; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Editorial changes were made throughout in November 2010.
1. Scope F1927TestMethodforDeterminationofOxygenGasTrans-
mission Rate, Permeability and Permeance at Controlled
1.1 This test method covers a procedure for determination
Relative Humidity Through Barrier Materials Using a
of the steady-state rate of transmission of oxygen gas through
Coulometric Detector
plastics in the form of film, sheeting, laminates, coextrusions,
or plastic-coated papers or fabrics. It provides for the determi-
3. Terminology
nation of (1) oxygen gas transmission rate (OTR), (2) the
3.1 Definitions:
permeance of the film to oxygen gas (PO ), and (3) oxygen
3.1.1 oxygen permeability coeffıcient (P'O )—the product of
permeability coefficient (P'O ) in the case of homogeneous
the permeance and the thickness of film. The permeability is
materials.
meaningfulonlyforhomogeneousmaterials,inwhichcaseitis
1.2 Thistestmethoddoesnotpurporttobetheonlymethod
a property characteristic of the bulk material. This quantity
formeasurementofOTR.TheremaybeothermethodsofOTR
should not be used, unless the relationship between thickness
determination that use other oxygen sensors and procedures.
andpermeancehasbeenverifiedontestsusingseveraldifferent
thicknessesofthematerial.TheSIunitofoxygenpermeability
1.3 The values stated in SI units are to be regarded as
is the mol/(m·s·Pa). The test conditions (see 3.1.3) must be
standard. No other units of measurement are included in this
stated.
standard.
3.1.2 oxygen permeance (PO )—the ratio of the OTR to the
1.4 This standard does not purport to address all of the
difference between the partial pressure of O on the two sides
safety problems, if any, associated with its use. It is the
of the film.The SI unit of permeance is the mol/(m ·s·Pa).The
responsibility of the user of this standard to establish appro-
test conditions (see 5.1) must be stated.
priate safety and health practices and determine the applica-
3.1.3 oxygen transmission rate (OTR)—the quantity of
bility of regulatory limitations prior to use.
oxygen gas passing through a unit area of the parallel surfaces
of a plastic film per unit time under the conditions of test. The
2. Referenced Documents
SI unit of transmission rate is the mol/(m ·s). The test
2.1 ASTM Standards:
conditions, including temperature and oxygen partial pressure
D1434TestMethodforDeterminingGasPermeabilityChar-
on both sides of the film must be stated.
acteristics of Plastic Film and Sheeting 3
3.1.3.1 A commonly used unit of OTR is the cm (STP)/
D1898Practice for Sampling of Plastics (Withdrawn 1998) 2 3
(m ·d) at one atmosphere pressure difference where 1 cm
E691Practice for Conducting an Interlaboratory Study to
(STP) is 44.62 µmol, 1 atm is 0.1013 MPa, and one day is
Determine the Precision of a Test Method 3
86.4×10 s.TheOTRinSIunitsisobtainedbymultiplyingthe
−10
value in inch-pound units by 5.160×10 .
4. Summary of Test Method
ThistestmethodisunderthejurisdictionofASTMCommitteeF02onFlexible
Barrier Packaging and is the direct responsibility of Subcommittee F02.10 on
4.1 Theoxygengastransmissionrateisdeterminedafterthe
Permeation.
sample has equilibrated in a dry test environment. In this
Current edition approved Oct. 1, 2010. Published November 2010. Originally
ε1
approved in 1981. Last previous edition approved in 2005 as D3985–05 . DOI:
context, a “dry” environment is considered to be one in which
10.1520/D3985-05R10E01.
the relative humidity is less than 1%.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.2 The specimen is mounted as a sealed semi-barrier
Standards volume information, refer to the standard’s Document Summary page on
between two chambers at ambient atmospheric pressure. One
the ASTM website.
chamberisslowlypurgedbyastreamofnitrogenandtheother
The last approved version of this historical standard is referenced on
www.astm.org. chamber contains oxygen. As oxygen gas permeates through
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D3985 − 05 (2010)
FIG. 1 A Practical Arrangement of Components for the Measurement of Oxygen Transmission Rate Using the Coulometric Method
the film into the nitrogen carrier gas, it is transported to the and some strong oxidizing agents. Exposure to carbon dioxide
coulometric detector where it produces an electrical current, should also be minimized to avoid damage to the sensor
the magnitude of which is proportional to the amount of through reaction with the potassium hydroxide electrolyte.
oxygen flowing into the detector per unit time.
7. Apparatus
5. Significance and Use
7.1 Oxygen Gas Transmission Apparatus,asdiagrammedin
5.1 The OTR is an important determinant of the packaging
Fig. 1 with the following:
protection afforded by barrier materials. It is not, however, the
7.1.1 Diffusion Cell shall consist of two metal halves,
sole determinant, and additional tests, based on experience,
which, when closed upon the test specimen, will accurately
must be used to correlate packaging performance with OTR. It
define a circular area. The volume enclosed by each cell half,
is suitable as a referee method of testing, provided that the
when clamped, is not critical; it should be small enough to
purchaser and the seller have agreed on sampling procedures,
allow for rapid gas exchange, but not so small that an
standardization procedures, test conditions, and acceptance
unsupported film which happens to sag or bulge will contact
criteria.
the top or bottom of the cell. The diffusion cell shall be
5.2 LimitedstatisticaldataoncorrelationswithTestMethod provided with a thermometer well for measuring temperature.
D1434 methods are available ; however, the oxygen transmis-
7.1.1.1 O-Ring—An appropriately sized groove, machined
sion rate of a standard reference material (see 12.1)as
into the oxygen (or test gas) side of the diffusion cell, retains a
determined manometrically by NIST, is in good agreement
neoprene O-ring. The test area is considered to be that area
with the values obtained in the coulometric interlaboratory test
established by the inside contact diameter of the compressed
using material from the same manufacturing lot.Thus, this test
O-ring when the diffusion cell is clamped shut against the test
method may be used as a referee method.
specimen.Thearea, A,canbeobtainedbymeasuringtheinside
diameteroftheimprintleftbytheO-ringonthespecimenafter
6. Interferences
it has been removed from the diffusion cell.
6.1 The presence of certain interfering substances in the
7.1.1.2 Thenitrogen(orcarriergas)sideofthediffusioncell
carrier gas stream may give rise to unwanted electrical outputs
shall have a flat raised rim. Since this rim is a critical sealing
and error factors. Interfering substances include free chlorine
surface against which the test specimen is pressed, it shall be
smooth and flat, without radial scratches.
7.1.1.3 Diffusion Cell Pneumatic Fittings—The diffusion
Supporting data have been filed atASTM International Headquarters and may
cell shall incorporate suitable fittings for the introduction and
beobtainedbyrequestingResearchReportRR:D20-1085.ContactASTMCustomer
Service at service@astm.org. exhaust of gases without significant loss or leakage.
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D3985 − 05 (2010)
7.1.1.4 It is desirable to thermostatically control the diffu- 8.2 Oxygen Test Gas shall be dry and contain not less than
sioncell.Asimpleheatingorheating/coolingsystemregulated 99.5% oxygen (except as provided in 14.11).
to 60.5°C, is adequate for this purpose. A thermistor sensor
8.3 Sealing Grease—A high-viscosity silicone stopcock
andanappropriatecontrolcircuitwillservetoregulatethecell
grease or a high-vacuum grease is required for sealing the
temperature unless measurements are being made close to
specimen film in the diffusion cell.
ambient temperature. In this case, it is desirable to provide
cooling capability to remove some of the heat.
9. Precautions
7.1.1.5 Experience has shown that arrangements using mul-
9.1 Extendeduseofthetestunit,withnomoistureinthegas
tiple diffusion cells are a practical way to increase the number
stream, may in some older systems result in a noticeable
of measurements which can be obtained from a coulometric
decrease in output and response time from the sensor (equiva-
sensor.Valving connects the carrier gas side of each individual
lent to an increase in the calibration factor, Q). This condition
diffusion cell to the sensor in a predetermined pattern. Carrier
is due to drying out of the sensor.
gas is continually purging the carrier gas sides of those cells
that are not connected to the sensor. Either test gas or carrier
9.2 Temperature is a critical parameter affecting the mea-
gas, as is appropriate, purges the test gas chamber of any
surement of OTR. Careful temperature control can help to
individual cell.
minimize variations due to temperature fluctuations. During
7.1.2 Catalyst Bed—A small metal tube with fittings for
testing, the temperature shall be monitored to the nearest
attachmenttotheinletonthenitrogensideofthediffusioncell
0.5°C. The average temperature and the range of temperatures
shall contain 3 to5gof0.5% platinum or palladium catalysts
found during a test shall both be reported.
on alumina to provide an essentially oxygen-free carrier gas.
9.3 Thesensorwillrequirearelativelylongtimetostabilize
7.1.3 Flowmeter—A flowmeter having an operating range
to a low reading characteristic of a good barrier after it has
from 5 to 100 mL/min is required to monitor the flow rate of
been used to test a barrier such as low-density polyethylene.
the nitrogen carrier gas.
For this reason, materials of comparable gas transmission
7.1.4 Flow Switching Valves—Valves for the switching of
qualities should be tested together.
the nitrogen and test gas flow streams.
9.4 Back diffusion of air into the unit is undesirable. Care
7.1.5 Coulometric Sensor—An oxygen-sensitive coulomet-
should therefore be taken to ensure that there is a flow of
ric sensor (see Note 1) operating at an essentially constant
nitrogen through the system at all times. This flow can be low
efficiency shall be used to monitor the quantity of oxygen
when the instrument is not being used.
transmitted.
9.5 Elevated temperatures can be used to hasten specimen
NOTE 1—It is deemed advisable upon initial setup of the voltage
recorder and periodically thereafter to check the response of the recorder outgassing, provided that the treatment does not alter the basic
on all ranges to a suitable voltage input.
structure of the specimen (crystallinity, density, and so forth).
This can be accomplished by the use of the heaters in the
7.1.6 Load Resistor—The current generated by the coulo-
diffusion cells.
metric cell shall pass through a resistive load across which the
output voltage is measured.Typical values for the load resistor
10. Sampling
aresuchthatthevaluesyieldaconvenientrelationshipbetween
theoutputvoltageandtheoxygentransmissionrateinstandard
10.1 The sampling units used for the determination of OTR
3 2
units cm (STP)/(m ·d).
shall be representative of the quantity of product for which the
7.1.7 Voltage Recorder—A multirange, potentiometer strip
data are required, in accordance with Practice D1898. Care
chart recorder may be used for measuring the voltage devel-
shall be taken to ensure that samples are representative of
opedacrosstheloadresistor.Therecordershouldbecapableof
conditions across the width and along the length of a roll of
measuring a full-scale voltage of 50 mV. It should be capable
film.
of measuring voltages as low as 0.100 mV and have a
resolution of at least 10 µV.An input impedance of 1 megohm
11. Test Specimens
or higher is acceptable.
11.1 Test specimens shall be representative of the material
being tested and shall be free of defects, including wrinkles,
8. Reagents and Materials
creases, and pinholes, unless these are a characteristic of the
8.1 Nitrogen Carrier Gas shall consist of a nitrogen and
material being tested.
hydrogen mixture in which the percentage of hydrogen shall
11.2 Average thickness shall be determined to the nearest
fallbetween0.5and3.0volume%.Thecarriergasshallbedry
2.5µm(0.0001in.),usingacalibrateddialgage(orequivalent)
andcontainnotmorethan100ppmofoxygen.Acommercially
ataminimumoffivepointsdistributedovertheentiretestarea.
available mixture known as “forming gas” is suitable.
Maximum, minimum, and average values shall be recorded.
11.3 Ifthetestspecimenisofanasymmetricalconstruction,
The sole source of supply of the catalyst known to the committee at this time
the two surfaces shall be marked by appropriate distinguishing
isEnglehardIndustriesDivision,ChemicalDept.,429DelanceyStreet,Newark,NJ
marks and the orientation of the test specimen in the diffusion
07105. If you are aware of alternative suppliers, please provide this information to
cell shall be reported (for example, “side II was mounted
ASTM International Headquarters. Your comments will receive careful consider-
ation at a meeting of the responsible technical committee, which you may attend. facing the oxygen side of the diffusion cell”).
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D3985 − 05 (2010)
12. Calibration materials to a condition where their measured OTRs will be
reproducible. Previous experience should serve as the primary
12.1 General Approach—The oxygen sensor used in this
guide to the suitability of a given conditioning regimen. If a
test method is a coulometric device that yields a linear output
material is being tested with which the user has no previous
as predicted by Faraday’s Law. In principle, four electrons are
experience, the effect of conditioning time should be investi-
producedbythesensorforeachmoleculeofoxygenthatpasses
gated and a regimen selected such that there is no significant
into it. Considering that the sensor is known to have a basic
effect due to conditioning time. In any case, the conditioning
efficiency of 95 to 98 %, it may be considered an “intrinsic”
procedure used should be included in the report section.
standard that does not r
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