Polyvinylidene fluoride (PVDF) porous membranes were prepared by a two-step method of surface gelation-immersion precipitation phase inversion. The effects of spraying CS solution concentrations on the structure and properties of membranes were investigated. The results showed that with the concentration increasing of CS solution spraying on the surface of the casting solution film, the porosity of PVDF membranes gradually increased, the mean pore diameter of membranes firstly increased and then reduced, the surface contact angle decreased, and β crystal content in the top surface of membranes gradually decreased. The top surface of membrane without spraying CS solution displayed a dense structure, while the top surface of membranes after spraying CS solution exhibited a porous structure, while the cross-sectional structure of all membranes was composed of the finger-like voids. When the concentrations of spraying CS solution increased, the water flux of membranes firstly increased and then decreased.

中文翻译：

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不同浓度喷洒壳聚糖溶液对PVDF多孔膜结构和性能的影响

采用表面凝胶-浸渍沉淀相转化两步法制备了聚偏二氟乙烯（PVDF）多孔膜。研究了喷洒 CS 溶液浓度对膜结构和性能的影响。结果表明，随着浇铸液膜表面喷洒CS溶液浓度的增加，PVDF膜的孔隙率逐渐增大，膜的平均孔径先增大后减小，表面接触角减小，β晶膜上表面的含量逐渐减少。未喷CS溶液的膜顶面呈现致密结构，喷CS溶液后的膜顶面呈现多孔结构，而所有膜的横截面结构均由指状空隙组成。随着喷洒CS溶液浓度的增加，膜的水通量先增大后减小。