添加剂对双凝固浴法PVDF膜结构及性能的影响

Effect of additives on morphology and performance of PVDF membranes via dual-bath coagulation

以N,N二甲基乙酰胺(DMAc)为溶剂,以聚乙二醇(PEG-400)、正硅酸乙酯(TEOS)为添加剂,采用双凝固浴法制备PVDF多孔膜。考察了聚乙二醇(PEG)、正硅酸乙酯(TEOS)单独及二者复配使用时,添加剂含量或配比对PVDF膜结构及性能的影响。结果表明,PEG-400的主要致孔位置为膜表面,而TEOS的主要致孔位置为膜断面;PEG含量增加,膜表面孔径增大,膜的气通量增大,表面疏水性降低;TEOS含量增加,膜内球晶数量增多,机械强度下降,膜的气通量增大,表面疏水性提高。采用PEG-TEOS复合添加剂,可以起到优化膜性能的效果,实验范围内,当添加剂质量含量为10%,m(PEG)/m(TEOS)=6∶4时,膜的综合性能最好。

Hydrophobic polyvinylidene fluoride( PVDF) membrane were fabricated by a dual-bath coagulation bath method. The first coagulant was isopropanol and the second coagulant was water. N,N-dimethylacetamide( DMAc) was used as solvent. Polyethylene glycol( PEG-400) and tetraethylorthosilicate( TEOS) were used as additives. Effect of the additive content or mass ratio of PEG-400 to TEOS on membrane morphology and performances such as wettability,permeability and mechanical property were investigated. The SEM images of the membranes revealed that the pore-forming region of PEG-400 was top surface,and the pore-forming region of TEOS was the cross section. As the content of PEG-400 increased,the number of top surface pores and pore size increased and the nitrogen flux increased,too. But the hydrophobic of the top surface decreased with increasing the content of PEG. As the content of TEOS increased,the number of crystalline particles and the nitrogen flux increased,at the same time,the hydrophobic of the top surface increased and the mechanical strength decreased. Using the mixture of PEG-400 and TEOS as additive,membrane properties were optimized. Perfect performances could be obtained in the experimental range when the content of additives was 10% and the mass ratio of PEG-400 to TEOS was 6∶ 4.