ISO 62:2008描述了一种测定扁平或弯曲形状固体塑料在“整个厚度”方向上吸湿性能的程序。它还描述了当浸入水中或在受控条件下暴露在潮湿空气中时，确定规定尺寸塑料试样吸收水量的程序。单相材料的“贯穿厚度”水分扩散系数可以通过假设菲茨基扩散行为来确定，该行为具有贯穿试样厚度的恒定吸湿性。 该模型适用于均质材料和在玻璃化转变温度以下测试的增强聚合物基复合材料。然而，一些两相基质，如硬化环氧树脂，可能需要本国际标准未涵盖的多相吸收模型。 使用本国际标准中所述方法获得的结果适用于大多数塑料，但不适用于多孔塑料、颗粒或粉末，因为它们可能表现出额外的吸收和毛细管效应。 塑料在受控条件下暴露在规定的时间段内，可提供它们之间的相对比较。

ISO 62:2008 describes a procedure for determining the moisture absorption properties in the “through-the-thickness” direction of flat or curved-form solid plastics. It also describes procedures for determining the amount of water absorbed by plastic specimens of defined dimensions, when immersed in water or when subjected to humid air under controlled conditions. The “through-the-thickness” moisture diffusion coefficient can be determined for single-phase material by assuming Fickian diffusion behaviour with constant moisture absorption properties through the thickness of the test specimen. This model is valid for homogeneous materials and for reinforced polymer-matrix composites tested below their glass transition temperature. However, some two-phase matrices such as hardened epoxies may require a multi-phase absorption model which is not covered by this International Standard. The results obtained using the methods described in this International Standard are applicable to most plastics but are not applicable to cellular plastics, granulates or powders, which can show additional absorption and capillary effects. Plastics exposed to moisture under controlled conditions for defined periods of time provide relative comparisons between them.