表面活性剂对PVDF中空纤维膜成膜过程的影响

发布时间：2019-01-19 16:12

【摘要】：聚偏氟乙烯(PVDF)是一种结晶性聚合物,机械性能较好,是综合性能优良的膜材料,PVDF分离膜因分离效率高、能耗低等优点,越来越受到人们的重视,在分离领域得到了广泛的应用,但是传统的多孔膜在制备过程中很容易形成相对致密的皮层,影响其渗透性能,大大阻碍了它的应用,因此,调控分离膜结构进而改变分离膜的性能成为研究热点。实验采用溶液相转化法,通过在聚偏氟乙烯铸膜液中添加特定亲疏水平衡值(HLB)的复配表面活性剂Span80和Tween80,从而调控分离膜皮层的微观结构。提出一种表面活性剂对溶液相转化法聚合物浓相区的界面活化作用原理,研究了表面活性剂的亲疏水平衡偏移值(AHLB)对膜基本性能的影响。结果表明,溶液相转化制备多孔膜的过程中,铸膜液从稳定区向不稳定区过渡时,存在表面活性剂对聚合物浓相区的界面活化作用;当表面活性剂的HLB接近于10时,表面活性剂对聚合物浓相区界面的活化作用最大,获得了一种皮层开孔最多、本体阻力最小、最可几孔径向最大孔径偏移的分离膜;此外,与不加表面活性剂的分离膜相比,分离膜的纯水通量显著提高了 277%,达到1015 L/(h·m2)。实验通过固定表面活性剂的亲疏水平衡值(HLB)的大小(HLB=10),改变铸膜液中表面活性剂的含量,研究了表面活性剂的含量对膜基本性能的影响,例如分离膜的纯水通量、本体阻力、固化速度、孔隙率、孔径分布、SEM以及机械性能等;结果表明,类似临界胶束浓度原理,表面活性剂对于聚合物浓相区的界面活化作用,也存在临界值。随着铸膜液中表面活性剂的含量不断增大(0%-3%),分离膜的纯水通量逐渐升高,皮层开孔增多;在这过程中,当表面活性剂的含量达到1.5%,纯水通量达到1015 L/(h.m2),皮层开孔最多,继续增大表面活性剂的含量,膜透水通量和皮层开孔数量都不再明显变化。本文提出了一种新的皮层结构控制方法,涉及到了一种新型的NIPS成膜机理,对于进一步研究溶液相转化法成膜机理有一定的帮助。
[Abstract]:Polyvinylidene fluoride (PVDF) is a crystalline polymer with good mechanical properties and excellent comprehensive properties. Because of its high separation efficiency and low energy consumption, poly (vinylidene fluoride) (PVDF) has attracted more and more attention. It has been widely used in the field of separation, but the traditional porous membrane is easy to form a relatively dense cortex during the preparation process, which affects its permeability and greatly hinders its application. It has become a hot research topic to regulate the structure of separation membrane and change the performance of separation membrane. The solution phase inversion method was used to regulate the microstructure of the membrane cortex by adding Span80 and Tween80, to the solution of polyvinylidene fluoride (PVDF) casting membrane with special hydrophobic equilibrium value (HLB). The principle of surfactant interface activation in solution phase inversion method was proposed. The effect of hydrophobic equilibrium shift value (AHLB) of surfactant on the basic properties of the membrane was studied. The results show that in the process of preparing porous membrane by phase transformation of solution, there exists the interface activation of surfactant in the thick phase region of polymer during the transition of casting liquid from the stable region to the unstable region. When the HLB of the surfactant is close to 10:00, the surfactant has the largest activation effect on the interface of the polymer in the dense phase region, and a separation membrane with the most cortical pore opening, the smallest bulk resistance and the best migration of the pore size to the maximum pore size is obtained. In addition, compared with the membrane without surfactant, the pure water flux of the membrane increased by 277L / (h ~ 2) to 1015 L / (h ~ 2). The hydrophobic equilibrium value (HLB=10) of fixed surfactant was determined to change the content of surfactant in casting solution. The effect of surfactant content on the basic properties of the membrane was studied, such as the pure water flux of the membrane. Bulk resistance, curing rate, porosity, pore size distribution, SEM and mechanical properties; The results show that, similar to the critical micelle concentration principle, there is a critical value for the interfacial activation of polymer dense phase region by surfactants. With the increasing of surfactant content (0-3%), the pure water flux of the membrane increased and the opening of the cortex increased. In this process, when the surfactant content reaches 1.5g, the pure water flux reaches 1015 L / (h.m2), the cortical pore opening is the most, and the surfactant content continues to increase, the membrane permeation flux and the cortical pore number do not change obviously. In this paper, a new control method of cortical structure is proposed, which involves a new mechanism of NIPS film formation, which is helpful to further study the mechanism of solution phase inversion method.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.893

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