ASTM F1249-06(2011)
(Test Method)Standard Test Method for Water Vapor Transmission Rate Through Plastic Film and Sheeting Using a Modulated Infrared Sensor
Standard Test Method for Water Vapor Transmission Rate Through Plastic Film and Sheeting Using a Modulated Infrared Sensor
SIGNIFICANCE AND USE
The purpose of this test method is to obtain reliable values for the WVTR of plastic film and sheeting.
WVTR is an important property of packaging materials and can be directly related to shelf life and packaged product stability.
Data from this test method is suitable as a referee method of testing, provided that the purchaser and seller have agreed on sampling procedures, standardization procedures, test conditions, and acceptance criteria.
SCOPE
1.1 This test method covers a procedure for determining the rate of water vapor transmission through flexible barrier materials. The method is applicable to sheets and films up to 3 mm (0.1 in.) in thickness, consisting of single or multilayer synthetic or natural polymers and foils, including coated materials. It provides for the determination of (1) water vapor transmission rate (WVTR), (2) the permeance of the film to water vapor, and (3) for homogeneous materials, water vapor permeability coefficient.
Note 1—Values for water vapor permeance and water vapor permeability must be used with caution. The inverse relationship of WVTR to thickness and the direct relationship of WVTR to the partial pressure differential of water vapor may not always apply.
1.2 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.
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Standards Content (Sample)
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Designation: F1249 − 06(Reapproved 2011)
Standard Test Method for
Water Vapor Transmission Rate Through Plastic Film and
Sheeting Using a Modulated Infrared Sensor
This standard is issued under the fixed designation F1249; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope Determine the Precision of a Test Method
1.1 This test method covers a procedure for determining the
3. Terminology
rate of water vapor transmission through flexible barrier
3.1 Definitions:
materials. The method is applicable to sheets and films up to 3
3.1.1 water vapor permeability coeffıcient—the product of
mm (0.1 in.) in thickness, consisting of single or multilayer
the permeance and the thickness of the film. The permeability
synthetic or natural polymers and foils, including coated
is meaningful only for homogeneous materials, in which case
materials. It provides for the determination of (1) water vapor
it is a property characteristic of bulk material.
transmission rate (WVTR), (2) the permeance of the film to
3.1.1.1 Discussion—This quantity should not be used unless
water vapor, and (3) for homogeneous materials, water vapor
the relationship between thickness and permeance has been
permeability coefficient.
verified in tests using several thicknesses of the material. An
NOTE 1—Values for water vapor permeance and water vapor perme-
accepted unit of permeability is the metric perm centimeter, or
ability must be used with caution. The inverse relationship of WVTR to
1 g/m per day per mm Hg·cm of thickness. The SI unit is the
thickness and the direct relationship of WVTR to the partial pressure
mol/m ·s·Pa·mm. The test conditions (see 3.1) must be stated.
differential of water vapor may not always apply.
1.2 This standard does not purport to address all of the 3.1.2 water vapor permeance—the ratio of a barrier’s
safety concerns, if any, associated with its use. It is the WVTR to the vapor pressure difference between the two
responsibility of the user of this standard to establish appro- surfaces.
priate safety and health practices and determine the applica- 3.1.2.1 Discussion—An accepted unit of permeance is the
bility of regulatory limitations prior to use. metric perm, or 1 g/m per day per mm Hg. The SI unit is the
mol/m ·s·Pa. Since the permeance of a specimen is generally a
2. Referenced Documents
function of relative humidity and temperature, the test condi-
tions must be stated.
2.1 ASTM Standards:
D374 Test Methods for Thickness of Solid Electrical Insu-
3.1.3 water vapor transmission rate (WVTR)—the time rate
lation
of water vapor flow normal to the surfaces, under steady-state
D1898 Practice for Sampling of Plastics (Withdrawn 1998)
conditions, per unit area.
E96/E96M Test Methods for Water Vapor Transmission of
3.1.3.1 Discussion—An accepted unit of WVTR is g/m per
Materials
day. The test conditions of relative humidity and temperature
E104 Practice for Maintaining Constant Relative Humidity
where the humidity is the difference in relative humidity across
by Means of Aqueous Solutions
the specimens, must be stated.
E178 Practice for Dealing With Outlying Observations
E691 Practice for Conducting an Interlaboratory Study to 4. Summary of Test Method
4.1 A dry chamber is separated from a wet chamber of
known temperature and humidity by the barrier material to be
This test method is under the jurisdiction ofASTM Committee F02 on Flexible
tested. The dry chamber and the wet chamber make up a
Barrier Packaging and is the direct responsibility of Subcommittee F02.10 on
Permeation.
diffusion cell in which the test film is sealed. Water vapor
Current edition approved Aug. 1, 2011. Published November 2011. Originally
diffusing through the film mixes with the gas in the dry
approved in 1989. Last previous edition approved in 2006 as F1249 – 06. DOI:
chamberandiscarriedtoapressure-modulatedinfraredsensor.
10.1520/F1249-06R11.
This sensor measures the fraction of infrared energy absorbed
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
by the water vapor and produces an electrical signal, the
Standards volume information, refer to the standard’s Document Summary page on
amplitude of which is proportional to water vapor concentra-
the ASTM website.
tion.The amplitude of the electrical signal produced by the test
The last approved version of this historical standard is referenced on
www.astm.org. film is then compared to the signal produced by measurement
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1249 − 06 (2011)
FIG. 2 Conditioning System
FIG. 1 Measuring System
6.1.1.2 Diffusion Cell Sealing Surface—A flat rim around
the dry side of the diffusion cell. This is a critical sealing
of a calibration film of known water vapor transmission rate.
surface against which the test specimen is pressed; it shall be
This information is then used to calculate the rate at which
smooth and without radial scratches.
moisture is transmitted through the material being tested.
6.1.1.3 Diffusion Cell Air Passages—Two holes in the dry
half of the diffusion cell. This is necessary only in the earlier
5. Significance and Use
model WVTR instruments that have a separate conditioning
5.1 The purpose of this test method is to obtain reliable
rack and testing chamber. These shall incorporate O–rings
values for the WVTR of plastic film and sheeting.
suitable for sealing the diffusion cell to the test chamber
pneumatic fittings for the introduction and exhaust of air
5.2 WVTR is an important property of packaging materials
without significant loss or leakage.
and can be directly related to shelf life and packaged product
stability.
NOTE 2—Use of Multiple Diffusion Cells—Experience has shown that
arrangements using multiple diffusion cells are a practical way to increase
5.3 Data from this test method is suitable as a referee
the number of measurements that can be obtained in a given time. A
method of testing, provided that the purchaser and seller have
separate conditioning rack (Fig. 2) may be used that contains a manifold
agreed on sampling procedures, standardization procedures,
which connects the dry-chamber side of each individual diffusion cell to
test conditions, and acceptance criteria.
a dry-air source. Dry air is continually purging the dry chamber of those
cells that are connected to the conditioning rack while the humid chamber
6. Apparatus side is held at a specific relative humidity by distilled water or a
saturated-salt solution. It is desirable to thermostatically control the
6.1 This method utilizes water vapor transmission appara-
temperature of the conditioning rack as described in 6.1.3.
tus (Fig. 1) comprised of the following:
6.1.2 Test Chamber—A cavity into which the diffusion cell
6.1.1 Diffusion Cell—An assembly consisting of two metal
is inserted. Again, this is necessary only in the earlier model
halves which, when closed upon the test specimen, will
WVTR instruments that have a separate conditioning rack and
accurately define a circular area.Atypical acceptable diffusion
testing chamber. The test chamber shall incorporate means for
cell area is 50 cm . The volume enclosed by each cell half,
clamping the diffusion cell in accurate registration with pneu-
when clamped, is not critical; it should be small enough to
matic system openings to the dry-air source and the infrared
allow for rapid gas exchange, but not so small that an
detector. The chamber shall also provide a thermometer well
unsupported film that happens to sag or buckle will contact the
for the measurement of temperature.
top or bottom of the cell. A depth of approximately 6 mm
6.1.3 Diffusion Cell Temperature Control—It is desirable to
(0.250 in.) has been found to be satisfactory for 50-cm cells.
thermostatically control the temperature of the diffusion cell to
6.1.1.1 Diffusion Cell O–Ring —An appropriately sized
within 61°F.Asimpleresistiveheaterattachedtothestationin
groove machined into the humid chamber side of the diffusion
such a manner as to ensure good thermal contact is adequate
cellretainsaneopreneO–ring.Thetestareaisconsideredtobe
forthispurpose.Athermistorsensorandanappropriatecontrol
the area established by the inside contact diameter of the
circuit will serve to regulate the temperature unless measure-
compressed O–ring when the diffusion cell is clamped shut
ments are being made close to ambient temperature. In that
against the test specimen.
case it may be necessary to provide cooling coils to remove
some of the heat.
The sole source of supply of the apparatus known to the committee at this time
6.1.4 Flowmeter—Ameansforregulatingtheflowofdryair
is Mocon/Modern Controls, Inc., 7500 Boone Avenue North, Minneapolis, MN
within an operating range of 5 to 100 cc/min is required.
55428. If you are aware of alternative suppliers, please provide this information to
6.1.5 Flow-Switching Valves, for the switching of dry-gas
ASTM International Headquarters. Your comments will receive careful consider-
ation at a meeting of the responsible technical committee, which you may attend. flow streams of the water vapor transmission apparatus.
F1249 − 06 (2011)
6.1.6 Infrared Sensor—A water vapor detector capable of
sensing 1 µg/L of water, or, in other terms, 1 ppm by volume,
or 0.002 % relative humidity at 37.8°C.
6.1.7 Recording Device—A multirange strip chart recorder
or other appropriate instrument for measuring the voltage
developed by the signal amplifier.
6.1.8 Desiccant Drying System, shall be capable of reducing
the concentration of water vapor in the gas source down to less
than 0.5 ppm by volume or 0.001 % relative humidity at
37.8°C. In earlier model WVTR equipment, a separate desic-
cant drying system is needed for the conditioning rack and test
FIG. 3 Film Diffusion Cell
chamber.
6.1.9 Flow-Metering Valve—A fine-metering valve capable
of controlling the dry-gas flow rate to the test cell when the
10.2 Number of
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