高温NIPS法制备PVC微孔膜及其结构控制的研究

发布时间：2018-02-05 04:34

本文关键词： 聚氯乙烯（PVC）高温相转化法混合溶剂添加剂共混　出处：《华东理工大学》2011年硕士论文　论文类型：学位论文

【摘要】：本文利用高温相转化法制备了聚氯乙烯(PVC)平板微孔膜,研究了PVC成膜过程中的热力学和动力学影响因素,提出了较为系统的膜结构控制方法,通过采用不同添加剂,以及共混的方法改善了PVC微孔膜的亲水性能。首先,采用高温NIPS法,以水溶性酯γ-丁内酯(GBL)与常用溶剂N,N-二甲基乙酰胺(DMAc)作为混合溶剂,通过计算此混合溶剂体系与PVC的溶度参数差,判断铸膜液的热力学稳定性,结果表明随着γ-丁内酯的含量升高,溶解度参数差△δs-p逐渐升高,铸膜液的热力学稳定性逐渐降低。同时实验表明：随着DMAc/GBL质量比增大,膜表面孔增多,整个膜截面结构由海绵状逐渐在靠近水的一侧形成指状孔,机械性能降低。其次,在固定混合溶剂DMAc/GBL=1/1的基础上,讨论了PVC浓度,铸膜液温度,以及聚乙烯吡咯烷酮(PVPK90)的加入对膜性能和结构的影响。结果表明：PVC浓度的降低提高了孔隙率和水通量,铸膜液温度的提高降低了孔隙率,但提高了水通量。PVP的加入提高了溶剂和非溶剂的交换速度,指状孔逐渐转化成锥形孔,膜表面开孔变小,并形成了致密的皮层,膜的通量和截留率增大。然后,固定PVC浓度为20wt.%,采用GBL作为溶剂,聚乙二醇(PEG400)作为添加剂,研究了添加剂PEG比例对膜结构和性能的影响。实验结果表明：当PEG添加剂比例从10wt.%升高到30wt.%,膜的断面由指状孔转变为海绵状结构,膜的表面在放大10000倍的情况下没有明显的开孔结构。且PEG含量较大的膜具有更好的亲水性。随着添加剂PEG含量的增大,膜的孔隙率升高,但是膜的纯水通量没有很大的提高。在此基础上,改变凝胶浴浓度,由纯水转变成50wt.%GBL溶液,95wt.%GBL溶液。随着凝胶浴浓度的提高,膜的沉淀速率逐渐变慢,膜的断面维持在海绵状的结构。经95wt.%GBL溶液沉淀成膜后的膜表面开始产生了明显的微孔结构,水通量有了很大的提高,该组膜的断裂强度维持在6.5MPa左右。最后,使用20wt.%PEG400为添加剂50wt.%GBL作为溶剂,考察PVC/PVB共混比对成膜的影响。随亲水性高聚物PVB的引入,PVC的亲水性明显增强,膜外表面光滑平整不易收缩起皱。从SEM照片可以看出,PVB含量增大导致膜表面的平均孔径减小,开孔率增大,断面由海绵状转变为网状结构。且随着PVB含量的升高,膜的孔隙率由71.6%提高到80.8%,纯水通量由10L/(m2·h·bar)增加至30L/(m2·h·bar),对牛血清蛋白的截留率均在95%左右。同时该组膜显示出了很好的机械性能,断裂强度均在5Mpa以上
[Abstract]:In this paper, polyvinyl chloride (PVC) flat microporous membranes were prepared by high temperature phase inversion method. The thermodynamic and kinetic factors affecting the process of PVC film formation were studied, and a more systematic method of membrane structure control was put forward. The hydrophilicity of PVC microporous membranes was improved by using different additives and blending methods. Firstly, the high temperature NIPS method was used in which water soluble ester 纬 -butyrolactone (GBL) and common solvent N- (N-dimethyl acetamide) were used as the mixed solvent. The thermodynamic stability of the casting solution was determined by calculating the solubility parameter difference between the mixed solvent system and PVC. The results showed that the solubility parameter difference 未 s-p increased with the increase of 纬 -butyrolactone content. The thermodynamic stability of the casting solution decreased gradually, and the experimental results showed that with the increase of the mass ratio of DMAc/GBL, the pore on the membrane surface increased. The whole membrane cross section structure gradually formed finger hole near the water side from the sponge shape, and the mechanical properties decreased. Secondly, on the basis of fixed mixed solvent DMAc/GBL=1/1, the concentration of PVC and the temperature of casting solution were discussed. The effect of PVPK90) on the properties and structure of the membrane was studied. The results showed that the decrease of the concentration of 1: PVC increased the porosity and water flux, and the increase of casting temperature decreased the porosity. However, the increase of water flux. PVP increased the exchange rate between solvent and non-solvent. The finger-like pores were gradually converted into conical pores, and the membrane surface pores became smaller, and formed a dense cortex. The flux and retention of the membrane increased. Then, the concentration of PVC was fixed at 20 wt. with GBL as solvent and PEG400 as additive. The effect of additive PEG ratio on the structure and properties of the membrane was studied. The experimental results showed that when the additive ratio of PEG increased from 10wt.% to 30wt.%. The section of the membrane changed from finger pore to spongy structure. The surface of the membrane has no obvious open pore structure at 10000 times magnification, and the membrane with higher PEG content has better hydrophilicity. With the increase of PEG content, the porosity of the membrane increases. However, the pure water flux of the membrane was not greatly improved. On this basis, the gel bath concentration was changed from pure water to 50 wt.GBL solution. With the increase of the concentration of gel bath, the precipitation rate of the membrane becomes slower and slower. The membrane section is maintained in the spongy structure. The membrane surface formed by 95 wt.GBL solution precipitates the membrane surface to produce the obvious micropore structure, and the water flux has been greatly improved. The fracture strength of the film is about 6.5 MPA. Finally, using 20wt.PEG400 as additive and 50wt.GBL as solvent, the effect of PVC/PVB blending ratio on membrane formation was investigated. With the introduction of hydrophilic polymer PVB. The hydrophilicity of PVC was obviously enhanced, and the smooth surface of the membrane was smooth and easy to shrink and wrinkle. From the SEM photos, it can be seen that the increase of the content of PVC leads to the decrease of the average pore size of the membrane surface and the increase of the opening rate. The section changed from spongy to reticular structure, and with the increase of PVB content, the porosity of the membrane increased from 71.6% to 80.8%. The pure water flux increased from 10 L / m 2 路h 路h 路barto 30 L / m 2 路h 路h 路bar. The rejection rate of bovine serum protein was about 95%. Meanwhile, the membrane showed good mechanical properties, and the breaking strength was above 5Mpa.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TQ028.8

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