用正电子湮没寿命谱 (PALS)研究了温度和 PEG含量对以聚己二酸丁二醇酯 (PBA)为软段的聚酯聚氨酯的自由体积特性和透气性的影响 . 实验结果表明 , 自由体积空洞的体积随着温度的升高而增加 , 分布变宽 , 导致透气性增大. 不同 PEG含量的聚酯聚氨酯 PBA-10, PBA-15和 PBA-20的水汽渗透系数 (WVP)基本相同 . 结果表明 , 在这类聚氨酯中 , 影响透气性的主要因素不仅是自由体积 , 而且与材料的亲水性有关 .

Positron annihilation lifetime spectroscopy was used to study the effect of temperature and content of PEG on the free volume size, distribution and water-vapor permeability (WVP) for a series of polyester-based polyurethane films based on poly (butylene adipate) (PBA) as soft segments. The PALS results indicated that the mean volume of free-volume increased and the distribution of free-volume broadened with the temperature increased. The variation rate of free-volume hole size as a function of temperature has an abrupt increase, which is attributed to the crystalline region melting. In all membranes, water-vapor permeability coefficient increased with the increase of temperature. PBA-20 has almost the same values of WVP as PBA-10 and PBA-15. More PEG groups added exert no significant effects on the water-vapor permeability, because there are two opposite effects of PEG groups on WVP. The experimental results indicated that WVP could be controlled by not only free volume, but also hydrophilicity of polymer.