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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Factors for conversion are stated in ASTM E96 covers many materials, including coatings. Water astj is the gaseous phase of water. Water in the gas phase is invisible. How precise is the testing? First the WVT is determined. The fundamentals of the measurement of water vapor transmission in the laboratory are simple.
These values are for use in design, manufacture, and marketing. Finally, be cautious when comparing the results obtained by the dry cup method to the wet cup methods.
ASTM D – 13 Standard Test Methods for Water Vapor Transmission of Organic Coating Films
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. The films may be free films or they may be applied to porous substrates. The permeability is calculated by multiplying the permeance by the thickness of the material.
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.
In either case, the slope of the plot is the rate of weight change and its units are mass per time. In the gas phase, water molecules move very rapidly and are not bound together.
All paint and coatings are permeable to water, just to different degrees. These three terms are used to describe how quickly water vapor diffuses through a atsm material.
What does the magnitude of the permeance indicate? The films may be free films or they may be applied to porous substrates. Then the permeance is calculated by dividing the WVT by the vapor pressure across the material under test.
For example, the units might be grams per hour or nanograms per 24 hours. ASTM D covers the evaluations of films of d1635 ASTM D does not discuss this correction. What should one consider when comparing the permeance of coatings? Leave a Reply Cancel reply Your email address will not be published. Otherwise blistering and peeling will likely occur. 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.
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. Inspection Instruments Pipeline Coatings — Volume 2: The scopes of the standards differ considerably.
The Significance of the Permeability of Paints
If the container is filled with desiccant, the method is called the dry cup method or the desiccant method. 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 WVT is determined by dividing x1653 rate of weight change, which is the slope of the plot, by the area of the test specimen. 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.
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. This correction can greatly change the results. Temperature and Relative Humidity Testing Standard: It can also d163 produced by the boiling of water, but the steam that you can see coming out of your kettle technically is not water vapor.
ASTM D – 03 Standard Test Methods for Water Vapor Transmission of Organic Coating Films
Link to Active This link will always route to the current Active version of the standard. The permeance and permeability may be calculated from the WVT. The Water Vapor Transmission WVTpermeance, and permeability are very closely related in that one is calculated from the other. Essentially, the test determines how much vapor is lost through the film in the wet cup method or how much vapor the desiccant attracts or draws through the film for the dry cup method.
Materials can be classified by the magnitude of their permeance as follows.