Effect of temperature-dependent microstructure evolution on pore wetting in PTFE membranes under membrane distillation conditions
Effect of temperature-dependent microstructure evolution on pore wetting in PTFE membranes under membrane distillation conditions
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DOI：
10.1016/j.memsci.2012.11.049
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发表时间：
2013-02-15
影响因子：
9.5
通讯作者：
Arafat, Hassan A.
中科院分区：
文献类型：
--
作者：
Saffarini, Rasha B.;Mansoor, Bilal;Arafat, Hassan A.
在某些应用中，如膜蒸馏（MD），影响工艺性能的一个关键参数是多孔膜的入液压力（LEP）。在这项工作中，三个0.2 μ m的商业膨胀聚四氟乙烯（PTFE）膜在MD条件下的润湿行为进行了评估。研究了温度对膜的微观结构和稳定性的影响，以及温度对LEP的影响。在MD进料温度范围（25-70℃）内，所有三种膜的LEP实验结果与由公认的拉普拉斯（康托）方程获得的理论估定值存在偏差，反映了几何因子随温度的变化。热重分析（TGA）表明，在低于350℃的温度下，膜没有降解，差示扫描量热法（DSC）测量显示，在膨胀的PTFE膜的互连连续原纤维中可能存在内应力松弛。通过扫描电子显微镜在温度从25℃逐渐升高到50℃时拍摄的高分辨率二次电子图像的比较，揭示了由于所有三种膜的纤维扭曲而导致的微观结构演变的进一步证据。因此，在LEP估计的拉普拉斯（康托）公式中必须考虑温度相关的几何校正因子，以预测非等温条件下PTFE膜的润湿。结果表明，除了膜孔径和疏水性外，微观结构随温度的变化对膨胀膜的润湿性也有显著影响。(C) 2012 Elsevier B.V.版权所有
In certain applications, such as membrane distillation (MD), one key parameters affecting the process performance is liquid entry pressure (LEP) of the porous membranes. In this work, three 0.2-mu m commercial expanded polytetrafluroethylene (PTFE) membranes were evaluated for wetting behavior under MD conditions. The effect of temperature on microstructure and stability of the membranes was investigated in relation to its impact on LEP. In the MD feed temperature range of interest, 25-70 degrees C, experimental LEP results for all three membranes showed deviations from theoretically estimated values obtained by the well-established Laplace (Cantor) equation, reflecting a changing geometric factor with temperature. While thermogravimetric analysis (TGA) measurements showed that the membranes had no degradation at temperatures less than 350 degrees C, differential scanning calorimetry (DSC) measurements revealed possible relaxation of internal stresses in the interconnected continuous fibrils of the expanded PTFE membranes. Further evidence of microstructure evolution due to fibril distortions in all three membranes was revealed by comparison of high resolution, secondary electron images taken using scanning electron microscopy at progressively increasing temperatures from 25 degrees C to 50 degrees C. Additional evidence was revealed through pore size analysis. Therefore, a temperature dependent geometric correction factor must be accounted for in the Laplace (Cantor) formulation for LEP estimation to predict the wetting of PTFE membranes under non-isothermal conditions. Present results indicate that, in addition to membrane pore size and hydrophobicity, microstructure evolution with temperature significantly impacts the wettability of the expanded PTFE membranes. (C) 2012 Elsevier B.V. All rights reserved.