ASTM D2842-19

Standard Test Method for Water Absorption of Rigid Cellular Plastics

SIGNIFICANCE AND USE
5.1 The purpose of this test method is to provide a means for comparing relative water absorption tendencies between different cellular plastics. It is intended for use in specifications, product evaluation, and quality control. It is applicable to specific end-use design requirements only to the extent that the end-use conditions are similar to the immersion period (normally 96 h) and 5.1-cm (2-in.) head requirements of the test method.
Note 2: Studies by ASTM Subcommittee D20.22 show that some cellular plastics, particularly those with open cells or natural interstices, continue to absorb additional significant amounts of water beyond the 96-h immersion period. It was also found that water absorption of some cellular plastics is significantly higher when exposed to a greater pressure head, as might be encountered in certain underwater installations.  
5.2 This test method provides a means for measuring absorption as a result of direct contact exposure to free water. Results by this test method cannot be used to compare the resistance of cellular plastics to water vapor transmission and subsequent condensation within the cells. To determine resistance to water vapor transmission, see Test Methods E96.  
5.3 Water absorption testing is subject to several important variables, which if not considered, prohibit sufficient agreement among testing laboratories. Development of this test method has taken into account the most serious of the possible sources of error. See Notes 3-6, below, for some possible sources of error.
Note 3: In some methods, an error is encountered due to a rapid absorption of water before an accurate initial weight can be obtained. This test method accounts for that potential error by providing Procedure A for use with materials that behave in this manner. In this procedure the only submerged measurement required is a final weighing taken after the 96-h immersion period.
Note 4: The increase in volume that occurs with some foams when immers...
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 of 96 h.  
1.2 This test method describes two procedures that shall be used to measure the change in buoyant force. Procedure A shall 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 shall 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
Note 1: This test method is equivalent to ISO 2896.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Apr-2019
• ICS: 83.100 - Cellular materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.22 - Cellular Materials - Plastics and Elastomers

Relations

• Replaces: ASTM D2842-12 - Standard Test Method for Water Absorption of Rigid Cellular Plastics
• Effective Date: 01-May-2019
• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D4968-19a - Standard Practice for Annual Review of Test Methods and Specifications for Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D4968-19 - Standard Practice for Annual Review of Test Methods and Specifications for Plastics
• Effective Date: 01-May-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E2935-17 - Standard Practice for Conducting Equivalence Testing in Laboratory Applications
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017

Overview

ASTM D2842-19: Standard Test Method for Water Absorption of Rigid Cellular Plastics establishes a comprehensive procedure for determining the water absorption of rigid cellular plastics. This standard provides a consistent means of measuring the change in buoyant force of a plastic specimen after immersion under a specific head of water for a defined period. Developed by ASTM International, the test method is recognized for use in product specifications, quality control, and comparative product evaluation.

By standardizing the method for measuring water absorption, ASTM D2842-19 enables manufacturers, engineers, and end-users to reliably compare different cellular plastic products for use in environments where contact with water or moisture is a concern.

Key Topics

• Purpose and Scope: This test method is designed to compare the relative tendency of various rigid cellular plastics (such as foams and insulation boards) to absorb water when exposed to direct contact under specified conditions.

• Test Procedures: Two distinct procedures, A and B, are described:

  • Procedure A is used for cellular plastics that absorb water rapidly or increase in volume when wetted.
  • Procedure B applies to materials without rapid absorption or significant volume change.

• Test Conditions:

  • Immersion under a 5.1-cm (2-in.) head of water
  • Duration of 96 hours (other periods may be specified by agreement)
  • Measurement of volume change and dry/wet weight

• Measurement Accuracy: Emphasis is placed on surface preparation, specimen conditioning, removal of air bubbles, and careful weighing to minimize error.

• Interlaboratory Consistency: The method addresses common variables affecting test results and includes recommendations for ensuring reproducibility and reliability of water absorption measurements.

Applications

ASTM D2842-19 is widely used in industries where the performance of rigid cellular plastics in wet or humid environments is critical. Key applications include:

• Product Development and Specification: Assists manufacturers in designing rigid plastics with required water absorption properties, ensuring suitability for specific applications such as construction, transportation, and marine environments.

• Quality Control: Enables consistent monitoring of production batches to ensure compliance with water absorption requirements.

• Product Evaluation and Certification: Facilitates objective comparison of water absorption tendencies between different types, lots, or brands of rigid cellular plastics.

• Design Engineering: Supports decision-making for selecting the optimal plastic material for applications where moisture resistance is a primary or secondary performance characteristic.

• Regulatory Compliance: Provides a recognized testing methodology for meeting national and international standards in insulating panels, structural foams, flotation devices, and more.

Related Standards

Users of ASTM D2842-19 may also benefit from familiarity with these related standards:

• ASTM D3576: Test Method for Cell Size of Rigid Cellular Plastics
• ASTM E96: Test Methods for Water Vapor Transmission of Materials (for evaluating vapor transmission rather than direct water absorption)
• ASTM D883: Terminology Relating to Plastics
• ISO 2896: Cellular Plastics, Rigid-Determination of Water Absorption (method equivalency is acknowledged in the standard)
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

Keywords: ASTM D2842-19, water absorption, rigid cellular plastics, water absorption test, cellular plastic foam, plastic insulation testing, immersion testing, plastics quality control, ASTM standards for plastics, construction material testing

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D2842 − 19
Standard Test Method for
Water Absorption of Rigid Cellular Plastics
This standard is issued under the fixed designation D2842; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* D3576Test Method for Cell Size of Rigid Cellular Plastics
D4968Practice for Annual Review of Test Methods and
1.1 This test method covers the determination of the water
Specifications for Plastics
absorptionofrigidcellularplasticsbymeasuringthechangein
E96Test Methods for Water Vapor Transmission of Materi-
buoyant force resulting from immersion under a 5.1-cm (2-in.)
als
head of water for the specified immersion period of 96 h.
E177Practice for Use of the Terms Precision and Bias in
1.2 This test method describes two procedures that shall be
ASTM Test Methods
usedtomeasurethechangeinbuoyantforce.ProcedureAshall
E456Terminology Relating to Quality and Statistics
be used for materials that either experience rapid water
E691Practice for Conducting an Interlaboratory Study to
absorption or that show an increase in volume during the
Determine the Precision of a Test Method
exposureperiod,orboth.Materialsthatdonotexhibiteitherof
E2935 Practice for Conducting Equivalence Testing in
these characteristics shall be evaluated by Procedure B.
Laboratory Applications
1.3 For specific applications, immersion periods varying
2.2 ISO Standard:
from the normal 96-h test requirement shall be agreed upon
ISO2896 Cellular Plastics, Rigid—Determination of Water
between the manufacturer and the purchaser.
Absorption
1.4 The values stated in SI units are to be regarded as the
standard.
3. Terminology
1.5 This standard does not purport to address all of the
3.1 Definitions—Terms used in this standard are defined in
safety concerns, if any, associated with its use. It is the
accordance with Terminology D883, unless otherwise speci-
responsibility of the user of this standard to establish appro-
fied.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3.2 For terms relating to precision and bias and associated
issues,thetermsusedinthisstandardaredefinedinaccordance
NOTE 1—This test method is equivalent to ISO2896.
with Terminology E456.
1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
4. Summary of Test Method
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
4.1 The buoyant force of an object less dense than water is
mendations issued by the World Trade Organization Technical
equal to the weight of water it displaces when submerged, less
Barriers to Trade (TBT) Committee.
the dry weight of the object. Water absorbed into the object
2. Referenced Documents lowers the buoyant force by increasing the weight of the
sample. By knowing the volume and initial dry weight of the
2.1 ASTM Standards:
sample,theinitialbuoyantforcecanbecalculatedortheinitial
D883Terminology Relating to Plastics
buoyant force can be determined by direct measurement. The
1 final buoyant force at the end of the immersion period is
ThistestmethodisunderthejurisdictionofASTMCommitteeD20onPlastics
and is the direct responsibility of Subcommittee D20.22 on Cellular Materials -
measured with an underwater weighing assembly. The differ-
Plastics and Elastomers.
encebetweentheinitialandfinalbuoyantforceistheweightof
Current edition approved May 1, 2019. Published May 2019. Originally
the water absorbed per unit of specimen volume.
approved in 1969. Last previous edition approved in 2012 as D2842-12. DOI:
10.1520/D2842-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2842 − 19
5. Significance and Use specimens and the corresponding products are different, it is
possible that the test results will be misleading.
5.1 Thepurposeofthistestmethodistoprovideameansfor
5.6 In most cases water retention is a secondary perfor-
comparing relative water absorption tendencies between dif-
mance characteristic that has an influence on a primary
ferent cellular plastics. It is intended for use in specifications,
characteristic, such as thermal performance, surface accumu-
product evaluation, and quality control. It is applicable to
lation of moisture, localized collection of electrolytes, dimen-
specificend-usedesignrequirementsonlytotheextentthatthe
sional stability, etc.
end-use conditions are similar to the immersion period (nor-
mally 96 h) and 5.1-cm (2-in.) head requirements of the test
5.7 Before proceeding with this test method, reference shall
method.
be made to the specification of the material being tested. Any
test specimen preparation, conditioning, dimensions, or testing
NOTE 2—Studies by ASTM Subcommittee D20.22 show that some
parameters covered in the material specification shall take
cellular plastics, particularly those with open cells or natural interstices,
continue to absorb additional significant amounts of water beyond the
precedence over those mentioned in this test method. If there
96-h immersion period. It was also found that water absorption of some
are no material specifications, then the default conditions in
cellular plastics is significantly higher when exposed to a greater pressure
this standard shall apply.
head, as might be encountered in certain underwater installations.
6. Apparatus
5.2 This test method provides a means for measuring
absorption as a result of direct contact exposure to free water.
6.1 Balance—A balance capable of weighing up to 2500 g
Results by this test method cannot be used to compare the
with a sensitivity of 0.01 g. Balance must have a provision for
resistance of cellular plastics to water vapor transmission and
attaching a wire sling below the balance platform for taking
subsequent condensation within the cells. To determine resis-
submerged weight readings.
tance to water vapor transmission, see Test Methods E96.
6.2 Underwater Weighing Jig, constructed so that specimen
5.3 Water absorption testing is subject to several important
floats against jig ceiling with 15.2 by 15.2-cm (6 by 6-in.)
variables, which if not considered, prohibit sufficient agree-
specimen face in the horizontal position. The jig shall trap no
ment among testing laboratories. Development of this test
airwhensubmerged.Theapproximatedryweightistobe2500
method has taken into account the most serious of the possible
g. Fig. 1 shows two recommended styles of jig construction.
sources of error. See Notes 3-6, below, for some possible
6.3 Immersion Tank—An open-top tank or aquarium of
sources of error.
sufficient size to accommodate at least three specimens with
NOTE 3—In some methods, an error is encountered due to a rapid the top 15.2 by 15.2-cm (6 by 6-in.) faces in the horizontal
absorptionofwaterbeforeanaccurateinitialweightcanbeobtained.This
position and additional space for the weighing jig. (A75.8-dm
test method accounts for that potential error by providing ProcedureAfor
(20-gal) glass aquarium, 76.2 by 33.0 by 30.5 cm (30 by 13 by
use with materials that behave in this manner. In this procedure the only
12in.)highisofsufficientsizefortestinguptosixspecimens.)
submerged measurement required is a final weighing taken after the 96-h
immersion period.
6.4 Balance Platform—A mounting platform to be placed
NOTE 4—The increase in volume that occurs with some foams when
across the top of the immersion tank to support the balance.A
immersed is accounted for in Procedure A. This procedure shall be used
hole in the platform must be provided at an appropriate
for materials that exhibit this type of behavior. This is accounted for by
location to accommodate wire sling from balance to jig.
basing all buoyant force calculations on the volume of the wet specimen
at the conclusion of the immersion period.
6.5 Conditioning Oven—Forced-air circulating oven ca-
NOTE 5—The problem of air bubbles clinging to the submerged
pable of maintaining 50 6 3°C (122 6 5°F) for 24 h.
specimen and affecting the end result is minimized by specifying
deaerated distilled water.
6.6 Desiccator, containing desiccant with high affinity for
NOTE 6—Surface cells opened during specimen preparation result in an
water vapor (anhydrous calcium chloride or equivalent) for
error when calculating the apparent volume of the test specimen. The
maintaining dryness of test specimens upon removal from
degreeofthiserrorisafunctionofcellsize.Thistestmethodaccountsfor
conditioning oven.
this error in that all calculations are based on the true specimen volume.
The true specimen volume is determined in ProcedureAas the measured
6.7 Vernier Calipers or Dial Micrometer—Measuring de-
volume minus the volume of surface cells opened by cutting. This
vicecapableofmeasuringspecimentonearest0.002cm(0.001
correction is not required in Procedure B since the true specimen volume
in.). Fig. 2 shows a recommended measuring device.
is determined by direct measurement.
6.8 Cell-Size Specimen Slicer—Cutting blade apparatus ca-
5.4 The volume error associated with surface cells opened
pable of slicing thin specimens (0.01 to 0.04 cm) for cell size
during specimen preparation decreases as the cell size de-
viewing. Fig. 3 shows an acceptable alternative slicing appa-
creases. This test method provides the option to ignore this
ratus.
variable with cellular plastics that have an average cell
diameterof0.03cmorless.Forcellularplasticshavinggreater
6.9 Cell-Size Projector—Conventional 35-mm slide projec-
than 0.03-cm average cell diameter and in all cases of dispute,
tor that accepts standard 5.1 by 5.1-cm (2 by 2-in.) slides. See
measurementofcellsizeshallbemandatoryindeterminingthe
Note 7.
specimen volume.
6.10 Cell-Size Scale Slide Assembly, consisting of two
5.5 For most materials, the size of the test specimens is pieces of slide glass hinged by tape along one edge, between
small compared with the size of the products actually installed which a calibrated scale (3.0 cm in length) printed on a thin
in the field. If the surface-to-volume ratios for the test plastic sheet is placed. See Fig. 4.
D2842 − 19
FIG. 1 Underwater Weighing Jigs
NOTE 7—Microscopic or digital imaging techniques for measuring
7.2 Gas Barrier Film—Layer of low permeance plastic film
cell-sizes can be suitable replacements for the technique described in this
(polyethylene, food wrap, or equivalent) covering surface of
standard.SeeTestMethodD3576fordetailsonthetechniquedescribedin
water to retard air pick up by deaerated water.
this standard.
7. Reagents and Materials
8. Test Specimens
7.1 Distilled Water—Sufficient amount of freshly distilled
8.1 Three test specimens shall be tested from each sample.
water to maintain a 5.1-cm (2-in.) head over specimens and jig
8.2 Test Specimen Size:
at all times.
D2842 − 19
FIG. 2 Dual-Dial Micrometer Measuring Device
8.2.1 Therecommendedtestspecimensizeshallbe15.2cm skinsurfacesandforothermaterialsinwhichthesamplestock
(6 in.) in width by 15.2 cm in length by 7.6 cm (3 in.) in available for testing is less than 7.6 cm in thickness.
thickness for any material which can be cut to this size from 8.2.3 For materials produced and sold with natural or
larger stock without substantially changing its original charac- laminated skin surfaces having an overall thickness greater
ter. than 7.6 cm (3 in.), the test specimen thickness shall be the
8.2.2 Testspecimensizeshallbe15.2cm(6in.)inwidthby actual thickness with the length and width dimensions in-
15.2cminlengthbytheactualthicknessesformaterialshaving creased to no less than two times the thickness dimension. To
less than 7.6 cm (3 in.) overall thickness. This is intended for accommodatetheselargerspecimens,thetestequipmentspeci-
materialsnormallyproducedandsoldwithnaturalorlaminated fied previously must be modified accordingly.
D2842 − 19
FIG. 3 Razor Blade Cell-Size Specimen Slicer
FIG. 4 Cell-Size Scale Slide Assembly
8.3 Test specimens shall be machined or sawed from the or sanding with No. 0 or finer sandpaper. Resulting dust shall
sample so that they have smooth surfaces. All machined or
be removed from the specimen.
sawedsurfacesshallbefurthersmoothedbyslicingtechniques
D2842 − 19
9. Conditioning so that shadowgraph will not be occluded by overlapping cell
walls. Optimum slice thickness will vary with the average cell
9.1 Unless specified by the contract or relevant material
size of the foam with larger cell foams requiring thicker slices.
specification, after cutting specimens, condition them in a
forced-air circulating oven for 24 h or more at 50 6 3°C (122
NOTE 8—One cell-size measurement will provide a representative
6 5°F). average cell size for cellular plastics having symmetric cells of relatively
uniform size. However, cellular plastics known to be significantly aniso-
9.2 Allow specimens to cool to room temperature in a
tropic will require measurement of cell size in three normal directions for
desiccator and then weigh to the nearest 0.01 g.
maximum accuracy. An acceptable procedure, in this case, is to take
cell-size slices from two perpendicular planes of the test specimen. The
9.3 Return specimens to conditioning oven for 4 additional
size of the cells in the three normal directions can then be measured to
hours at 50 6 3°C (122 6 5°F), cool in desiccator, and weigh
fully represent the cell.
to the nearest 0.01 g. Repeat 4-h conditioning intervals until
10.1.13 Insert the thin-sliced foam specimen into the cell-
specimens reach constant weight as indicated by less than
size slide “sandwich” assembly. Position the zero on the grid
0.01-g weight change between successive weighings.
lineatthetopoftheareatobemeasured.Reassembletheslide.
9.4 Recordfinaldrywei
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D2842 − 12 D2842 − 19
Standard Test Method for
Water Absorption of Rigid Cellular Plastics
This standard is issued under the fixed designation D2842; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. 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 of 96 h.
1.2 This test method describes two procedures that shall be used to measure the change in buoyant force. Procedure A shall 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 shall 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
NOTE 1—This test method is equivalent to ISO 2896.
NOTE 1—This test method is equivalent to ISO 2896.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
D3576 Test Method for Cell Size of Rigid Cellular Plastics
D4968 Practice for Annual Review of Test Methods and Specifications for Plastics
E96 Test Methods for Water Vapor Transmission of Materials
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E2935 Practice for Conducting Equivalence Testing in Laboratory Applications
2.2 ISO Standard:
ISO 2896 Cellular Plastics, Rigid—Determination of Water Absorption
3. Terminology
3.1 Definitions—There are no terms in this test method that are new or other than dictionary definitions.
3.1 Definitions—Terms used in this standard are defined in accordance with Terminology D883, unless otherwise specified.
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.22 on Cellular Materials - Plastics
and Elastomers.
Current edition approved Oct. 1, 2012May 1, 2019. Published November 2012May 2019. Originally approved in 1969. Last previous edition approved in 20062012 as
D2842 - 06.D2842 - 12. DOI: 10.1520/D2842-12.10.1520/D2842-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2842 − 19
3.2 For terms relating to precision and bias and associated issues, the terms used in this standard are defined in accordance with
Terminology E456.
4. Summary of Test Method
4.1 The buoyant force of an object less dense than water is equal to the weight of water it displaces when submerged, less the
dry weight of the object. Water absorbed into the object lowers the buoyant force by increasing the weight of the sample. By
knowing the volume and initial dry weight of the sample, the initial buoyant force can be calculated or the initial buoyant force
can be determined by direct measurement. The final buoyant force at the end of the immersion period is measured with an
underwater weighing assembly. The difference between the initial and final buoyant force is the weight of the water absorbed per
unit of specimen volume.
5. Significance and Use
5.1 The purpose of this test method is to provide a means for comparing relative water absorption tendencies between different
cellular plastics. It is intended for use in specifications, product evaluation, and quality control. It is applicable to specific end-use
design requirements only to the extent that the end-use conditions are similar to the immersion period (normally 96 h) and 5.1-cm
(2-in.) head requirements of the test method.
NOTE 2—Studies by ASTM Subcommittee D20.22 show that some cellular plastics, particularly those with open cells or natural interstices, continue
to absorb additional significant amounts of water beyond the 96-h immersion period. It was also found that water absorption of some cellular plastics
is significantly higher when exposed to a greater pressure head, as might be encountered in certain underwater installations.
5.2 This test method provides a means for measuring absorption as a result of direct contact exposure to free water. Results by
this test method cannot be used to compare the resistance of cellular plastics to water vapor transmission and subsequent
condensation within the cells. To determine resistance to water vapor transmission, see Test Methods E96.
5.3 Water absorption testing is subject to several important variables, which if not considered, prohibit sufficient agreement
among testing laboratories. Development of this test method has taken into account the most serious of the possible sources of
error. See Notes 3-6, below, for some possible sources of error.
NOTE 3—In some methods, an error is encountered due to a rapid absorption of water before an accurate initial weight can be obtained. This test method
accounts for that potential error by providing Procedure A for use with materials that behave in this manner. In this procedure the only submerged
measurement required is a final weighing taken after the 96-h immersion period.
NOTE 4—The increase in volume that occurs with some foams when immersed is accounted for in Procedure A. This procedure shall be used for
materials that exhibit this type of behavior. This is accounted for by basing all buoyant force calculations on the volume of the wet specimen at the
conclusion of the immersion period.
NOTE 5—The problem of air bubbles clinging to the submerged specimen and affecting the end result is minimized by specifying deaerated distilled
water.
NOTE 6—Surface cells opened during specimen preparation result in an error when calculating the apparent volume of the test specimen. The degree
of this error is a function of cell size. This test method accounts for this error in that all calculations are based on the true specimen volume. The true
specimen volume is determined in Procedure A as the measured volume minus the volume of surface cells opened by cutting. This correction is not
required in Procedure B since the true specimen volume is determined by direct measurement.
5.4 The volume error associated with surface cells opened during specimen preparation decreases as the cell size decreases. This
test method provides the option to ignore this variable with cellular plastics that have an average cell diameter of 0.03 cm or less.
For cellular plastics having greater than 0.03-cm average cell diameter and in all cases of dispute, measurement of cell size shall
be mandatory in determining the specimen volume.
5.5 For most materials, the size of the test specimens is small compared with the size of the products actually installed in the
field. If the surface-to-volume ratios for the test specimens and the corresponding products are different, it is possible that the test
results are will be misleading.
5.6 In most cases water retention is a secondary performance characteristic that has an influence on a primary characteristic,
such as thermal performance, surface accumulation of moisture, localized collection of electrolytes, dimensional stability, etc.
5.7 Before proceeding with this test method, reference shall be made to the specification of the material being tested. Any test
specimen preparation, conditioning, dimensions, or testing parameters covered in the materials specification, or both, material
specification shall take precedence over those mentioned in this test method. If there are no material specifications, then the default
conditions in this standard shall apply.
6. Apparatus
6.1 Balance—A balance capable of weighing up to 2500 g with a sensitivity of 0.01 g. Balance must have a provision for
attaching thea wire sling below the balance platform for makingtaking submerged weighings.weight readings.
6.2 Underwater Weighing Jig, constructed so that specimen floats against jig ceiling with 15.2 by 15.2-cm (6 by 6-in.) specimen
face in the horizontal position. The jig shall trap no air when submerged. The approximate dry weight is to be 2500 g. Fig. 1 shows
two recommended styles of jig construction.
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FIG. 1 Underwater Weighing Jigs
6.3 Immersion Tank—An open-top tank or aquarium of sufficient size to accommodate at least three specimens with the top 15.2
by 15.2-cm (6 by 6-in.) faces in the horizontal position and additional space for the weighing jig. (A 75.8-dm (20-gal) glass
aquarium, 76.2 by 33.0 by 30.430.5 cm (30 by 13 by 12 in.) high is of sufficient size for testing up to six specimens.)
6.4 Balance Platform—A mounting platform to be placed across the top of the immersion tank to support the balance. A hole
in the platform must be provided at an appropriate location to accommodate wire sling from balance to jig.
6.5 Conditioning Oven—Forced-air circulating oven capable of maintaining 50 6 3°C (122 6 5°F) for 24 h.
6.6 Desiccator, containing desiccant with high affinity for water vapor (anhydrous calcium chloride or equivalent) for
maintaining dryness of test specimens upon removal from conditioning oven.
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FIG. 2 Dual-Dial Micrometer Measuring Device
6.7 Vernier Calipers or Dial Micrometer—Measuring device capable of measuring specimen to nearest 0.002 cm (0.001 in.).
Fig. 2 shows a recommended measuring device.
6.8 Cell-Size Specimen Slicer—Cutting blade apparatus capable of slicing thin specimens (0.01 to 0.04 cm) for cell size viewing.
Fig. 3 shows an acceptable alternative slicing apparatus.
6.9 Cell-Size Projector—Conventional 35-mm slide projector that accepts standard 5.1 by 5.1-cm (2 by 2-in.) slides. See Note
7.
6.10 Cell-Size Scale Slide Assembly, consisting of two pieces of slide glass hinged by tape along one edge, between which a
calibrated scale (3.0 mmcm in length) printed on a thin plastic sheet is placed. See Fig. 4.
NOTE 7—Microscopic or digital imaging techniques for measuring cell-sizes can be suitable replacements for the technique described in this standard.
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FIG. 3 Razor Blade Cell-Size Specimen Slicer
FIG. 4 Cell-Size Scale Slide Assembly
See Test Method D3576 for details on the technique described in this standard.
7. Reagents and Materials
7.1 Distilled Water—Sufficient amount of freshly distilled water to maintain a 5.08-cm5.1-cm (2-in.) head over specimens and
jig at all times.
7.2 Gas Barrier Film—Layer of low permeance (polyethylene, saran, plastic film (polyethylene, food wrap, or equivalent)
plastic film covering surface of water to retard air pick up by deaerated water.
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8. Test Specimens
8.1 Three test specimens shall be tested from each sample.
8.2 Test Specimen Size:
8.2.1 The recommended test specimen size shall be 1515.2 cm (6 in.) in width by 1515.2 cm in length by 7.57.6 cm (3 in.) in
thickness for any material which can be cut to this size from larger stock without substantially changing its original character.
8.2.2 Test specimen size shall be 1515.2 cm (6 in.) in width by 1515.2 cm in length by the actual thicknesses for materials
having less than 7.57.6 cm (3 in.) overall thickness. This is intended for materials normally produced and sold with natural or
laminated skin surfaces and for other materials in which the sample stock available for testing is less than 7.57.6 cm in thickness.
8.2.3 For materials produced and sold with natural or laminated skin surfaces having an overall thickness greater than 7.57.6
cm (3 in.), the test specimen thickness shall be the actual thickness with the length and width dimensions increased to no less than
two times the thickness dimension. To accommodate these larger specimens, the test equipment specified previously must be
modified accordingly.
8.3 Test specimens shall be machined or sawed from the sample so that they have smooth surfaces. All machined or sawed
surfaces shall be further smoothed by slicing techniques or sanding with No. 0 or finer sandpaper. Resulting dust shall be removed
from the specimen.
9. Conditioning
9.1 Unless specified by the contract or relevant material specification, after cutting specimens, condition them in a forced-air
circulating oven for 24 h or more at 50 6 3°C (122 6 5°F).
9.2 Allow specimens to cool to room temperature in a desiccator and then weigh to the nearest 0.01 g.
9.3 Return specimens to conditioning oven for 4 additional hours at 50 6 3°C (122 6 5°F), cool in desiccator, and weigh to
the nearest 0.10.01 g. Repeat 4-h conditioning intervals until specimens reach constant weight as indicated by less than 0.1-g0.01-g
weight change between successive weighings.
9.4 Record final dry weight of each specimen to nearest 0.01 g (W ).
10. Procedure
10.1 Procedure A:
10.1.1 Place underwater weighing jig in immersion tank.
10.1.2 Immerse specimens by suitable weighted rack in open-top immersion tank filled with freshly distilled water at 23 6 2°C
(73.4 6 3.6°F). Adjust the water level to maintain a 5.1-cm (2-in.) head of water over the top of specimens with 15.2 by 15.2-cm
(6 by 6-in.) faces in the horizontal position.
10.1.3 Remove obvious air bubbles clinging to the specimen with a soft-bristle brush.
10.1.4 Cover entire surface of water with low-permeance plastic film.
10.1.5 Leave specimens immersed for 96 h while maintaining 5.1-cm (2-in.) head of water at 23 6 2°C (73.4 6 3.6°F).
10.1.6 At the end of 96-h immersion time, assemble balance platform and balance on the top of the tank, remove the plastic
film from water, and zero balance.
10.1.7 Attach the underwater weighing jig to the balance with wire sling, such that the top horizontal surface of the jig is 5.1
cm (2 in.) below the surface of the water. Be sure Ensure that the submerged jig is free of trapped air bubbles.
10.1.8 Weigh the empty submerged jig to the nearest 0.010.1 g (W ).
10.1.9 Insert the test specimen into submerged underwater weighing jig without removing the specimen from the water. Weigh
to the nearest 0.10.01 g (W ). Do not remove any specimens from the water until all have been weighed, as removing the specimens
reduces the 5.1-cm (2-in.) head.
10.1.10 Remove specimens from water and immediately measure the specimen dimensions (length, width, and thickness) to the
nearest 0.002 cm (0.001 in.). For convenience, remov
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