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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This includes personalizing content and advertising. 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.
What is water vapor? The system may at first gain or lose weight more quickly, and then settle into a constant or steady-state rate of weight change wstm a couple of days, or longer, depending on the type of material being tested.
In either case, the slope of the plot is the rate of weight change and its units are mass per time. ASTM D does not discuss this correction. 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.
See the slide below for ast information about the correction. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
The Significance of the Permeability of Paints | KTA UniversityKTA University
ASTM E96 covers many materials, including coatings. All paint and coatings are permeable to water, just to different degrees.
What are the formulas and units for WVT, permeance, and permeability? Finally, be cautious when comparing the results obtained by the dry cup method to the wet cup methods. Verify that the units are the same Method: Water vapor is the gaseous phase d653 water.
These values are for use in design, manufacture, and marketing. If the container is filled with desiccant, the method astk called the dry cup method or the desiccant method.
Hence, the water vapor transmission characteristics of coatings are important in assessing their performance in practical use.
ASTM D – 13 Standard Test Methods for Water Vapor Transmission of Organic Coating Films
The steam that you see consists of very small droplets of liquid water suspended in air. It can be used to test paper, plastic asgm, 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.
Water vapor can be produced by the evaporation aztm water or the sublimation of ice or snow. For the wet cup method, two results, each the mean of triplicate trials, are expected to differ by less than How precise is the testing?
The method that most closely approaches the conditions of use should be selected. The repeatability values reported by these two ASTM standards indicate the permeance values determined are ball park figures. What should one consider when comparing the permeance of coatings? 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. The permeability is calculated by multiplying the permeance by the thickness of the material. 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 Water Vapor Transmission WVTpermeance, and permeability are very closely related in that one is calculated from the other.
The Significance of the Permeability of Paints
The Water Vapor Permeance is often simply call the permeance, and the water vapor permeability is often simply called the permeability. WVT is f1653 by sealing a free film of the test material 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.
Inspection Instruments Pipeline Coatings — Volume 2: If the cup is filled with water, the dish loses water over the course of the test so the plot points downward. Leave this field empty. What does the magnitude of the permeance indicate? Historical Version s – view previous versions of standard. The permeance and permeability may be calculated from the WVT. The answer to the question posed is based on the substrate and the service environment.