【作者】 王淑梅；

【导师】 王湛；

【作者基本信息】 北京工业大学 ， 环境工程， 2003， 硕士

【摘要】 聚偏氟乙烯（PVDF）作为膜材料由于其疏水性而在应用中受到限制。本论文采用共混的方法，通过加入亲水性聚合物聚甲基丙烯酸甲酯（PMMA）和醋酸纤维素（CA）以提高PVDF膜材料的亲水性，并对PVDF/PMMA/CA制膜液体系的膜孔径均一化控制、凝胶机理和相分离机理进行了研究。通过正交实验，采用综合平衡法，以纯水通量、对牛血清白蛋白（BSA）的截留率和膜强度等性能为指标，最后得到具有较佳成膜性能的铸膜液组成和凝胶条件。对于PVDF/PMMA/CA体系，在各因素中，共混比是影响膜性能的最重要因素，其次是凝胶组分和溶剂种类，凝胶组分含量对膜性能的影响较轻微，在确定固含量17%、添加剂N-甲基-2-吡咯烷酮（NMP）含量3%的情况下，当共混比PVDF/PMMA/CA=8:1:1、混合溶剂比DMF/CH3COOH=8:2时，在21(1℃的自来水中凝胶，可得到纯水通量为200mL/cm2·h（室温，0.2MPa），对0.5‰牛血清白蛋白的截留率大于96%的超滤膜。本文选用PVDF/PMMA/CA三元高分子组分共混体系具有一定的创新性。 本文还针对膜孔径均一化控制问题进行了初步讨论，提出了一种控制膜孔径的新方法——化学方法。即通过制膜液中溶剂冰醋酸同凝胶介质碳酸钠发生化学反应产生二氧化碳气体，可使膜孔径尺寸分布更均一，通过膜的SEM照片观察，膜孔控制在0.15～0.21(m范围内，未见国内外文献报道，具有一定创新性。通过润湿角的测定表明，通过共混确实使PVDF膜的亲水性得到了提<WP=4>高。研究表明虽然CA材料比PMMA更亲水，但共混体系中只要有PMMA的加入，该共混膜的润湿角就和纯PMMA膜的润湿角相接近，这是由于PVDF/PMMA/CA制膜液体系在自来水中发生分层凝胶的缘故。PMMA较低的分子量、较小的溶液粘性和较快的凝胶速度，这些都为分层凝胶的发生提供了可能性。最后采用红外衰减全反射法和干膜撕裂法，分别从微观和宏观上证实了分层的存在。关于分层凝胶理论，近十年内的文献没有正式提出这一概念，具有一定的创新性。本文最后研究了PVDF/PMMA/CA制膜液体系在最佳组成（指固定最佳共混比、溶剂混合比和添加剂）时的浊点相图，该体系的热力学分相过程属于贫聚合物相成核生长机理。更多还原

【Abstract】 Due to its hydrophobicity, the application of PVDF membrane was limited. In this paper, poly(methyl methacrylate) (PMMA) and cellulose acetate (CA) were introduced to hydrophilize PVDF membrane by the way of blend. What’s more, the control of membrane pore size and the theory of gel and phase separation were also investigated. Firstly, the optimum composition and conditions for preparing PVDF membrane were obtained by square-crossing test whose indications were the pure water flux, the rejection for BSA and membrane strength. The membrane was prepared with higher pure water flux of 200 mL/cm2·h and better rejection of more than 96% for BSA, When the casting membrane solution, which was with the content of polymer 17%, the content of additive (NMP) 3%,the blend ration of PVDF/PMMA/CA and DMF/CH3COOH respectively 8:1:1 and 8:2, gel in the tap water.Secondly, a new method controlling membrane pore size, the chemical way，was brought forward in the paper. And a conclusion was drawn: it contributed to the solvent out of the casting membrane solution and made phase separation take place instantaneously that glacial acetic acid reacted with Na2CO3. Then the narrow distribution of membrane pores size with 0.15～0.21(m could be obtained. In addition, the hydrophilicity of membrane was characterized by the contact angle and results showed that the hydrophilicity of blend membranes was close to that of PMMA membrane if PMMA was contained in casting solution though CA was<WP=6>more hydrophilic than PMMA. This was mainly resulted from the delamination gel which was proved by the ultrared ATR spectrum and photo of teared dry membrane.Finally, the phase graph of the optimum composition of PVDF/PMMA/CA system was simply studied. Results indicated that the theory of phase separation for PVDF/PMMA/CA system belonged to poor polymer nucleus growth and the membrane structure with finger state pore was gained at last.To sum up, the innovations in my paper mainly included the choice of PVDF/PMMA/CA, the studies on the control of pore size and the theory of delamination gel.更多还原