Scope:

A water vapor transmission rate (WVTR), also known as moisture vapor transmission rate (MVTR), by ASTM F1249 test  method to measure the passage of water through a material. This analysis tool using ASTM F1249 helps to calculate or measure the permeability of vapor barriers. In packaging or other industrial applications, finding the rate of vapor transmission through flexible materials is very important. The main important factors involved in the material permeation are the thickness of the material and environmental factors like temperature, relative humidity. Reliable values for the WVTR of plastic film and sheeting are determined through this test. 

Test Procedure:

For the ASTM F1249 test method distilled water is filled in a cup, and a small gap of air space is maintained between the specimen and water. The cup is then sealed, except for the test sample, to avoid vapor loss. The apparatus is weighed at first, and then at regular intervals before the effects become linear. To ensure that all weight loss is due to water vapor transfer through the specimen, the experiment must be carefully monitored. 

Video 01: Water Vapor Transmission Rate (WVTR) testing method