ASTM E96/E96M-16 pdf free download.Standard Test Methods for Water Vapor Transmission of Materials.
1.1 These test methods cover the determination of water vapor transmission (WVT) of materials through which the passage of water vapor may be of importance, such as paper. plastic films, other sheet materials, fiberboards. gypsum and plaster products, wood products, and plastics. The test methods are limited to specimens not over I ¼ in. (32 mml in thickness except as provided in Section 9. Two basic methods, the Desiccant Method and the Water Method, are provided for the measurement of pernieance, and two van ations include service conditions with one side wetted and service conditions with low humidity on one side and high humidity on the other. Agreement should not be expected between results obtained by difTerent methods. The method should be selected that more nearly approaches the conditions of use.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not he exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. However, derived results can be converted from one system to the other using appropriate conversion factors (see Table 1).
3. Terminology
3.1 Definitions of terms used in this standard will be found in Terminology C 168. from which the following is quoted:
ebwater vapor permeabilirc—the time rate of water vapor transmission through unit area of flat material of unit thickness induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions.
Discussion—Permeability is a property of a material, but the permeability of a body that performs like a material may be used. Permeability is the arithmetic product of permeance and thickness.
water vapor permeance—the time rate of water vapor transmission through unit area of flat material or construction induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions.
I)iscussion—Permeance is a performance evaluation and not a property ot a material.
3.2 water vapor Iransmission rate—the steady water vapor flow in unit time through unit area of a body, normal to specific parallel surfaces, under specific conditions of temperature and humidity at each surface.”
4. Summary of Test Methods
4.1 In the Desiccant Method the test specimen is sealed to the open mouth of a test dish containing a desiccant, and the assembly placed in a controlled atmosphere. Periodic weighings determine the rate of water vapor movement through the specimen into the desiccant.ASTM E96/E96M pdf download.