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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Then the permeance is calculated by dividing the WVT by the vapor pressure across the material under test. Verify that the units are the same Method: We use cookies to understand how you use our site and to improve your experience. Water in the gas asym is invisible.

The Significance of the Permeability of Paints

They run essentially the same kinds of tests as in the ASTM methods, but do so instrumentally. This correction can greatly change the results. The method that most closely approaches the conditions of use should be selected.

If the container is filled with desiccant, the method is called the dry cup method or the desiccant method. The WVT is determined by dividing the rate of weight change, which is the slope of the plot, by the area of the test specimen.

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The Significance of the Permeability of Paints | KTA UniversityKTA University

It can be used to test paper, plastic films, other sheet materials, fiberboards, gypsum and plaster products, wood products, and plastics. It can also be produced by the boiling of water, but the wstm that you can see coming out of your kettle technically is not water vapor. What is water vapor? ASTM D does not discuss this correction.

If a sample is tested twice by the dry cup method, and each test consists of three replicate trials, asfm difference between the permeance results from the two tests are expected to be less than a quarter of a perm if the d153 is less than 1 perm.

Temperature and Relative Humidity Testing Standard: All paint and coatings are permeable to water, just to different degrees. What should one consider when comparing the permeance of coatings?

These values are for use in design, manufacture, and marketing.

If the cup is filled with water, the dish loses water over the course of the test so the plot points downward. The permeability is calculated by multiplying the permeance by the thickness of the material. The scopes of the standards differ considerably.

The steam that you see consists of very small droplets of liquid water suspended in air. Leave this field empty. WVT is determined by sealing a free film of the test material to the top of a container that is filled with water left or desiccant right.


For the wet cup method, two results, each the mean of triplicate trials, are expected to differ by less than These three terms are used to describe how quickly water vapor diffuses through a solid material.

This includes personalizing content and advertising. ASTM E96 covers many materials, including coatings.

What does the magnitude of the permeance indicate? Hence, the water vapor transmission characteristics of asm are important in assessing their performance in practical use. The films may be free films or they may be applied to porous substrates. 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 fundamentals of the measurement of water vapor transmission in the laboratory are simple. However, it appears that no side-by-side tests have been run comparing results from measurements with such instruments to these ASTM methods for precision and accuracy. How precise is the testing?