ASTM F372-99

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
Designation: F 372 – 99
Standard Test Method for
Water Vapor Transmission Rate of Flexible Barrier Materials
Using an Infrared Detection Technique
This standard is issued under the fixed designation F 372; 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 3.1.2 water vapor permeance (of a body between two
specifiedparallelsurfaces)—theratioofitsWVTRtothevapor
1.1 This test method covers a rapid procedure for determin-
pressure difference between the two surfaces.An accepted unit
ing the rate of water vapor transmission of flexible barrier
of permeance is a metric perm, or 1 g/day·m ·mm Hg. Since
materials in film or sheet form. This test method is applicable
the permeance of a specimen is generally a function of relative
to sheets and films up to 3 mm in thickness, consisting of
humidity and temperature, the test conditions must be stated.
single-layer or multilayer synthetic or natural polymers and
metal foils including coated materials.
4. Summary of Test Method
1.2 This standard does not purport to address all of the
4.1 A dry chamber is separated from a wet chamber of
safety problems, if any, associated with its use. It is the
known temperature and humidity by the barrier material to be
responsibility of the user of this standard to establish appro-
tested. The time for a given increase in water vapor concen-
priate safety and health practices and determine the applica-
tration of the dry chamber is measured by monitoring the
bility of regulatory limitations prior to use.
differential between two bands in the infrared spectral region,
2. Referenced Documents one in which water molecules absorb and the other where they
do not. This information is then used to calculate the water
2.1 ASTM Standards:
vapor movement through a known area of barrier material.
D 374 Test Methods for Thickness of Solid Electrical Insu-
lation
5. Significance and Use
D 1898 Practice for Sampling of Plastics
5.1 The purpose of this test method is to rapidly obtain
E96 Test Methods for Water Vapor Transmission of Mate-
4 reliable values for the WVTR of barrier materials.
rials
5.2 The WVTR is an important property of packaging
E 104 Practice for Maintaining Constant Relative Humidity
5 materials, which can be related to shelf life and product
by Means of Aqueous Solutions
stability.
E 691 Practice for Conducting an Interlaboratory Study to
6 5.3 In any application, the WVTR of a barrier material is
Determine the Precision of a Test Method
determined by its permeance under the given conditions. In
3. Terminology most cases, the WVTR will increase when the absolute
humidity is increased on the wet side of the barrier and when
3.1 Definitions:
the temperature of the environment increases, particularly if a
3.1.1 water vapor transmission rate (WVTR) (of a body
polymeric material is the primary water vapor barrier in the
between two specified parallel surfaces)— the time rate of
construction.
water vapor flow normal to the surfaces, under steady condi-
5.4 Values for water vapor permeance and water vapor
tions, through unit area, under the conditions of test (for
permeability must be used with caution. The inverse relation-
example, temperature and relative humidity).An accepted unit
ship of WVTR to thickness and the direct relationship of
of WVTR is g/day·m . The test conditions must be stated.
WVTRtothepartialpressuredifferentialofthewatervaporare
not always linear.
This test method is under the jurisdiction ofASTM Committee F-2 on Flexible
6. Apparatus
Barrier Materials and is the direct responsibility of Subcommittee F02.30 on Test
6.1 Water Vapor TransmissionApparatus, (Fig. 1) with the
Methods.
Current edition approved May 10, 1999. Published July 1999. Originally following:
published as F 372 – 73. Last previous edition F 372 – 94.
6.1.1 Temperature Control, capable of maintaining humid
Annual Book of ASTM Standards, Vol 10.01.
chambers and test material at 37.8 6 0.1°C (100 6 0.2°F).
Annual Book of ASTM Standards, Vol 08.01.
Annual Book of ASTM Standards, Vol 04.06.
Annual Book of ASTM Standards, Vol 11.03.
6 7
Annual Book of ASTM Standards, Vol 14.02. Modern Controls, Inc. no longer supplies the IRD-2, but some are still in use.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
F372–99
FIG. 1 Functional Diagram of Diffusometer
6.1.2 Infrared Detection System, capable of detecting 8.2 The material shall be sampled in accordance with
changesof1µgofwatervaporperlitreorinotherterms1ppm standard methods of sampling applicable to the material under
by volume or 0.002 % relative humidity at 37.8°C. test. The sample shall be selected as representative of the
6.2 Micrometer, graduated to 0.0025 mm (0.10 mil) or material to be tested, and shall be of uniform thickness. If the
better, and accurate to 0.00125 mm (0.05 mil) to measure material is of nonsymmetrical construction, the two faces shall
specimen thickness. be designated by distinguishing marks (for example, on a
6.3 Analytical Balance , accurate to 0.0001 g. one-side-coated sample, “I” for the coated side and “II” for the
6.4 Clock or Watch. uncoated side).
6.5 Schwartz U-Shaped Drying Tube.
9. Test Specimens
6.6 Calcium Chloride Drying Tube.
9.1 Test specimens shall be representative of the sample.
6.7 Sponges.
Test at least three specimens by the same method. If the
surfaces of the sample differ, ensure that they are positioned
7. Reagent and Materials
8 properly relative to the wet and test chambers. Take care not to
7.1 Desiccant for Drying Air Stream.
9 contaminate the test area of the specimen.
7.2 Desiccant for Drying Tubes.
9.2 Determine the average thickness from measurements
7.3 Distilled Water, for controlling humidity at 100 %
taken to the nearest 0.0025 mm (0.10 mil) on the surface area
relative humidity at 37.8°C.
interfacing the humid chamber(s) and the test chamber. The
7.4 Zinc Sulfate Solution, saturated at 37.8°C.
number of measurements will depend upon the size of the total
7.5 Ammonium Sulfate Solution, saturated at 37.8°C.
interfacing area.
7.6 Sealing Grease.
10. Procedure for Gravimetric Calibration of Instrument
8. Sampling
and Preparation of Standard Film
8.1 Practice D 1898D 1898 provides guidance in develop-
10.1 Set the operating temperature in the humid chambers
ing sampling procedures.
within 1°F (0.5°C) of the desired temperature. Check the
sponges and dampen if necessary with distilled water for
100 % relative humidity, saturated zinc sulfate for 90 %
Linde Molecular Sieve, Type 4A, ⁄8-in. (3.2-mm) pellets from Union Carbide
relative humidity, or saturated ammonium sulfate for 81 %
Corp., Linde Div., Molecular Sieve Products, 120 Riverside Plaza, Chicago, IL
relative humidity.
60605, have been found suitable.
10.2 Purge the test chamber with dry air and then measure
Anhydrone,availablefromJ.T.BakerChemicalCo.,Phillipsburg,NJ,hasbeen
found satisfactory. the time for a given increase in water vapor concentration as
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
F372–99
the water transmits from the humid chamber(s) through the
g = weight of water vapor transmitted in time t.
film into the test chamber.
10.3 Repeat 10.2 until time measured remains constant.
11. Procedure for Measuring WVTR of Samples
10.4 Attach a charged and weighed Schwartz drying tube to
11.1 Control the temperatures and humidity in the humid
the air exit tube of the test chamber. Follow it with a charged
chambers in accordance with 10.1.
calcium chloride tube to prevent absorption of water vapor
11.2 Place the sample in the instrument and purge a few
from the laboratory atmosphere.
minutes with dry air.
10.5 Record the time of day (t ) and allow the unit to either
11.3 Discontinue purging and follow the increase in the
cycle or continually purge until sufficient water is absorbed in
water vapor concentration of the test chamber with time.
the Schwartz tube to obtain a reliable weight, 100 mg or more.
Record, purge, and repeat until time measured remains con-
10.6 Record the time of day upon completion ( t ), imme-
2 stant, that is, when the change being recorded for repetitive
diately close the stopcocks, remove the drying tubes and weigh
cycles differs by no more than 65 %. Calculate WVTR.
the Schwartz tube. The increase in weight ( W) is due to the
11.3.1 If the readout calibration procedure in accordance
water vapor absorbed in the time ( t) elapsed between t and t .
1 2 with 10.12.1 and 10.12.2 was employed, determine the time t
Calculate the weight of water vapor absorbed per hour (W).
t for the readout to span the calibrated increment corresponding
10.7 Insert a “perfect” barrier such as
to g for that range.
polytetrafluoroethylene-coated aluminum foil into the unit,
11.3.2 Record, purge, and repeat until time measured re-
aluminum to the humid side.
mains constant, that is, when t for repetitive cycles differs by
10.8 Repeat 10.4 through 10.6 allowing the test chamber to
no more than 65%.
purge for at least 48 h. Determine the weight of water vapor 11.3.3 Determine the WVTR of the sample from the equa-
absorbed (W ) from the dry air stream. This water vapor
tion in 10.12.2.
A
originates either from leaks in the system or incomplete drying
11.4 Determine the average thickness in accordance with
of the air stream. W should not exceed a few tenths of a 9.2.
A
milligram per hour.
10.9 Calculate the weight of water vapor transmitted by the 12. Report
standard barrier per hour (W ) by subtracting the water vapor
S 12.1 Report the following information:
absorbed from the dry air stream per hour (W ) from the total
A
12.1.1 Description of the barrier tested including identifica-
water vapor absorbed per hour (W).
t
tion of the two sides (if the barrier is homogeneous, so state),
10.10 Calculate the WVTR for the standard as follows:
12.1.2 Thickness of the specimen as determined in 11.4,
12.1.3 Temperature of the test and humid chambers,
WVTR 5 24 W /A
S
12.1.4 Relative humidity of the humid chambers, and
where:
12.1.5 WVTR of each specimen referencing which side of
WVTR = water vapor transmission rate at the temperature
the barrier, if heterogeneous, was in contact with the humid
and humidity used, g/m ·day,
chamber.
W = weight of water vapor transmitted, g/h, and
S
A = transmitting surface area of the standard, m .
13. Precision and Bias
10.11 Repeat several times and average the results. The
13.1 The precision of this test method was estimated from
standard deviation should not be greater than 65 % of the
the results of a round robin conducted in the early 1970’s.
average.
Eleven laboratories participated, six used Test Methods
10.12 Calibrate each range of the readout device for the
E96E96 and five used this test method, MoCon IRD-2 (see
water vapor sensor using the calibrated barrier standard in
Annex). Seven films between 1.0 and 3.6 mils thick were
conjunction with its WVTR as determined in 10.11.
tested, as follows:
10.12.1 This can be accomplished in a number of ways
No. 1—Single-side polyethylene-coated glassine
depending upon the readout device. If the readout device is an
No. 2—Two-side saran-coated glassine
ammeter, one of the methods that can be employed is to
No. 3—Nylon/polyethylene-nylon to the humid side of cham-
determine the time for the meter reading to increase a specific
ber
increment for each range.
No. 4—Nylon/polyethylene-polythylene to the humid side of
10.12.2 Calculate the weight of water vapor transmitted
chamber
through the barrier during that time as follows:
No. 5—Polyethylene
g5~WVTR! A t
~ ! ~ !
No. 6—Polylethylene terephthalate
No. 7—Rubber hydrochloride
where:
WVTR = WVTR of standard barrier under same tempera- NOTE 1—Glassine is a paper material.
ture and relative humidity condition as deter-
13.1.1 The data indicated that this test method and Test
mined in 10.11,
Methods E 96E96 yielded the same results with the new
A = surface area of sample interfacing test and hu-
method providing measurements in far less time and with
mid chamber(s).
better precision. This study and the data obtained are recorded
t = time for instrument to span the increment, and
in detail in STP 548 (1). These data were treated by the
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
F372–99
TABLE 1 Practice E 691E 691 – 79 Precision Summary for WVTR by IRD-2 (g/100 in. , 24 h at 100°F and 90 % Relative Humidity)
NOTE 1—The data is taken from ASTM STP 548.
NOTE 2—Material 2 appears to be nonuniform.
A B C D E F G H
¯
Material Number X Sr SL SR Vr VR Ir IR
1 0.928 0.0641 0.1148 0.1315 6.90 12.38 0.181 0.372
2 0.350 0.0504 0.1354 0.1445 14.40 38.69 0.143 0.409
3 0.334 0.0172 0.0380 0.0417 5.15 11.38 0.0487 0.118
4 0.290 0.0170 0.0185 0.0251 5.86 6.37 0.0481 0.0710
5 0.436 0.0137 0.0326 0.0353 3.14 7.48 0.0387 0.0999
6 1.348 0.0498 0.0954 0.1076 3.69 7.08 0.141 0.305
7 0.450 0.0383 0.0175 0.0421 8.51 3.89 0.108 0.119
Averages 6.81 12.47
Averages omitting Material 2 4.75 6.94
A
Laboratory averages, n=5.
B
Within-laboratory pooled standard deviation.
C
Between-laboratory standard deviation.
D
Between-laboratory variability estimate of precision.
E
Within-laboratory coefficient of variation.
F
Between-laboratory coefficient of variation.
G
95 % within-laboratory repeatability interval.
H
95 % between-laboratory reproducibility interval.
procedures in accordance with Practice E 691E 691 and data on the same materials from the two test methods. A
presented at a symposium in 1987. This treatment is recorded precision summary for Test Methods E 96E96 and a compari-
in STP1039. Table 1 is the currently recommended precision son of average WVTRs from the two test methods are in STP
summary for this test method. 1039. (2) They show no significant differences between aver-
13.2 Bias—SinceTest Methods E 96E96 were the accepted age rates obtained with the two test methods. Therefore, this
test methods for measuring WVTR when this test method was test method exhibits no bias with respect to Test Me
...