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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Otherwise blistering and peeling will likely occur.
What does the magnitude of the permeance indicate?
ASTM E96 covers many materials, including coatings. The films may be free films or they may be applied to porous substrates.
What should one consider when comparing the permeance of coatings? Your email address will not be published. It can be used to test paper, plastic films, other sheet materials, fiberboards, gypsum and plaster products, wood products, and plastics. The fundamentals of the measurement of water vapor transmission in the laboratory are simple. These three terms are used to describe how quickly water vapor diffuses through a solid material. Hence, the water vapor transmission characteristics of coatings are important in assessing their performance in practical use.
Essentially, the d16533 determines how much vapor is lost through the film in the wet f1653 method or how much vapor the desiccant attracts astmm draws through the film for the dry cup method. The Water Vapor Transmission WVTpermeance, and permeability are very closely related in that one is calculated from the other. Absorption of water may make a coating less dense, thus allowing moisture to diffuse easily and cause a much higher moisture vapor transmission d165, WVTR than would occur in drier environments.
For example, the units might be grams per hour or nanograms per 24 hours.
The Significance of the Permeability of Paints
These values are for use in design, manufacture, and c1653. Historical Version s – view previous versions of standard. How precise is the testing? The films may be free films or they may be applied to porous substrates.
The Significance of the Permeability of Paints | KTA UniversityKTA University
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.
If a sample is asstm twice astj 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.
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Finally, be cautious when comparing the results obtained by the dry cup method to the wet cup methods. ASTM D covers the evaluations of films of coatings: The weight data is plotted versus time. In the gas phase, water molecules move very rapidly and are not bound together. The method that most closely approaches the conditions of use should be selected. Water vapor can be produced by the evaporation of water or the sublimation of ice or snow.
In either case, the slope of the plot is the rate of weight change and its units are mass per time. What are the formulas and units for WVT, permeance, and permeability? 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.
This correction can greatly change the results.