ASTM D2842-97
(Test Method)Standard Test Method for Water Absorption of Rigid Cellular Plastics
Standard Test Method for Water Absorption of Rigid Cellular Plastics
SCOPE
1.1 This test method covers the determination of the water absorption of rigid cellular plastics by measuring the change in buoyant force resulting from immersion under a 5.1-cm (2-in.) head of water for the specified immersion period for 96 h is standard.
1.2 This test method describes two procedures that may be used to measure the change in buoyant force. Procedure A should be used for materials that either experience rapid water absorption or that show an increase in volume during the exposure period, or both. Materials that do not exhibit either of these characteristics should be evaluated by Procedure B.
1.3 For specific applications, immersion periods varying from the normal 96-h test requirement shall be agreed upon between the manufacturer and the purchaser.
1.4 The values stated in SI units are to be regarded as the standard.
1.5 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.
Note 1—This test method and ISO 2896 are technically equivalent.
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Designation: D 2842 – 97 An American National Standard
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Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Water Absorption of Rigid Cellular Plastics
This standard is issued under the fixed designation D 2842; 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.
1. Scope * are new or other than dictionary definitions.
1.1 This test method covers the determination of the water
4. Summary of Test Method
absorption of rigid cellular plastics by measuring the change in
4.1 The buoyant force of an object less dense than water is
buoyant force resulting from immersion under a 5.1-cm (2-in.)
equal to the weight of water it displaces when submerged, less
head of water for the specified immersion period of 96 h.
the dry weight of the object. Water absorbed into the object
1.2 This test method describes two procedures that may be
lowers the buoyant force by increasing the weight of the
used to measure the change in buoyant force. Procedure A
sample. By knowing the volume and initial dry weight of the
should be used for materials that either experience rapid water
sample, the initial buoyant force can be calculated or the initial
absorption or that show an increase in volume during the
buoyant force can be determined by direct measurement. The
exposure period, or both. Materials that do not exhibit either of
final buoyant force at the end of the immersion period is
these characteristics should be evaluated by Procedure B.
measured with an underwater weighing assembly. The differ-
1.3 For specific applications, immersion periods varying
ence between the initial and final buoyant force is the weight of
from the normal 96-h test requirement shall be agreed upon
the water absorbed per unit of specimen volume.
between the manufacturer and the purchaser.
1.4 The values stated in SI units are to be regarded as the
5. Significance and Use
standard.
5.1 The purpose of this test method is to provide a means for
1.5 This standard does not purport to address all of the
comparing relative water absorption tendencies between dif-
safety concerns, if any, associated with its use. It is the
ferent cellular plastics. It is intended for use in specifications,
responsibility of the user of this standard to establish appro-
product evaluation, and quality control. It is applicable to
priate safety and health practices and determine the applica-
specific end-use design requirements only to the extent that the
bility of regulatory limitations prior to use.
end-use conditions are similar to the immersion period (nor-
NOTE 1—This test method and ISO 2896 are technically equivalent.
mally 96 h) and 5.1-cm (2-in.) head requirements of the test
method.
2. Referenced Documents
NOTE 2—Studies by ASTM Subcommittee D20.22 show that some
2.1 ASTM Standards:
cellular plastics, particularly those with open cells or natural interstices,
D 3576 Test Method for Cell Size of Rigid Cellular Plas-
continue to absorb additional significant amounts of water beyond the
tics
96-h immersion period. It was also found that water absorption of some
E 96 Test Methods for Water Vapor Transmission of Mate-
cellular plastics is significantly higher when exposed to a greater pressure
rials
head, as might be encountered in certain underwater installations.
E 691 Practice for Conducting an Interlaboratory Study to
5.2 This test method provides a means for measuring
Determine the Precision of a Test Method
absorption as a result of direct contact exposure to free water.
2.2 ISO Standard:
Results by this test method cannot be used to compare the
ISO 2896 Cellular Plastics, Rigid—Determination of Water
resistance of cellular plastics to water vapor transmission and
Absorption
subsequent condensation within the cells. To determine resis-
tance to water vapor transmission, see Test Methods E 96.
3. Terminology
5.3 Water absorption testing is subject to several important
3.1 Definitions—There are no terms in this test method that
variables, which if not considered, prohibit sufficient agree-
ment among testing laboratories. Development of this test
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics
method has taken into account the most serious of the possible
and is the direct responsibility of Subcommittee D20.22 on Cellular Plastics.
sources of error.
Current edition approved Nov. 10, 1997. Published April 1998. Originally
published as D 2842 – 69. Last previous edition D 2842 – 94.
NOTE 3—In some methods, an error is encountered due to a rapid
Annual Book of ASTM Standards, Vol 08.02.
absorption of water before an accurate initial weight can be obtained. This
Annual Book of ASTM Standards, Vol 04.06.
test method accounts for that potential error by providing Procedure A for
Annual Book of ASTM Standards, Vol 14.02.
Available from American National Standards Institute, 11 W. 42nd St., 13th use with materials that behave in this manner. In this procedure the only
Floor, New York, NY 10036.
*A Summary of Changes section appears at the end of this standard.
D 2842
submerged measurement required is a final weighing taken after the 96-h
position and additional space for the weighing jig. (A 75.8-dm
immersion period.
(20-gal) glass aquarium, 76.2 by 33.0 by 30.4 cm (30 by 13 by
NOTE 4—The increase in volume that occurs with some foams when
12 in.) high is of sufficient size for testing up to six specimens.)
immersed is accounted for in Procedure A. This procedure should be used
6.4 Balance Platform—A mounting platform to be placed
for materials that exhibit this type of behavior. This is accounted for by
across the top of the immersion tank to support the balance. A
basing all buoyant force calculations on the volume of the wet specimen
hole in the platform must be provided at an appropriate
at the conclusion of the immersion period.
NOTE 5—The problem of air bubbles clinging to the submerged location to accommodate wire sling from balance to jig.
specimen and affecting the end result is minimized by specifying
6.5 Conditioning Oven—Forced-air circulating oven ca-
deaerated distilled water.
pable of maintaining 50 6 3°C (122 6 5°F) for 24 h.
NOTE 6—Surface cells opened during specimen preparation result in an
6.6 Desiccator, containing desiccant with high affinity for
error when calculating the apparent volume of the test specimen. The
water vapor (anhydrous calcium chloride or equivalent) for
degree of this error is a function of cell size. This test method accounts for
maintaining dryness of test specimens upon removal from
this error in that all calculations are based on the true specimen volume.
conditioning oven.
The true specimen volume is determined in Procedure A as the measured
volume minus the volume of surface cells opened by cutting. This
6.7 Vernier Calipers or Dial Micrometer—Measuring de-
correction is not required in Procedure B since the true specimen volume
vice capable of measuring specimen to nearest 0.002 cm (0.001
is determined by direct measurement.
in.). Fig. 2 shows a recommended measuring device.
5.4 The volume error associated with surface cells opened 6.8 Cell-Size Specimen Slicer —Cutting blade apparatus
during specimen preparation decreases as the cell size de- capable of slicing thin specimens (0.01 to 0.04 cm) for cellsize
creases. This test method provides the option to ignore this viewing. Fig. 3 shows an acceptable alternative slicing appa-
variable with cellular plastics estimated to have an average cell ratus.
diameter of 0.03 cm or less. For cellular plastics having greater 6.9 Cell-Size Projector—Conventional 35-mm slide pro-
than 0.03-cm average cell diameter and in all cases of dispute, jector that accepts standard 5.1 by 5.1-cm (2 by 2-in.) slides.
measurement of cell size shall be mandatory in determining the 6.10 Cell-Size Scale Slide Assembly, consisting of two
specimen volume. pieces of slide glass hinged by tape along one edge, between
5.5 For most materials the size of the test specimens is small which a calibrated scale (3.0 mm in length) printed on a thin
compared with the size of the products actually installed in the plastic sheet is placed. See Fig. 4.
field. If the surface-to-volume ratios for the test specimens and
7. Reagents and Materials
the corresponding products are different, the test results may be
7.1 Distilled Water—Sufficient amount of freshly distilled
misleading.
water to maintain a 5.08-cm (2-in.) head over specimens and
5.6 In most cases water retention is a secondary perfor-
jig at all times.
mance characteristic that has an influence on a primary
7.2 Gas Barrier Film—Layer of low permeance (polyeth-
characteristic, such as thermal performance, surface accumu-
ylene, saran, or equivalent) plastic film covering surface of
lation of moisture, localized collection of electrolytes, etc.
water to retard air pick up by deaerated water.
5.7 Before proceeding with this test method, reference
should be made to the specification of the material being tested.
8. Test Specimens
Any test specimen preparation, conditioning, dimensions, or
8.1 Three test specimens shall be tested from each sample.
testing parameters covered in the materials specification, or
8.2 Test Specimen Size:
both, shall take precedence over those mentioned in this test
8.2.1 The recommended test specimen size shall be 15 cm
method. If there are no material specifications, then the default
(6 in.) in width by 15 cm in length by 7.5 cm (3 in.) in
conditions apply.
thickness for any material which can be cut to this size from
larger stock without substantially changing its original charac-
6. Apparatus
ter.
6.1 Balance—A balance capable of weighing up to 2500 g
8.2.2 Test specimen size shall be 15 cm (6 in.) in width by
with a sensitivity of 0.1 g. Balance must have provision for
15 cm in length by the actual thicknesses for materials having
attaching wire sling below balance platform for making sub-
less than 7.5 cm (3 in.) overall thickness. This is intended for
merged weighings.
materials normally produced and sold with natural or laminated
6.2 Underwater Weighing Jig, constructed so that specimen
skin surfaces and for other materials in which the sample stock
floats against jig ceiling with 15.2 by 15.2-cm (6 by 6-in.)
available for testing is less than 7.5 cm in thickness.
specimen face in the horizontal position. The jig should trap no
8.2.3 For materials produced and sold with natural or
air when submerged. The approximate dry weight is to be 2500
laminated skin surfaces having an overall thickness greater
g. Fig. 1 shows two recommended styles of jig construction.
than 7.5 cm (3 in.), the test specimen thickness shall be the
6.3 Immersion Tank—An open-top tank or aquarium of
actual thickness with the length and width dimensions in-
sufficient size to accommodate at least three specimens with
creased to no less than two times the thickness dimension. To
the top 15.2 by 15.2-cm (6 by 6-in.) faces in the horizontal
Hobart Model 411, an electrically operated slicer available from the Hobart
Manufacturing Co., 12750 North End, Oak Park, MI 48237, has been found
satisfactory for this purpose.
Cell-size grid decals can be obtained from ASTM Headquarters, Reference Test
Method D 3576.
D 2842
FIG. 1 Underwater Weighing Jigs
accommodate these larger specimens, the test equipment speci- specification, after cutting specimens, condition them in a
fied previously must be modified accordingly.
forced-air circulating oven for 24 h or more at 50 6 3°C (122
8.3 Test specimens shall be machined or sawed from the
6 5°F).
sample so as to have smooth surfaces. All machined or sawed
9.2 Allow specimens to cool to room temperature in a
surfaces may be further smoothed by slicing techniques or
desiccator and then weigh to the nearest 0.1 g.
sanding with No. 0 or finer sandpaper. Resulting dust shall be
9.3 Return specimens to conditioning oven for 4 additional
blown from the specimen.
hours at 50 6 3°C (122 6 5°F), cool in desiccator, and weigh
9. Conditioning
to the nearest 0.1 g. Repeat 4-h conditioning intervals until
specimens reach constant weight as indicated by less than 0.2-g
9.1 Unless specified by the contract or relevant material
D 2842
FIG. 2 Dual-Dial Micrometer Measuring Device
weight change between successive weighings. 5.1-cm (2-in.) head of water over the top of specimens with
9.4 Record final dry weight of each specimen to nearest 0.1 15.2 by 15.2-cm (6 by 6-in.) faces in the horizontal position.
g(W ). 10.1.3 Remove obvious air bubbles clinging to the speci-
men with a soft-bristle brush.
10. Procedure
10.1.4 Cover entire surface of water with low-permeance
10.1 Procedure A: plastic film.
10.1.5 Leave specimens immersed for 96 h while maintain-
10.1.1 Place underwater weighing jig in immersion tank.
10.1.2 Immerse specimens by suitable weighted rack in ing 5.1-cm (2-in.) head of water at 23 6 2°C (73.4 6 3.6°F).
open-top immersion tank filled with freshly distilled water at 10.1.6 At the end of 96-h immersion time, assemble balance
23 6 2°C (73.4 6 3.6°F). Adjust the water level to maintain a platform and balance on the top of the tank, remove the plastic
D 2842
FIG. 3 Razor Blade Cell-Size Specimen Slicer
FIG. 4 Cell-Size Scale Slide Assembly
film from water, and zero balance. weighing jig without removing the specimen from the water.
10.1.7 Attach the underwater weighing jig to the balance
Weigh to the nearest 0.1 g (W ). Do not remove any specimens
with wire sling such that the top horizontal surface of the jig is
from the water until all have been weighed, as removing the
5.1 cm (2 in.) below the surface of the water. Be sure that the
specimens reduces the 5.1-cm (2-in.) head.
submerged jig is free of trapped air bubbles.
10.1.10 Remove specimens from water and immediately
10.1.8 Weigh the empty submerged jig to the nearest 0.1 g
measure the specimen dimensions (length, width, and thick-
(W ).
ness) to the nearest 0.002 cm (0.001 in.). For convenience,
10.1.9 Insert the test specimen into submerged underwater
D 2842
remove the surface water from the specimen with a towel immersion period (96 h is standard) while maintaining a
before measuring. 5.1-cm (2-in.) head of water at 23 6 2°C (73.
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