ASTM F1927-98e1
(Test Method)Standard Test Method for Determination of Oxygen Gas Transmission Rate, Permeability and Permeance at Controlled Relative Humidity Through Barrier Materials Using a Coulometric Detector
Standard Test Method for Determination of Oxygen Gas Transmission Rate, Permeability and Permeance at Controlled Relative Humidity Through Barrier Materials Using a Coulometric Detector
SCOPE
1.1 This test method covers a procedure for determination of the rate of transmission of oxygen gas, at steady-state, at a given temperature and %RH level, through film, sheeting, laminates, co-extrusions, or plastic-coated papers or fabrics. This test method extends the common practice dealing with zero humidity or, at best, an assumed humidity. Humidity plays an important role in the oxygen gas transmission rate (O2GTR) of many materials. This test method provides for the determination of oxygen gas transmission rate (O2GTR), the permeance of the film to oxygen gas (P'O2), and oxygen permeability coefficient (P''O2) in the case of homogeneous materials at given temperature and %RH levels(s).
1.2 The values stated in SI units are to be regarded as the standard.
1.3 This standard does not purport to address all of the safety concerns, 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. Specific precautionary statements are given in Section 9.
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e1
Designation: F 1927 – 98
Standard Test Method for
Determination of Oxygen Gas Transmission Rate,
Permeability and Permeance at Controlled Relative Humidity
Through Barrier Materials Using a Coulometric Detector
This standard is issued under the fixed designation F 1927; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Reference to a research report was added to Section 17 in February 2000.
1. Scope by Means of Aqueous Solutions
E 691 Practice for Conducting an Interlaboratory Study to
1.1 This test method covers a procedure for determination
Determine the Precision of a Test Method
of the rate of transmission of oxygen gas, at steady-state, at a
given temperature and %RH level, through film, sheeting,
3. Terminology
laminates, co-extrusions, or plastic-coated papers or fabrics.
3.1 Definitions:
This test method extends the common practice dealing with
3.1.1 oxygen permeability coeffıcient (P9O )—the product
zero humidity or, at best, an assumed humidity. Humidity plays
of the permeance and the thickness of the film. The permeabil-
an important role in the oxygen gas transmission rate (O GTR)
ity is meaningful only for homogeneous materials, in which
of many materials. This test method provides for the determi-
case it is a property characteristic of the bulk material. This
nation of oxygen gas transmission rate (O GTR), the per-
quantity should not be used unless the relationship between
meance of the film to oxygen gas (P8O ), the permeation
thickness and permeance has been verified on tests using
coefficient of the film to its thickness (PO ), and oxygen
several different thicknesses of the material. The SI unit of
permeability coefficient (P9O ) in the case of homogeneous
oxygen permeability is the mol/m·s·Pa. The test conditions
materials at given temperature and %RH level(s).
(see 3.1.4) must be stated.
1.2 The values stated in SI units are to be regarded as the
3.1.2 oxygen permeance (P8O )—the ratio of O GTR to the
2 2
standard.
difference between the partial pressure of O on the two sides
1.3 This standard does not purport to address all of the
of the film. The SI unit of permeance is the mol/m · s · Pa. The
safety concerns, if any, associated with its use. It is the
test conditions (see 3.1.4) must be stated.
responsibility of the user of this standard to establish appro-
3.1.3 oxygen permeation coeffıcient (PO )—the ratio of
priate safety and health practices and determine the applica-
O GTR to the thickness of the film. The SI unit of permeance
bility of regulatory limitations prior to use. Specific precau-
is the mol/m · s · cm. The permeation coefficient is meaningful
tionary statements are given in Section 9.
only for homogeneous materials, in which case it is a property
2. Referenced Documents characteristic of the bulk material. This quantity should not be
used unless the relationship between thickness and transmis-
2.1 ASTM Standards:
sion rate is known.
D 1434 Test Method for Gas Transmission Rate of Plastic
3.1.4 oxygen transmission rate—at a given temperature and
Film and Sheeting
3 %RH (O GTR), the quantity of oxygen gas passing through a
D 1898 Practice for Sampling of Plastics 2
unit area of the parallel surfaces of a plastic film per unit time
D 3985 Test Method for Oxygen Gas Transmission Rate
under the conditions of test. The SI unit of transmission rate is
Through Plastic Film and Sheeting Using a Coulometric
the mol/m · s. The test conditions, including temperature,
Sensor
%RH and oxygen partial pressure on both sides of the film
E 104 Practice for Maintaining Constant Relative Humidity
must be stated.
3.1.5 transmission rate (O GTR)—a commonly used metric
3 2
unit of O GTR is the cm (STP)/m · d at one atmosphere
This test method is under the jurisdiction of ASTM Committee F-2 on Flexible
pressure differential where: 1 cm (STP) is 44.62 μmol, 1 atm is
Barrier Materials and is the direct responsibility of Subcommittee F02.30 on Test 3
0.1013 MPa, and one day is 86.4 3 10 s. O GTR in SI units
Methods.
Current edition approved Oct. 10, 1998. Published March 1999.
Annual Book of ASTM Standards, Vol 15.09.
3 4
Annual Book of ASTM Standards, Vol 08.02. Annual Book of ASTM Standards, Vol 11.04.
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F 1927
is obtained by multiplying the value in metric units by 6. Interferences
-10 3
5.165 3 10 or the value in inch-pound units [(cm /STP/100
6.1 The presence of certain interfering substances in the
2 -9
in. · d)] by 8.005 3 10 .
carrier gas stream may give rise to unwanted electrical outputs
and error factors. Interfering substances include free chlorine
4. Summary of Test Method
and some strong oxidizing agents. Exposure to carbon dioxide
4.1 The oxygen gas transmission rate is determined after the should also be minimized to avoid damage to the sensor
sample has equilibrated in a given temperature and humidity through reaction with the potassium hydroxide electrolyte.
environment.
4.2 The specimen is mounted as a sealed semi-barrier 7. Apparatus
between two chambers at ambient atmospheric pressure. One
7.1 Oxygen Gas Transmission Apparatus, as diagramed in
chamber is slowly purged by a stream of nitrogen at a given
Fig. 1 and described following. Alternative systems need to be
temperature and %RH and the other chamber is purged by a
evaluated to ensure equivalent performance.
stream of oxygen at the same temperature as the N stream but
7.1.1 Diffusion Cell, consisting of two metal halves, that,
may have a different %RH than the N stream. In this case the
2 when closed upon the test specimen, will accurately define a
environment would more closely simulate actual shelf condi-
circular area. Typical acceptable diffusion cell areas are 100
tions. As oxygen gas permeates through the film into the
and 50 cm . The volume enclosed by each cell half, when
nitrogen carrier gas, it is transported to the coulometric
clamped, is not critical: it should be small enough to allow for
detector where it produces an electrical current, the magnitude
rapid gas exchange, but not so small that an unsupported film
of which is proportional to the amount of oxygen flowing into
which happens to sag or bulge will contact the sides of the cell.
the detector per unit time.
The diffusion cell shall be provided with a temperature
measuring and controlling capability and a means to measure
5. Significance and Use
and control relative humidity.
5.1 O GTR at a given temperature and %RH is an important 7.1.1.1 Temperature control is critical because RH can vary
determinant of the packaging protection afforded by barrier as much as 5 % RH/°C in certain temperature regions. A
compact design of the diffusion cell structure with associated
materials. It is not, however the sole determinant, and addi-
tional tests, based on experience, must be used to correlate controls would lend itself to better temperature control. The
temperature should be controlled to 60.5°C or better.
packaging performance with O GTR. It is suitable as a referee
method of testing, provided that purchaser and seller have 7.1.1.2 O-Ring—An appropriately sized groove, machined
agreed on sampling procedures, standardization procedures, into the oxygen (or test gas) side of the diffusion cell, retains a
test conditions and acceptance criteria. neoprene O-ring. The test area is considered to be that area
FIG. 1 A Practical Arrangement of Components for the Measurement of Oxygen Transmission Rate Under Precise Relative Humidity
Conditions Using the Coulometric Method
F 1927
established by the inside contact diameter of the compressed 7.1.7.1 Placement of the RH detectors in the diffusion cells
O-ring when the diffusion cell is clamped shut against the test is important because relative humidity will change whenever
the temperature of the relative humidity source and diffusion
specimen. The area, A, can be obtained by measuring the inside
cells differ.
diameter of the imprint left by the O-ring on the specimen after
7.1.7.2 The RH detectors should periodically be calibrated
it has been removed from the diffusion cell.
against saturated salt solutions (see Practice E 104) or NIST
7.1.1.3 The nitrogen (or carrier gas) side of the diffusion cell
traceable devices.
shall have a flat raised rim. Since this rim is a critical sealing
surface against which the test specimen is pressed, it shall be
8. Reagents and Materials
smooth and flat, without radial scratches.
8.1 Nitrogen Carrier Gas, consisting of a nitrogen and
7.1.1.4 Diffusion Cell Pneumatic Fittings—Each half of the
hydrogen mixture in which the percentage of hydrogen shall
diffusion cell shall incorporate suitable fittings for the intro-
fall between 0.5 and 3.0 volume %. The carrier gas shall be dry
duction and exhaust of gasses without significant loss or
and contain not more than 100 ppm of oxygen. A commercially
leakage.
available mixture known as “forming gas” is suitable.
7.1.1.5 Experience has shown that arrangements using mul-
8.2 Oxygen Test Gas, shall be dry and contain not less than
tiple diffusion cells are a practical way to increase the number
99.5 % oxygen (except as provided in 14.10).
of measurements which can be obtained from a coulometric
8.3 Water to Generate %RH—Double or triple-distilled
sensor. A valving manifold shall connect the carrier gas side of
water is recommended (not deionized water) for precise
each individual diffusion cell to the sensor in a preselected
relative humidity generation and to avoid scale build up.
pattern. Carrier gas is continually purging the carrier gas sides
8.4 Sealing Grease—A high-viscosity hydrocarbon grease
of those cells that are not connected to the sensor. Either test
(preferred) or a high-vacuum grease is required for sealing the
gas or carrier gas, as is appropriate, purges the test gas chamber specimen film in the diffusion cell.
of any individual cell.
9. Precautions
7.1.2 Catalyst Bed—Should be used on the carrier gas (N )
9.1 Temperature is a critical parameter affecting the mea-
side of the diffusion cell assembly to provide an essentially
surement of O GTR. Careful temperature control will help to
oxygen free carrier gas. Palladium catalyst on alumina con- 2
minimize variations due to temperature fluctuations. During
verts O molecules into H O, thus virtually eliminating O
2 2 2
equilibration and testing the temperature shall be monitored
molecules in the carrier gas.
7 periodically. Should this temperature exceed 60.5°C after
7.1.3 Oxygen gas transmission apparatus shall have the
reaching the desired temperature, report the average tempera-
capability of measuring, at a variety of relative levels includ-
ture and the range of temperatures found during the test.
ing, zero RH to 90 % RH at a wide range of temperatures.
9.2 The sensor will require a relatively long time to stabilize
7.1.4 Package testing at given temperature and %RH levels
to a low reading characteristic of a good barrier after it has
to be optional if it is not included in the basic configuration.
been used to test a poorer barrier such as low density
7.1.5 Coulometric Sensor—An oxygen-sensitive coulomet-
polyethylene. For this reason, materials of comparable gas
ric sensor operating at an essentially constant efficiency shall
transmission qualities should be tested together.
be used to monitor the quantity of oxygen transmitted.
9.3 Back diffusion of air into the unit is undesirable. Care
7.1.6 With computer controlled systems, the results are should be taken to ensure that there is a flow of nitrogen
through the system at all times. This flow can be low when the
printed out giving final results, time-history of equilibration,
ambient conditions of test, material being tested and date. instrument is not being used.
9.4 Elevated temperatures to hasten specimen out gassing is
Should a failure occur, the time of this occurrence and its cause
not recommended. RH is a function of temperature and,
and correction taken should be documented for operator
therefore, equilibrating at some other temperature than the test
analysis as to the validity of continued testing.
temperature would expose the sample to an incorrect RH
7.1.7 RH Detectors—Water sensitive solid-state devices are
during the equilibration process. The entire test should be run
used to monitor the relative humidity of the gases directly in
at constant temperature and constant RH.
the upper and lower halves of the cell.
10. Sampling
10.1 The samples used for the determination of O GTR
The sole source of supply of the apparatus, a suitable catalyst, known to the
shall be representative of the quality of product for which the
committee at this time is Englehard Industries Division, Chemical Department, 429
Delancey Street, Newark, NJ 07105. If you are aware of alternative suppliers, please
provide this information to ASTM Headquarters. Your comments will receive
careful consideration at a meeting of the responsible technical committee that you Hasegawa, S. (NIST) “National Basis of Accuracy in Humidity Measure-
may attend. ments,” ISA Transactions, Vol 25, No. 3, 1986, pp. 15–24.
7 9
The sole source of supply of suitable apparatus such as that embodied in several The sole source of supply of the apparatus, a suitable hydrocarbon grease such
later OX-TRAN models known to the committee at this time is available from as Apiezon T, known to the committee at this time is, Biddle Instruments, 510
MOCON/Modern Controls, Inc. 7500 Boone Ave N, Minneapolis, MN 55428. If Township Road, Blue Bell, PA 19422. If you are aware of alternative suppliers,
you are aware of alternative suppliers, please provide this information to ASTM please provide this information to ASTM Headquarters. Your comments will receive
Headquarters. Your comments will receive careful consideration at a meeting of the careful consideration at a meeting of the responsible technical committee that you
responsible technical committee that you may attend. may attend.
F 1927
NOTE 1— Caution—The O GTR of the reference film may be ad-
data are required, in accordance with Practice D 1898. Care
versely affected by water vapor in the test gas or the carrier gas, therefore
shall be taken to ensure that film samples are representative of
detector evaluation tests should be run at
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