聚丙烯中空纤维微滤膜结构调控及亲水化改性研究

发布时间：2018-03-31 00:37

本文选题：聚丙烯　切入点：热致相分离　出处：《上海大学》2016年博士论文

【摘要】：聚丙烯(PP)中空纤维膜因其具有良好的化学稳定性和热稳定性,且价格低廉,处理效率高,已经被广泛应用于膜蒸馏、工业废水及市政污水处理、饮用水净化等领域。由于PP为非极性结晶聚合物,常温下无合适溶剂,因此只能采用熔纺-拉伸法(MSCS)和热致相分离法(TIPS)制备中空纤维膜,其中TIPS法制备PP中空纤维微滤膜易实现对膜孔结构调控。PP中空纤维膜结构调控的关键因素是稀释剂和PP之间的相互作用力,由于单一稀释剂和PP作用力强,制备的膜一般为球状粒子结构,强度低,皮层厚,通量小,不适合用于水处理。本论文采用组合稀释剂通过TIPS法制备PP中空纤维膜,成功的实现了对PP中空纤维膜孔结构的调控,并对PP进行了多种亲水改性,制备了具有亲水性的PP中空纤维膜。研究TIPS法制备PP中空纤维膜聚合物浓度、组合稀释剂与PP的相互作用力、制膜工艺参数等因素与中空纤维膜结构和性能之间的关系。膜丝强度结果表明在组合稀释剂DS/GA体系下PP含量为20%较为合适。等温冷却过程为L-L(液-液)分相的喷丝液在TIPS法制备PP中空纤维膜过程中由于冷却速率快,体系易直接进入结晶区域而出现S-L(固-液)分相,所得的结构为球状粒子结构。通过提高气隙长度来降低冷却速率,出现了L-L相分离的网状孔结构,说明非等温冷却动力学过程对喷丝液体系分相过程的影响较大。在常温水浴冷却下,聚合物浓度为20%,组合稀释DS/GA质量比为10:5~10:6之间的喷丝液体系发生了相分离形式的转变,由S-L相分离到L-L相分离的转变,膜孔结构也出现明显的球状粒子-网状孔-蜂窝空结构的转变。同时发现芯液与喷丝液的传质会影响内皮层的开孔性;喷丝液中水溶性溶剂的加入也会改善喷丝液与凝固浴的传质,从而改善外皮层的开孔性。通过TIPS法制备了PP亲水改性中空纤维膜。试结果表明,含5份聚醚醇类亲水改性剂HL560的PP的水接触角降低到20°左右,但浸泡后会提高到60°以上。为解决水处理过程中亲水改性剂流失问题,采用驻留剂EAA钠盐和亲水改性剂复配改性PP,亲水改性PP的亲水性能明显提高并能长时间保持。膜的纯水通量由原来的122 l/m2h提高到200 l/m2h。此外,EAA钠盐的加入会轻微影响PP的结晶性能,改性膜的结构稍微有所改变,但影响不大。通过DSC、XRD等方法研究了PP/PA6合金的非等温结晶动力学,从而研究了PA6的加入对PP结晶性能的影响,为TIPS法制膜提了供理论依据。实验结果表明无定型PA6和PP共混,PA6含量25wt%,以10%wt的PP-g-MAH作为相容剂制备的PP/PA6合金,相容性优良,几乎没有改变PP的结晶性能,还促进了PP的β晶形成。制备的PP/PA6合金中空纤维膜在PA6含量为25wt%以下时,结构几乎和PP膜相同,亲水性能明显改善,膜丝强度也有所提高。
[Abstract]:Polypropylene (PP) hollow fiber membrane due to its good thermal and chemical stability, and low price, high processing efficiency, has been widely used in membrane distillation, industrial wastewater and municipal wastewater treatment, drinking water purification and other fields. Since PP is a non polar crystalline polymer, no suitable solvent at room temperature, it can only be by melt spinning stretching (MSCS) and thermally induced phase separation (TIPS) preparation of hollow fiber membrane, the preparation of TIPS PP hollow fiber microfiltration membrane is easy to realize the key factors on the membrane pore structure control of.PP hollow fiber membrane structure regulation is the interaction between the dilution agent and PP, due to the single diluent and PP the force is strong, the membrane prepared is generally spherical particle structure, low intensity, cortical thickness, small flux, not suitable for water treatment. The preparation of PP hollow fiber membrane by TIPS method using a combination of diluent, the successful implementation of the PP hollow fiber The regulation of fiber membrane pore structure, and the PP in a variety of hydrophilic modification of PP hollow fiber membrane with a hydrophilic preparation. Study on Preparation of TIPS PP hollow fiber membrane polymer concentration, diluent and PP combination of interaction, the relationship between the structure and the performance of the membrane preparation process parameters and hollow fiber membrane the membrane strength. The results show that the combination of thinner DS/GA system 20% PP content is more appropriate. The isothermal cooling process for L-L (liquid) liquid phase in TIPS spinning preparation of PP hollow fiber membrane process due to the rapid cooling rate, easy system directly into the crystal region and S-L (solid and liquid) the phase structure of spherical particle structure. To reduce the cooling rate by increasing the length of air gap, the mesh pore structure of L-L phase separation, that influence the kinetics of non isothermal cooling spray fluid system greatly. The process of phase separation in water at room temperature The cooling bath, the polymer concentration is 20%, combination of dilution DS/GA mass ratio of spinneret fluid system between 10:5~10:6 phase separation occurred in the form of change, the phase separation of S-L into L-L phase separation, membrane pore structure also appears spherical particles - obvious netted hole honeycomb hollow structure change. At the same time that mass transfer the core liquid and the spinning liquid will affect the endothelial layer hole of spinneret; join the water soluble solvent will improve the mass transfer of spinneret and coagulation bath liquid, thereby improving the outer layer hole. TIPS PP was prepared by hydrophilic hollow fiber membrane. The test results show that containing 5 copies of polyether alcohols hydrophilic modifier HL560 PP water contact angle decreased to about 20 degrees, but after immersion will increase to more than 60 degrees. In order to solve the water treatment process of hydrophilic agent loss, the resident agent EAA sodium and hydrophilic agent modified PP hydrophilic hydrophilic modification PP The performance improved significantly and can keep a long time. The pure water flux increased from 122 l/m2h to 200 l/m2h. in addition, adding EAA sodium will slightly affect the crystallization of PP, the structure of the modified membrane slightly changed, but the effect is not obvious. By DSC, the non isothermal crystallization kinetics of XRD PP/PA6 alloy have been studied. Thus, the effect of PA6 on the crystallization of PP, provide a theoretical basis for the TIPS technique. The experimental results show that the amorphous PA6 and PP blend, the content of PA6 25wt%, 10%wt PP-g-MAH PP/PA6 alloy as compatibilizing agent preparation, excellent compatibility, almost no change in the crystallinity of PP also. Promote the beta crystal formation of PP alloy. PP/PA6 hollow fiber membrane prepared in the PA6 content of 25wt%, PP and almost the same membrane structure, hydrophilic properties improved significantly, the membrane strength is also improved.

【学位授予单位】：上海大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ051.893

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