Information on the most widely used ASTM standards within the materials testing industry
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. It is crucial for evaluating how plastics behave in humid or wet environments, as water absorption can significantly affect dimensional stability, mechanical properties, electrical insulation, and long-term performance.
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 Interational Standard.
Test Principle:
The core principle is gravimetric analysis. The mass of a dried specimen is measured, then the specimen is exposed to water or a humid environment under controlled conditions (temperature, time). After exposure, the specimen is removed, surface water is wiped off, and it is weighed again. The water absorption is calculated as the increase in mass, expressed as a percentage of the original dry mass.

Specific Test Methods
The standard outlines three principal methods:
Method 1: Immersion in water at 23°C. This is the most common method, providing a baseline for comparison.
Method 2: Immersion in boiling water. An accelerated test to assess resistance to severe conditions.
Method 3: Conditioning in humid atmosphere (50% relative humidity). Simulates long-term exposure to a humid environment.
Test Specimen:
Shape & Dimensions: Typically discs (50 mm diameter) or square plates (50 mm x 50 mm) with a thickness as specified by the relevant material standard (often 1 mm or 3 mm).
Conditioning: Specimens must be dried to constant mass in an oven (e.g., 24 hours at 50°C ± 2°C) or a desiccator before testing.
Quantity: A minimum of three specimens is required for statistical relevance.
General Test Procedures:
Dry specimens to constant mass (m₁).
Immerse or condition specimens according to the chosen method (e.g., 24 hours or longer in 23°C water).
Remove specimens, quickly wipe off surface water with a dry cloth, and weigh immediately (m₂).
Calculate water absorption: [(m₂ - m₁) / m₁] x 100%.
Report the mean value and standard deviation.
Related products and device
Related Standard
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.
Require More Customized Solutions?