热致相分离法EVOH EVOH平板膜制备及性能研究

发布时间：2018-03-13 11:31

本文选题：乙烯-乙烯醇共聚物　切入点：热致相分离法　出处：《天津工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：膜分离技术以其操作简单、节能、高效、无二次污染、可常温下连续操作等优点广泛应用于化工、医药、水处理等领域。目前已经工业化的高分子膜材料如聚丙烯、聚乙烯、聚偏氟乙烯等,具有优良的化学稳定性和热稳定性,但其亲水性较差,在实际应用中易吸附蛋白质等小分子污染物,降低膜分离效率,缩短膜使用寿命。乙烯-乙烯醇共聚物(EVOH)是一种半结晶的无规共聚物,其中聚乙烯醇链段赋予EVOH优异的亲水性能,使其抗污染性明显优于聚丙烯、聚乙烯、聚偏氟乙烯等。本文以EVOH为成膜聚合物,设计聚合物成膜体系,采用热致相分离法(TIPS)研究具有多孔结构的EVOH平板膜。首先,以EVOH为成膜聚合物,以丙三醇和聚乙二醇(PEG600)组成混合稀释剂,采用TIPS法制备了EVOH平板膜。研究了稀释剂组成对EVOH平板膜结构与性能的影响。结果表吸,当混合稀释剂中PEG600与丙三醇的质量分数比为7：3、5：5时,所得膜横截面为海绵状孔结构,当PEG600与丙三醇的质量分数比为3：7时,膜的横截面出现规则的球晶结构。随稀释剂中丙三醇含量增加,膜的纯水通量降低,对牛血清蛋白(BSA)的截留率增加。其次,以EVOH为成膜聚合物,以丙三醇和PEG600组成混合稀释剂,聚乙烯吡咯烷酮(PVP)为成孔剂,采用TIPS法制备了EVOH平板膜。研究了聚合物浓度和成孔剂对EVOH平板膜结构与性能的影响。结果表明,所得EVOH平板膜为具有海绵状孔的均质膜结构,随聚合物浓度的增加,膜表面及断面孔径减小,孔隙率以及纯水通量降低,BSA截留率升高,截留率可达89%以上。当加入PVP为0.5wt%时,与未添加时相比,纯水通量略有改善,BSA溶液截留率、平均孔径与孔隙率变化不大。最后,以EVOH为成膜聚合物,以丙三醇和PEG600组成混合稀释剂,以纳米二氧化硅(Si02)为添加剂,采用TIPS法制备了EVOH/SiO2杂化膜。研究了添加剂Si02对EVOH平板膜结构与性能的影响。结果表明,随Si02含量增加,膜平均孔径与孔隙率呈先增大后减小的趋势,断裂强度提高而断裂伸长率降低。当Si02含量为0.5wt%时,所得膜性能较好,其孔隙率为74.0%,平均孔径为0.5μm,纯水通量可达511 L·m-2·h-1,对BSA截留率可达88%以上,断裂强度为3.5MPa,断裂伸长率为21.7%。
[Abstract]:Membrane separation technology is widely used in chemical industry, medicine, water treatment and other fields because of its advantages of simple operation, energy saving, high efficiency, no secondary pollution, continuous operation at room temperature and so on. Polyvinylidene fluoride (PVDF) has excellent chemical stability and thermal stability, but its hydrophilicity is poor. In practical application, it is easy to adsorb small molecule pollutants such as protein, and reduce the efficiency of membrane separation. Ethylene-ethylenol copolymer (EVOH) is a semi-crystalline random copolymer, in which the polyvinyl alcohol chain gives EVOH excellent hydrophilicity, making it obviously superior to polypropylene and polyethylene. Polyvinylidene fluoride (PVDF) was used as the film forming polymer in this paper. In this paper, EVOH was used as the film forming polymer, and the EVOH flat membrane with porous structure was studied by thermal phase separation method. Firstly, EVOH was used as the film forming polymer. EVOH flat membrane was prepared by TIPS method with mixed diluent composed of glycerol and polyethylene glycol PEG600. The effects of diluent composition on the structure and properties of EVOH flat membrane were studied. When the mass fraction ratio of PEG600 to propanediol is 7: 3 / 5: 5, the cross-section of the film is a spongy pore structure, and when the mass ratio of PEG600 to glycerol is 3: 7, Regular spherulite structure appeared in the cross section of the membrane. With the increase of glycerol content in the diluent, the pure water flux of the membrane decreased, and the rejection rate of bovine serum protein (BSA) increased. Secondly, EVOH was used as the film forming polymer, and the mixed diluent was composed of propanol and PEG600. Polyvinylpyrrolidone (PVP) was used as pore forming agent to prepare EVOH flat membrane by TIPS method. The effects of polymer concentration and pore-forming agent on the structure and properties of EVOH flat membrane were studied. The results showed that the obtained EVOH flat membrane had a homogeneous membrane structure with sponge pore. With the increase of polymer concentration, the pore size and pore size of the membrane surface and section decrease, the porosity and the pure water flux decrease, the retention rate of the membrane increases to more than 89%. When the addition of PVP is 0.5 wt%, compared with the unadded one, the pore size of the membrane decreases. Pure water flux improved the retention rate of BSA solution slightly, and the average pore size and porosity changed little. Finally, EVOH was used as film forming polymer, propyl triol and PEG600 as mixed diluent and nano-silica as additive. EVOH/SiO2 hybrid membrane was prepared by TIPS method. The effect of additive Si02 on the structure and properties of EVOH flat membrane was studied. The results showed that the average pore size and porosity of the membrane increased first and then decreased with the increase of Si02 content. When the content of Si02 was 0.5 wt%, the membrane had a good performance, with a porosity of 74.0 渭 m, an average pore size of 0.5 渭 m, a pure water flux of 511 L 路m -2 路h-1, a rejection rate of more than 88% to BSA, a fracture strength of 3.5 MPA and an elongation at break of 21.7m.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ051.893

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