热致相分离法制备聚偏氟乙烯微孔膜

对聚偏氟乙烯(PVDF)/碳酸二苯酯(DPC)体系,采用热致相分离(TIPS)法制备了PVDF微孔膜.通过稀释剂的溶度参数对体系的相容性进行分析,热力学相图和不同PVDF质量浓度下制备的微孔膜断面照片均证明该体系具有较宽的液-液相分离区.PVDF/DPC体系偏晶点对应的PVDF浓度约为质量分数56%,低于此浓度体系降温后先发生液-液相分离,随着PVDF浓度的增大,微孔膜断面结构由双连续结构转变为蜂窝状结构,且膜孔孔径减小,高于此浓度体系降温后只发生固-液相分离,微孔膜断面呈块状紧密堆积结构.较快的冷却速率有利于低PVDF浓度时较小孔径膜和高PVDF浓度时较小球粒尺寸膜的生成.

Preparation of polyvinylidene fluoride membranes via thermally induced phase separation method

Polyvinylidene fluoride (PVDF) microporous membranes were prepared via thermally induced phase separation (TIPS) method of PVDF blended with diphenyl carbonate (DPC). The compatibility between PVDF and diluent was analyzed in the view of solubility parameter. A larger liquid - liquid phase separation region was obtained from PVDF/DPC system, which was confirmed by the thermodynamic phase separation of PVDF/DPC system and the SEM photographs of cross - section of PVDF membranes at different polymer mass fractions.The polymer mass fraction on the monotectic point of PVDF/DPC system was 56%. When quenching the PVDF/DPC solution with a polymer mass fraction lower than that in ice water, the liquid - liquid phase separa-tion occurred prior to polymer crystallization. With the increase of polymer mass fraction, the morphology of the resulting membrane changed from a typical bicontinuous structure to a celluar structure, and the pore size of membranes decreased. However, only the polymer crystallization occurred if further increasing the polymer mass fraction, which resulted in the block close packing structure. In addition, the faster cooling rate resulted in smaller pore sizes at polymer concentration of 30% and smaller spherulite particles at polymer concentration of 70%.