用拟二元方法研究iPP-DBP-DOP三元体系的热致相分离热力学

采用拟二元方法研究等规聚丙烯（iPP）‐邻苯二甲酸二丁酯（DBP）‐邻苯二甲酸二辛酯（DOP）三元聚合物溶液的热致相分离热力学，得出了拟二元相图的数学关联方法.采用光学显微镜法测定浊点温度， 采用差式扫描量热法（DSC）测定熔点、动态结晶温度.利用浊点测定数据回归聚合物-共溶剂的交互作用参数 χ的表达式，χ是共溶剂配比和温度的函数，以此为基础计算的拟二元相图与实验数据吻合较好.发现共溶剂中DBP份数增加，相分离类型由单纯固液分相形式转变为液液分相、固液分相依次发生形式，共溶剂配比能调控拟二元相图结构.研究表明，只需测定一个较低冷却速率下几种共溶剂配比的拟二元溶液的浊点温度、分别测定几个冷却速率下iPP–DOP二元溶液的动态结晶温度即可掌握该三元溶液热致相分离热力学的全部信息.其可用来指导制膜过程，并能准确预测形成的膜结构形貌.

Thermodynamics of thermally induced phase separation of iPP-DBP-DOP ternary solution by pseudo-binary approach

The thermally induced phase separation thermodynamics of the ternary solution consisting of isotactic polypropylene (iPP), di-n-butyl phthalate (DBP) and dioctyl phthalate (DOP) was studied by pseudo-binary approach,considering the co-solvents of DBP and DOP as one component.The mathematical model to calculate pseudo-binary temperature-concentration phase diagrams was proposed. The cloud point curves of iPP-co-solvents systems were obtained with optical microscopy at a cooling rate of 1K•min^-1.The melting point curves and dynamic crystallization lines of iPP-co-solvents systems were determined with differential scanning calorimetry(DSC) at several cooling rates.The interaction parameter χ between iPP and co-solvents was a function of temperature and co-solvents composition，and was determined from cloud point curves of iPP-co-solvents systems.Good agreement was obtained between the pseudo-binary phase diagrams calculated from the mathematical model and the ones generated from experiments. With increasing DBP fraction in co-solvents, the phase separation of the ternary solution changed from solid-liquid to liquid-liquid with subsequent solid-liquid.By varying the co-solvents composition systematically, the pseudo-binary phase diagrams could be controlled successfully.The thermodynamics of thermally induced phase separation of iPP-DBP-DOP ternary solution could be obtained by only measuring the cloud point curves of pseudo-binary systems of several co-solvents compositions at a lower cooling rate and dynamic crystallization lines of iPP-DOP system at several cooling rates.In the end, it was illustrated that the resulting membrane morphology could be explained successfully with the thermodynamics of iPP-DBP-DOP solution studied via the pseudo-binary approach.