Entropic-FV活度系数模型预测膜的溶胀性能

Prediction of swelling behavior of polymeric membranes in solutions using UNIF AC-related activity coefficient model

根据Vrentas-Duda自由体积理论,结合基于UNIFAC活度系数模型,在较宽的浓度范围内预测了聚合物膜在溶液中溶胀行为。用UNIQUAC方程计算液相中组分的活度,考虑了温度对模型方程中二元交互作用参数的影响。对水/乙二醇(EG)/聚乙烯醇(PVA)膜体系,三个不同温度60℃、70℃和80℃下计算结果和实验数据基本一致。模型方程中自由体积部分影响较大,考虑聚合物的粘弹性贡献对预测结果有一定改进。

In the frame of phase equilibrium the chemical potential of component in liquid phase equals that in polymer when sorption-desorption equilibrium was reached in the solvent/polymer mixture system. Using a simple activity coefficient model in conjunction with the Vrentas-Duda free volume theory, the swelling behavior of polymeric membrane in small molecular solvents was then predicted for the system of H2O/EG/PVA over a wide range of concentrations. The activity of solvents in liquid phase was estimated by modified UNIQUAC model equations with temperature-dependent binary interaction parameters, while that in the polymeric membrane phase was predicted by Entropic-FV activity model equation being involved with free volume contribution which cannot be negligible in polymeric system. The estimations consist with experimental data at three temperatures of 60℃ , 70℃ and 80℃. It is found that the Entropic-FV model is a suitable alternative to the Flory-Huggins equation for prediction of the swelling characteristic of polymeric membranes. The estimations were improved by taking elastic effect into consideration. The research can be used for polymeric membrane material selection.