Standard Methods of Test for Water Vapor Transmission of Materials in Sheet Form
|Publication Date:||20 September 1966|
|ICS Code (Other methods of testing of metals):||77.040.99|
These methods cover determination of the rate of water vapor transmission (WVT) of materials in sheet form. The methods are applicable to materials such as paper, plastic films, and sheet materials in general. The methods are most suitable for specimens 1/8 in. (3.18 mm) or less in thickness, but may be used with caution for somewhat thicker specimens. For specimens of materials used in building construction and similar materials greater than 1/8 in. in thickness, see ASTM Methods C355, Test for Water Vapor Transmission of Thick Materials.2 Six procedures are provided for the measurement of transmission under different test conditions, as follows:
Procedure A-For use when the materials to be tested are employed in the low range of humidities.
Procedure B-For use when the materials to be tested are employed in the high range of humidities, but will not normally be wetted.
Procedure B W-For use when materials to be tested may in service be wetted on one surface but under conditions where the hydraulic head is relatively unimportant and moisture transfer is governed by capillary and water vapor diffusion forces.
Procedure C-Conducted at an elevated temperature for use with materials employed in the low range of humidities, and intended to shorten the time of testing of highly impermeable materials. This procedure eliminates, in most cases, the need for refrigeration.
Procedure D-Conducted at an elevated temperature for use with materials employed in the high range of humidities, but not normally wetted, and intended to shorten the time of testing of highly impermeable materials employed in this range. This procedure also eliminates, in most cases, the need for refrigeration.
Procedure E-For use in measuring the WVT at an elevated temperature, with a very low humidity on one side of the sheet and a high humidity on the other side.
NOTE 1-The values stated in U.S. customary units are to be regarded as the standard. The metric equivalents of U.S. customary units may be approximate.
2Annual Book of ASTM Standards, Part 18.