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低温热致相分离法制备PVDF-CTFE多孔膜的研究

作者：林帅，吕晓龙，张绍哲，谷杰，任凯

单位： 1，天津工业大学，省部共建分离膜与膜过程国家重点实验室，材料科学与工程学院，生物化工研究所，天津 300387；2，膜材料与膜应用国家重点实验室，天津膜天膜科技股份有限公司，，天津300457

关键词：聚偏氟乙烯-三氟氯乙烯；低温热致相分离；成膜机理；多孔膜；凝固浴温度

DOI号：

分类号： TQ028.8

出版年,卷(期):页码： 2024,44(2):55-63

摘要：

利用低温热致相分离法制备了PVDF-CTFE多孔膜，重点考察了甘油含量和凝固浴温度对成膜机理和性能的影响。结果表明，甘油有促进TIPS和NIPS的双重作用。甘油含量的提高，一方面作为非溶剂使铸膜液浊点温度与凝固浴温度的温差变大，加强了TIPS效应，使膜结构呈TIPS效应为主的双连续结构，避免了NIPS效应所致典型的指状孔结构；另一方面作为NIPS的致孔剂，会加强NIPS效应，促使发生双扩散，生成更多孔结构，二者竞争共同作用。最终甘油含量的提高使TIPS效应占主导，NIPS所致的皮层结构变薄，膜断面结构从致密堆积状向多孔蜂窝状结构转变，提高了膜的通透性。当甘油添加量为7.5%（质量分数）时，PVDF-CTFE中空纤维多孔膜综合性能最佳，拉伸断裂强度达2.6 MPa，纯水通量达86 L/(m2·h·bar)。凝固浴温度的提高，减少了铸膜液浊点温度与凝固浴的温差，减弱了TIPS效应，加强了NIPS效应的传质过程，使膜结构从蜂窝状结构向指状孔结构转变，皮层厚度增加，导致膜孔隙率和纯水通量提高，力学性能下降。当凝固浴温度为80℃时，PVDF-CTFE平板多孔膜的纯水通量为151 L/(m2·h·bar)，拉伸断裂强度为2.1 MPa。

In this paper, PVDF-CTFE porous membranes were prepared by using low temperature thermally induced phase separation (L-TIPS) method. The effects of glycerin content and coagulation bath temperature on the membrane formation mechanism and properties were investigated. The results showed that TIPS and NIPS can be promoted by adding glycerin. On the one hand, glycerin as a non-solvent, with the increase of its content, the temperature difference between cloud point temperature and coagulation bath temperature was increased. Thus the TIPS effect was strengthened, and the membrane structure presented a bicontinuous microporous structure caused by TIPS effect rather than the typical finger-like voids structure caused by NIPS effect. On the other hand, glycerin served as a pore-forming agent during the NIPS process. Therefore double diffusion process was promoted by adding glycerin and porous structure was more likely to generate with the increase of glycerin content, NIPS and TIPS effects competed against each other as the glycerin content increasing and the TIPS effect dominated in the end.Thus, thinner skin layer structure of the membrane and changes of the membrane cross-section structure from dense packing to porous honeycomb was observed.The permeability of the membrane was improve due to aforementioned structural changes. The PVDF-CTFE hollow fiber porous membrane possessed the most comprehensive properties when the content of glycerin was 7.5 %（mass fraction）, the tensile strength was 2.6 MPa, and the pure water flux reached 86 L/(m2 · h · bar). With the increase of coagulation bath temperature, the difference between cloud point temperature of casting solution and coagulation bath temperature was reduced, TIPS effect was weakened, meanwhile the mass transfer process of NIPS effect was strengthened. The membrane structure changed from honeycomb structure to finger-like voids structure, and the thickness of skin layer increased, which leads to the increase of porosity and pure water flux of membrane and the decrease of mechanical properties. When the coagulation bath temperature reached 80 ℃, the pure water flux of PVDF-CTF E flat porous membrane was 151 L/(m2 · h · bar), and the tensile strength was 2.1 MPa.

基金项目：

天津市高等学校新型膜材料及膜分离技术创新团队(TD13-5044)；山东省自然科学基金氟材料联合基金重点项目 (ZR2019LFG007)

作者简介：

林帅(1996-),男，河南邓州人，硕士生，研究方向为分离膜制备与应用

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