Information on the most widely used ASTM standards within the materials testing industry
ASTM D570: Standard Test Method for Water Absorption of Plastics
ASTM D570 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.
Note 1: This test method and ISO 62 are technically equivalent when the test specimen described in 6.2 is used.
This test method for rate of water absorption has two chief functions:
1, 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;
2, 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.
Some common plastic material water absorption data:

Related Standard
ISO 62 Moisture content test, Plastics — Determination of water absorption
ISO 62:2008 describes a procedure for determining the moisture absorption properties in the“through-the-thickness”direction of flat or curved-form solid plastics. It also describes procedures for determining the amount of water absorbed by plastic specimens of defined dimensions, when immersed in water or when subjected to humid air under controlled conditions.
The“through-the-thickness” moisture diffusion coefficient can be determined for single-phase material by assuming Fickian diffusion behaviour with constant moisture absorption properties through the thickness of the test specimen. This model is valid for homogeneous materials and for reinforced polymer-matrix composites tested below their glass transition temperature. However, some two-phase matrices such as hardened epoxies may require a multi-phase absorption model which is not covered by this International Standard.
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