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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These three terms are used to describe how quickly water vapor diffuses through a solid material.

If the container is filled with desiccant, the method is called the dry cup method or the desiccant method. Water in the gas phase is invisible.

Historical Version s – view previous versions of standard. They run essentially the same kinds of tests as in the ASTM methods, but do so instrumentally. The Water Vapor Permeance is often simply call the permeance, and the water vapor permeability is often simply called the permeability.

The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. If a sample is tested twice by the dry cup 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. 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.

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. Hence, the water vapor transmission characteristics of coatings are important in assessing their performance in practical use.


ASTM D – 03 Standard Test Methods for Water Vapor Transmission of Organic Coating Films

In some services, for example, exterior wood and masonry, the coating has to allow moderate amounts of water vapor to asgm through the film without damage to it. What is water vapor? The permeance and permeability may be calculated from the WVT.

The wet cup method can produce higher results than the dry cup method when the same coating is tested under the same air temperature and humidity conditions. For example, the units might be grams per hour or nanograms per 24 hours. Leave this field aastm. Essentially, the test determines how much vapor is lost through the film in the wet cup method or how much vapor the ast attracts or draws through the film for the dry cup method.

The fundamentals of the measurement of water vapor transmission in the laboratory are simple. This includes personalizing content and advertising.

The Significance of the Permeability of Paints

First the WVT is determined. All paint asgm coatings are permeable to water, just to different degrees. 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.

If the cup is filled with water, the dish loses water over the course of the test so the plot points downward. In general, the more permeable a coating is to the passage of moisture as is typical of many water-reducible coatings, the greater its affinity for water and the greater the increase in transmission when tested in and exposed to high humidities.

Leave a Reply Cancel reply Your email address will not be published. If the container is filled with water, the method is called the wet cup method or the water method.


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

Water vapor can be produced by the evaporation of water or the sublimation of ice or snow. The scopes of the standards differ considerably. The permeability is calculated by multiplying the permeance by the thickness of the material. The repeatability values reported by these two ASTM standards indicate the permeance values determined are ball park figures.

The Water Vapor Transmission WVTpermeance, and permeability are very closely related in that one is calculated from the other. The weight data is plotted versus time. In the gas phase, water molecules move very rapidly and are not bound together. These values are for use in design, manufacture, and marketing.

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.

Materials can be classified by the magnitude of their permeance as follows. ASTM E96 covers many materials, including coatings. We use cookies to understand how you use our site and to improve your experience. 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.

Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.

Finally, be cautious when comparing the results obtained by the dry cup method to the wet cup methods. Factors for conversion are stated in What does the magnitude of the permeance indicate?