ASTM E398 Standard Test Method for Water Vapor Transmission Rate of Sheet Materials

The standard "ASTM E398 Standard Test Method for Water Vapor Transmission Rate of Sheet Materials Using Dynamic Relative Humidity Measurement," developed by the American Society for Testing and Materials (ASTM), describes a test method for the dynamic evaluation of water vapor transfer rate through a flexible barrier material. This standard also allows conversion to generally accepted water vapor transmission units obtained by other test methods, including the gravimetric method described in ASTM E96/E96M.

This test method is limited to flexible barrier sheet materials composed entirely of hydrophobic materials or combinations of hydrophobic and hydrophilic materials with at least one surface hydrophobic.

The minimum test value obtained with this test method is limited by the infiltration of water vapor through the compression seals of the test device. Any test result, including the desiccant procedure of ASTM E96/E96M, at 37,8 degrees Celsius and 90 percent relative humidity water vapor transmission A reasonable value for the method is about 0,01 g/24 h m² This limit can be checked for each instrument with an impermeable sample, such as aluminum foil. Calibration procedures can compensate for the leak rate, if specified.

This test method is currently not suitable for referee testing, but is suitable for control testing and material comparison.

Several other ASTM test methods exist for testing a similar property. This test method is unique in that it closely replicates typical product storage where moisture transfer from a package to the environment is allowed to proceed without continuously sweeping the environmental side with dry gas. Among the methods that continuously sweep the dry sides ASTM: There are test methods in F1249, ASTM F372 and ASTM F1770 standards.

No single set of test conditions can represent all climatic and usage conditions, so this water vapor transmission rate test method serves to compare different materials within a specified set of conditions rather than to predict their actual performance in the field under any given condition. Under known and carefully controlled conditions, the water vapor transmission rate can be used to evaluate a board's vapor barrier properties. Direct correlation of values ​​obtained under different conditions, such as test temperature and relative humidity, is valid provided that the barrier material under test does not undergo changes in solid state (such as crystalline transition or melting point) during or between test conditions.

The Standard Test Method for Water Vapor Transmission Rate of Sheet Materials Using Dynamic Relative Humidity Measurement is a method used to determine the rate at which water vapor passes through sheet materials such as films, coatings, or membranes. This is critical for evaluating materials used in packaging, construction, textiles, and other applications where moisture control is important.

This method typically includes:

• Enclosing a sample sheet of material between two controlled environments.
• Exposing one side of the material to a high relative humidity and the other side to a lower relative humidity.
• Measuring the amount of water vapor that penetrates a material over time.
• Usually g/m²Calculation of water vapor transmission rate expressed as water vapor per day.

Dynamic relative humidity methods include:

• Constantly or periodically changing relative humidity conditions.
• Using sensors to measure changes in relative humidity on the dry side of the sample in real time.
• Allowing for faster and potentially more accurate measurements.

In short, ASTM E398 standard includes a procedure for dynamically evaluating the rate of water vapor transmission through flexible barrier materials. This method is particularly useful for evaluating materials used in packaging, construction, textiles, and other applications where moisture control is critical.

The main areas of application of this standard are:

• Packaging industry: Evaluation of moisture barrier properties of packaging materials to ensure product stability.
• Building materials: Evaluating materials used in building envelopes to control indoor humidity levels.
• Textiles: Determination of breathability and moisture control properties of fabrics.
• Electronics: Providing protective barriers against moisture for sensitive electronic components.

The test method described in the ASTM E398 standard is considered important for the following reasons:

• Realistic humidity control testing: Many products are exposed to changing humidity conditions, not static ones. This standard uses dynamic relative humidity measurement, which more accurately replicates actual storage or usage conditions than static tests. This helps ensure that materials perform as expected in the real world, whether for packaging, construction, or consumer goods.
• Critical to packaging performance: In food, pharmaceutical, and medical packaging, even small amounts of moisture ingress can spoil or degrade products. This standard helps manufacturers select and verify barrier materials that meet stringent moisture protection requirements.
• Vital to building and construction materials: Moisture ingress into building walls and roofs can lead to mold, rot, and energy inefficiency. Testing with this standard allows engineers to evaluate barrier films and membranes under more realistic environmental conditions.
• Accuracy and precision: Provides a quantitative, repeatable, and precise method. Dynamic relative humidity testing is generally more reliable for detecting small levels of moisture permeation, especially for high-performance barrier materials.
• Regulatory compliance and material comparison: Many industries require compliance with barrier performance standards. This standard provides a recognized, standardized protocol for comparing materials across manufacturers or meeting specification requirements.

In short, the ASTM E398 standard is important because it gives engineers, scientists, and manufacturers a more realistic and technically sound way to test and trust the moisture barrier properties of their materials.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, boasts a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the "ASTM E398 Standard Test Method for Water Vapor Transmission Rate of Board Materials Using Dynamic Relative Humidity Measurement."