A novel instrument for the direct measurement of moisture permeation

Water transfer flux in polymer films through the process of permeation has been characterized by a new robust method that employs a first-principles, water-specific sensor to obtain highly accurate direct transient flux measurements. This method has been applied to a common polymer (Mylar® MO film), which demonstrates remarkable stability and fast equilibration in conditions of both liquid water and saturated vapor on the “wet” side of the polymer. Moisture passing through the polymer is entrained in a high velocity dry sweep gas for detection with a high precision chilled mirror hygrometer. Using the Mylar/water system as a basis, the robustness and versatility of the test method are demonstrated.