ASTM E96/E96M-05 pdf free download.Standard Test Methods for Water Vapor Transmission of Materials.
1.1 These test niethixis 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 11/4 in. (32 mm) in thickness except as provided in Section 9. Two basic methods, the Desiccant Method and the Water Method, are provided thr the measurement of permeance, and two variations 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 different methods. The method should be selected that more nearly approaches the conditions of use.
1.2 The values stated in inch-pound units are to he regarded separately as the standard. Within the text, the SI units are shown in parentheses. The values stated in each system are not exact equivalents: therefore each system must be used mdcpendently of the other. Combining values from two systems will result in non-conformance with the standard. However derived results can be convened from one system to other using appropriate conversion factors (see Table 1).
3. Terminology
3. 1 Definitions of terms used in this standard will be found in Terminology C168. from which the following is quoted:
“water vapor permeabtility—the time rate of water vapor transmission through unit area of flat material of unit thickness induced by unit var pressure difference between two specific surfaces, under specilied temperature and humidity conditions.
3. I . I Discussion—Permeability is a property of a material, hut the permeability of a body that pertorms like a material may be used. Permeability is the arithmetic product of permeance and thickness.
water rapor permeaiice—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 specilIed ternperawre and humidity conditions.
3. 1 .2 DLscus.sion—Permeance is a performance evaluation and not a property of a material.
3.2 water vapor traiismission rate—the steady water vapor flow in unit time through unit area of a body, normal to specific parallel surfaces, under specilic conditions of temperature and humidity at each surface.”ASTM E96/E96M pdf download.