Thermoplastic polyurethane (PU) polymers with different chemical compositions were synthesized and casted to films, and their water vapor barrier properties at different range of relative humidity (RH) were characterized. The water vapor permeability (WVP) of packaging films is one of their most important properties to identify their suitability for use as packaging materials and is rather a complicated phenomena if the polymer has polar nature. The WVPs of PU films are determined both by permeation measurements which are a steady-state method and water vapor sorption measurements which are a non-steady-state method. Effective permeability (P_eff), solubility (S_eff), and diffusion (D_eff) coefficients of PU films were determined at 23 °C within the RH range of 0–97%. It was found that P_eff, S_eff, and D_eff increased with increasing RH gradient due to water vapor and polymer interactions. Microscopic images showed that 1,4-butanediol (BDO) helped to improve porous structure. Castor oil (CO) caused a decrease in the intensity of active absorption sites, namely, the C=O···H-N hydrogen bonds between chains. Results of two methods were yielded in the same magnitude of order. In most cases, the non-steady-state (sorption) method yields higher WVP values than steady state. At 0➔85% RH, the difference was up to 8-fold. Conditioning and equilibrating of films at 50% RH helped to reach sorption data approximate to permeation data. It was suitable to use sorption measurements to estimate the WVP which is a considerable simplification for polar polymers, e.g., developed PU film.

合成了具有不同化学组成的热塑性聚氨酯（PU）聚合物，并将其流延成薄膜，并表征了它们在不同相对湿度（RH）范围内的阻水性能。包装膜的水蒸气渗透性（WVP）是其最重要的性能之一，以确定它们是否适合用作包装材料，如果聚合物具有极性，则是一种复杂的现象。PU膜的WVP可以通过稳态方法的渗透测量和非稳态方法的水蒸气吸收测量来确定。有效渗透率（P _eff），溶解度（S _eff）和扩散（D _eff）PU膜的系数是在23°C，相对湿度0-97％的范围内确定的。发现P _eff，S _eff和D _eff由于水蒸气和聚合物的相互作用，随着RH梯度的增加而增加。显微图像显示1,4-丁二醇（BDO）有助于改善多孔结构。蓖麻油（CO）引起活性吸收位点强度的降低，即链之间的C = O···HN氢键。两种方法的结果以相同的数量级产生。在大多数情况下，非稳态（吸附）方法产生的WVP值要高于稳态。在0➔85％RH下，差异最大为8倍。在50％RH下调节和平衡薄膜有助于获得接近渗透数据的吸附数据。使用吸附测量来估计WVP是合适的，这对于极性聚合物（例如显影的PU膜）而言是一个相当大的简化。