ASTM D and ASTM E96 both address the determination of the water vapor transmission and permeance of coatings. ASTM E96/E96M. ASTM D Standard Test Methods for Water Vapor Transmission of Organic Coating Films. Buy ASTM D R TEST METHODS FOR WATER VAPOR TRANSMISSION OF ORGANIC COATING FILMS from SAI Global.

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If the container is filled with desiccant, the method is called the dry cup method or the desiccant method. What is water vapor?

Materials can be classified by the magnitude of their permeance as follows. The permeability is calculated by multiplying the permeance by the thickness of the material.

The system may at first gain or lose weight more quickly, and then settle into a constant or steady-state rate of weight change after a couple of days, or longer, depending on the type of material being tested. First the WVT is determined. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

What are the formulas and units for WVT, permeance, and permeability? The method that most closely approaches the conditions of use should be selected. Inspection Instruments Zstm Coatings — Volume 2: WVT is determined by sealing a free film of the test v1653 to the top of a container that is filled with water left or desiccant right.

The films may be free films or they may be applied to porous substrates. In either case, the slope of the plot is the rate of weight change and its units are mass per time. For the wet cup method, two results, each the mean of triplicate trials, are expected to differ by less than Finally, be cautious when comparing the results obtained by the dry cup method to the wet cup methods.

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Absorption of water may make a coating less dense, thus allowing moisture to diffuse easily and cause a much higher moisture vapor transmission rate, WVTR than would occur in drier environments.

The Significance of the Permeability of Paints

If the cup contains desiccant, the dish gains water weight over the course of the test, so the plot points upward. What should one consider when comparing the permeance of coatings? In the gas phase, water molecules move very rapidly and are not bound together. Then the permeance is calculated by dividing the WVT by the vapor pressure across the material under test. The Water Vapor Permeance is often simply call the permeance, and the water vapor permeability is often simply called the permeability.

ASTM D covers the evaluations of films of coatings: This correction can greatly change the results.

ASTM D – 13 Standard Test Methods for Water Vapor Transmission of Organic Coating Films

By continuing to use our site, you accept our use of cookies To learn more, click Read More to view our Privacy and Cookies Policy. These three terms are used to describe how quickly water vapor diffuses through a solid material. The scopes of the standards differ considerably. They run essentially the same kinds of tests as in the ASTM methods, but do so instrumentally.

Water vapor is the gaseous phase of water. If a sample is tested twice by the dry d16653 method, and each test consists of three replicate trials, the difference between the permeance results from the two tests are expected to be less than a quarter of a perm if the permeance is less than 1 perm. Water in the gas phase is invisible. ASTM E96 covers many materials, including coatings.


If the container is filled with water, the method is called the wet cup method or the water method. Your email address will ashm be published.

The fundamentals of the measurement of water vapor transmission in the ast are simple. Verify that the units are the same Method: Leave a Reply Cancel reply Your email address will not be published. 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. Otherwise blistering and peeling will likely occur.

Temperature and Relative Humidity Testing Standard: Water vapor can be produced by the evaporation of water or the sublimation of ice or snow. Factors for conversion are stated in We use cookies to understand how you use our site and to improve your experience. See the slide below for more information about the correction. However, it appears that no side-by-side tests have been run comparing results d6153 measurements with such instruments to these ASTM methods for precision and accuracy.

How precise is the testing?