ASTM D570-98

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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
Designation:D 570–98
Standard Test Method for
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Water Absorption of Plastics
This standard is issued under the fixed designation D 570; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2 Comparison of water absorption values of various plas-
tics can be made on the basis of values obtained in accordance
1.1 Thistestmethodcoversthedeterminationoftherelative
with 7.1 and 7.4.
rate of absorption of water by plastics when immersed. This
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3.3 Ideal diffusion of liquids into polymers is a function of
test method is intended to apply to the testing of all types of
the square root of immersion time. Time to saturation is
plastics, including cast, hot-molded, and cold-molded resinous
strongly dependent on specimen thickness. For example,Table
products, and both homogeneous and laminated plastics in rod
1 shows the time to approximate time saturation for various
and tube form and in sheets 0.13 mm (0.005 in.) or greater in
thickness of nylon-6.
thickness.
3.4 The moisture content of a plastic is very intimately
1.2 The values given in SI units are to be regarded as the
related to such properties as electrical insulation resistance,
standard. The values stated in parentheses are for information
dielectric losses, mechanical strength, appearance, and dimen-
only.
sions. The effect upon these properties of change in moisture
1.3 This standard does not purport to address all of the
content due to water absorption depends largely on the type of
safety concerns, if any, associated with its use. It is the
exposure (by immersion in water or by exposure to high
responsibility of the user of this standard to establish appro-
humidity), shape of the part, and inherent properties of the
priate safety and health practices and determine the applica-
plastic. With nonhomogeneous materials, such as laminated
bility of regulatory limitations prior to use.
forms, the rate of water absorption may be widely different
NOTE 1—ISO62 is technically equivalent to this test method.
through each edge and surface. Even for otherwise homoge-
neous materials, it may be slightly greater through cut edges
2. Referenced Documents
than through molded surfaces. Consequently, attempts to
2.1 ASTM Standards:
correlatewaterabsorptionwiththesurfaceareamustgenerally
D647 Practice for Design of Molds for Test Specimens of
be limited to closely related materials and to similarly shaped
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Plastic Molding Materials
specimens: For materials of widely varying density, relation
2.2 ISO Standard:
between water-absorption values on a volume as well as a
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ISO 62 Plastics—Determination of Water Absorption
weight basis may need to be considered.
3. Significance and Use
4. Apparatus
3.1 This test method for rate of water absorption has two
4.1 Balance—An analytical balance capable of reading
chief functions: first, as a guide to the proportion of water
0.0001 g.
absorbed by a material and consequently, in those cases where
4.2 Oven, capable of maintaining uniform temperatures of
therelationshipsbetweenmoistureandelectricalormechanical
50 63°C (122 65.4°F) and of 105 to 110°C (221 to 230°F).
properties, dimensions, or appearance have been determined,
as a guide to the effects of exposure to water or humid
5. Test Specimen
conditions on such properties; and second, as a control test on
5.1 The test specimen for molded plastics shall be in the
the uniformity of a product. This second function is particu-
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form of a disk 50.8 mm (2 in.) in diameter and 3.2 mm ( ⁄8 in.)
larly applicable to sheet, rod, and tube arms when the test is
in thickness (see Note 2). Permissible variations in thickness
made on the finished product.
are 60.18 mm (60.007 in.) for hot-molded and 60.30 mm
(60.012 in.) for cold-molded or cast materials.
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ThistestmethodisunderthejurisdictionofASTMCommitteeD-20onPlastics
andisthedirectresponsibilityofSubcommitteeD20.50onPermanenceProperties.
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Current edition approved July 10, 1998. Published January 1999. Originally Additional information regarding diffusion of liquids in polymers can be found
published as D570–40T. Last previous edition D570–95. in the following references: (1) Diffusion, Mass Transfer in Fluid Systems, E.L.
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Discontinued1994;replacedbyD1896,D3419,D3641,D4703,andD5227. Cussler, Cambridge University Press, 1985, ISBN 0-521-29846-6, (2) Diffusion in
See 1994 Annual Book of ASTM Standards, Vol 08.01. Polymers, J. Crank and G.S. Park, Academic Press, 1968, and (3) “Permeation,
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Available from American National Standards Institute, 11 W. 42nd St., 13th Diffusion, and Sorption of Gases and Vapors,” R.M. Felder and G.S. Huvar
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