水蒸汽诱导时间对疏水性PVDF膜结构与性能的影响

Influence of vapor induction time on morphology and performance of PVDF porous membrane

以聚偏氟乙烯（PVDF）/N,N二甲基乙酰胺（DMAc）/正辛醇/水为制膜体系,采用粗糙基底辅助相转化法制备PVDF疏水性多孔膜。考察了水蒸汽诱导时间对膜结构、表面浸润性和透过性能的影响。结果表明,水蒸汽诱导时间延长,膜表面孔数量增多,孔径增大,膜底面的菜花状球晶粗化愈加充分,表面侧的海绵状网络孔逐渐疏松,当时间延至8min,膜底面球晶变得致密,晶核直径增大,表面侧海绵状网络孔结构中有滴状大孔出现;膜底面的疏水性随水蒸汽诱导时间先增大后明显降低,而气通量则在较短时间内增大明显,后略有下降;实验范围内较适宜的水蒸汽诱导时间为4~5min。

Hydrophobic polyvinylidene fluoride（PVDF）membrane was tailored by non-solvent induced phase inversion assisted with coarse substrate.N,N-dimethylacetamide（DMAc）and octanol were used as solvent and non-solvent addition,respectively.In this method,the polymer dope solution was cast on coarse substrate and the film was put in a higher relative humidity space for a fixed time interval,which was named vapor induction time.Then,it was immersed into water coagulation bath.The effects of vapor induction time on the morphology,hydrophobicity and permeability of membrane were investigated.As the vapor induction time increased,the number of top surface pores and pore size increased and the crystalline particles of bottom surface grew better.The spongy structure on the side of top surface became looser.When the vapor induction time extended to 8min,the crystalline particles on the bottom surface became denser and the diameter of particles increased.Blob-like holes appeared on cross section near the side of top surface.The hydrophobicity of the bottom surface increased and then decreased obviously with increasing the vapor induction time.The nitrogen flux increased obviously and then decreased slightly with increasing the vapor induction time.The suitable vapor induction time was 4~5min under experimental ranges.