ASTM D570-98(2010)e1

Standard Test Method for Water Absorption of Plastics

SIGNIFICANCE AND USE
This test method for rate of water absorption has two chief functions: first, as a guide to the proportion of water absorbed by a material and consequently, in those cases where the relationships between moisture and electrical or mechanical properties, dimensions, or appearance have been determined, as a guide to the effects of exposure to water or humid conditions on such properties; and second, as a control test on the uniformity of a product. This second function is particularly applicable to sheet, rod, and tube arms when the test is made on the finished product.
Comparison of water absorption values of various plastics can be made on the basis of values obtained in accordance with 7.1 and 7.4.
Ideal diffusion of liquids into polymers is a function of the square root of immersion time. Time to saturation is strongly dependent on specimen thickness. For example, Table 1 shows the time to approximate time saturation for various thickness of nylon-6.
The moisture content of a plastic is very intimately related to such properties as electrical insulation resistance, dielectric losses, mechanical strength, appearance, and dimensions. The effect upon these properties of change in moisture content due to water absorption depends largely on the type of exposure (by immersion in water or by exposure to high humidity), shape of the part, and inherent properties of the plastic. With nonhomogeneous materials, such as laminated forms, the rate of water absorption may be widely different through each edge and surface. Even for otherwise homogeneous materials, it may be slightly greater through cut edges than through molded surfaces. Consequently, attempts to correlate water absorption with the surface area must generally be limited to closely related materials and to similarly shaped specimens: For materials of widely varying density, relation between water-absorption values on a volume as well as a weight basis may need to be considered.
SCOPE
1.1 This test method covers the determination of the relative rate of absorption of water by plastics when immersed. This test method is intended to apply to the testing of all types of plastics, including cast, hot-molded, and cold-molded resinous products, and both homogeneous and laminated plastics in rod and tube form and in sheets 0.13 mm [0.005 in.] or greater in thickness.  
1.2 The values given in SI units are to be regarded as standard. The values stated in brackets are for information only.  
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.
Note 1—ISO 62 is technically equivalent to this test method.

General Information

• Status: Historical
• Publication Date: 31-Mar-2010
• ICS: 83.120 - Reinforced plastics
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.50 - Durability of Plastics

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: D570 − 98 (Reapproved 2010)
Standard Test Method for
Water Absorption of Plastics
This standard is issued under the fixed designation D570; 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 Department of Defense.
´ NOTE—Removed ASTM D647 as a referenced document editorially in June 2010.
1. Scope larly applicable to sheet, rod, and tube arms when the test is
made on the finished product.
1.1 Thistestmethodcoversthedeterminationoftherelative
rate of absorption of water by plastics when immersed. This 3.2 Comparison of water absorption values of various plas-
test method is intended to apply to the testing of all types of tics can be made on the basis of values obtained in accordance
plastics, including cast, hot-molded, and cold-molded resinous with 7.1 and 7.4.
products, and both homogeneous and laminated plastics in rod 3
3.3 Ideal diffusion of liquids into polymers is a function of
and tube form and in sheets 0.13 mm (0.005 in.) or greater in
the square root of immersion time. Time to saturation is
thickness.
strongly dependent on specimen thickness. For example, Table
1.2 The values given in SI units are to be regarded as 1 shows the time to approximate time saturation for various
standard. The values stated in parentheses are for information thickness of nylon-6.
only.
3.4 The moisture content of a plastic is very intimately
1.3 This standard does not purport to address all of the
related to such properties as electrical insulation resistance,
safety concerns, if any, associated with its use. It is the
dielectric losses, mechanical strength, appearance, and dimen-
responsibility of the user of this standard to establish appro-
sions. The effect upon these properties of change in moisture
priate safety and health practices and determine the applica-
content due to water absorption depends largely on the type of
bility of regulatory limitations prior to use.
exposure (by immersion in water or by exposure to high
humidity), shape of the part, and inherent properties of the
NOTE 1—This standard is equivalent to ISO62.
plastic. With nonhomogeneous materials, such as laminated
forms, the rate of water absorption may be widely different
2. Referenced Documents
through each edge and surface. Even for otherwise homoge-
2.1 ISO Standard:
neous materials, it may be slightly greater through cut edges
ISO62Plastics—Determination of Water Absorption
than through molded surfaces. Consequently, attempts to
correlatewaterabsorptionwiththesurfaceareamustgenerally
3. Significance and Use
be limited to closely related materials and to similarly shaped
specimens: For materials of widely varying density, relation
3.1 This test method for rate of water absorption has two
between water-absorption values on a volume as well as a
chief functions: first, as a guide to the proportion of water
weight basis may need to be considered.
absorbed by a material and consequently, in those cases where
therelationshipsbetweenmoistureandelectricalormechanical
4. Apparatus
properties, dimensions, or appearance have been determined,
4.1 Balance—An analytical balance capable of reading
as a guide to the effects of exposure to water or humid
0.0001 g.
conditions on such properties; and second, as a control test on
the uniformity of a product. This second function is particu-
4.2 Oven, capable of maintaining uniform temperatures of
50 63°C (122 65.4°F) and of 105 to 110°C (221 to 230°F).
ThistestmethodisunderthejurisdictionofASTMCommitteeD20onPlastics
and is the direct responsibility of Subcommittee D20.50 on Durability of Plastics. Additional information regarding diffusion of liquids in polymers can be found
Current edition approved April 1, 2010. Published June 2010. Originally in the following references: (1) Diffusion, Mass Transfer in Fluid Systems, E.L.
approved in 1940. Last previous edition approved in 2005 as D570-98 (2005). Cussler, Cambridge University Press, 1985, ISBN 0-521-29846-6, (2) Diffusion in
DOI: 10.1520/D0570-98R10E01. Polymers, J. Crank and G.S. Park, Academic Press, 1968, and (3) “Permeation,
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St., Diffusion, and Sorption of Gases and Vapors,” R.M. Felder and G.S. Huvard, in
4th Floor, New York, NY 10036, http://www.ansi.org. Methods of Experimental Physics, Vol 16C, 1980, Academic Press.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D570 − 98 (2010)
TABLE 1 Time to Saturation for Various Thickness of Nylon-6
Type of Dimensions to Be Measured to
Specimen the
Typical Time to 95 %
Thickness, mm
Nearest 0.025 mm (0.001 in.)
Saturation, h
Molded disk thickness
1 100
Sheet thickness
2 400
Rod length and diameter
3.2 1 000
Tube inside and outside diameter, and
10 10 000
wall thickness
25 62 000
6. Conditioning
6.1 Three specimens shall be conditioned as follows:
6.1.1 Specimens of materials whose water-absorption value
would be appreciably affected by temperatures in the neigh-
5. Test Specimen
borhood of 110°C (230°F), shall be dried in an oven for 24 h
at 50 63°C (122 65.4°F), cooled in a desiccator, and imme-
5.1 The test specimen for molded plastics shall be in the
diately weighed to the nearest 0.001 g.
form of a disk 50.8 mm (2 in.) in diameter and 3.2 mm ( ⁄8 in.)
inthickness.Permissiblevariationsinthicknessare 60.18mm
NOTE 3—If a static charge interferes with the weighing, lightly rub the
(60.007 in.) for hot-molded and 60.30 mm (60.012 in.) for
surface of the specimens with a grounded conductor.
cold-molded or cast materials.
6.1.2 Specimens of materials, such as phenolic laminated
plastics and other products whose water-absorption value has
5.2 ISO Standard Specimen—The test specimen for homo-
been shown not to be appreciably affected by temperatures up
geneous plastics shall be 60 by 60 by 1 mm. Tolerance for the
to 110°C (230°F), shall be dried in an oven for1hat105to
60-mm dimension is 62mmand 60.05 mm for the 1-mm
110°C (221 to 230°F).
thickness.This test method and ISO62 are technically equiva-
6.1.3 When data for comparison with absorption values for
lent when the test specimen described in 5.2 is used.
other plastics are desired, the specimens shall be dried in an
5.3 Thetestspecimenforsheetsshallbeintheformofabar
oven for 24 h at 50 63°C (122 65.4°F), cooled in a desic-
76.2 mm (3 in.) long by 25.4 mm (1 in.) wide by the thickness
cator, and immediately weighed to the nearest 0.001 g.
of the material. When comparison of absorption values with
7. Procedure
molded plastics is desired, specimens 3.2-mm ( ⁄8-in.) thick
should be used. Permissible variations in thickness shall be
7.1 Twenty-Four Hour Immersion—The conditioned speci-
0.20 mm (60.008 in.) except for materials which have greater
mens shall be placed in a container of distilled water main-
standard commercial tolerances.
tained at a temperature of 23 61°C (73.4 61.8°F), and shall
rest on edge and be entirely immersed. At the end of 24, + ⁄2,
5.4 Thetestspecimenforrodsshallbe25.4-mm(1-in.)long
−0 h, the specimens shall be removed from the water one at a
for rods 25.4 mm in diameter or under and 12.7-mm ( ⁄2-in.)
time, all surface water wiped off with a dry cloth, and weighed
long for larger-diameter rods. The diameter of the specimen
tothenearest0.001gimmediately.Ifthespecimenis ⁄16in.or
shall be the diameter of the finished rod.
less in thickness, it shall be put in a weighing bottle immedi-
5.5 The test specimen for tubes less than 76 mm (3 in.) in ately after wiping and weighed in the bottle.
inside diameter shall be the full section of the tube and
7.2 Two-Hour Immersion—For all thicknesses of materials
25.4-mm(1-in.)long.Fortubes76mm(3in.)ormoreininside
having a relatively high rate of absorption, and for thin
diameter, a rectangular specimen shall be cut 76 mm in length
specimens of other materials which may show a significant
in the circumferential direction of the tube and 25.4 mm in
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