IEC 62788-6-2:2020提供了测量聚合物材料（如密封剂、边缘密封件、前片和后片）的稳态水蒸气透过率（WVTR）、水蒸气渗透性（P）、扩散率（D）、溶解度（S）和水分穿透时间（？10）（定义为达到稳态WVTR 10%的时间）的方法。这些测量可在选定的温度和湿度水平下进行，以评估其在光伏组件中的性能。测量是通过检查瞬态WVTR曲线并将其拟合到理论Fickian模型来完成的。 本文件最适用于单片薄膜。如果使用多层膜，D和S值仅为表观值，但稳态值仍可测量。

IEC 62788-6-2:2020 provides methods for measuring the steady-state water vapour transmission rate (WVTR), water vapour permeability (P), diffusivity (D), solubility (S), and moisture breakthrough time (？10) (defined as the time to reach 10 % of the steady state WVTR) for polymeric materials such as encapsulants, edge seals, frontsheets and backsheets. These measurements can be made at selected temperatures and humidity levels as deemed appropriate for evaluation of their performance in PV modules. Measurement is accomplished by inspection of the transient WVTR curve and by fitting it to a theoretical Fickian model. This document is best applied to monolithic films. If multilayer films are used, the D and S values are only apparent values, but the steady-state values can still be measured.