多孔中空纤维膜制备及后处理对膜性能的影响

采用干-湿法纺丝工艺,以N,N-二甲基乙酰胺为溶剂,聚乙烯吡咯烷酮(PVP)为添加剂,制备聚偏氟乙烯/聚氯乙烯/聚甲基丙烯酸甲酯共混五孔中空纤维膜,研究了纺丝工艺参数以及后处理对膜性能的影响.结果表明,当干纺程为20 cm,芯液中DMAC质量分数为40%,芯液流量为13 mL/min时,制备的纤维膜综合性能最好.该中空纤维膜最大水通最为612 L/(m2·h),截留率为83%.     

添加剂对聚偏氟乙烯成膜过程的影响

以聚偏氟乙烯(PVDF)为膜材料,聚乙烯吡咯烷酮(PVP)为添加剂,N,N-二甲基乙酰胺(DMAc)为溶剂,采用浸没沉淀相转化法制备聚偏氟乙烯超滤膜。本实验主要研究了添加剂聚乙烯吡咯烷酮对铸膜液黏度的影响。通过浊点测试分析了铸膜液体系的热力学性质。同时对添加剂与熟化温度、熟化时间对铸膜液及膜性能的影响做了初步的探讨。     

基于流变特性探讨聚芳砜酰胺纺丝液的稳定性

利用旋转流变仪研究了聚芳砜酰胺(PSA)纺丝液的稳态和动态流变行为,结果表明:以二甲基乙酰胺(DMAc)为溶剂的聚芳砜酰胺溶液表现出典型的聚合物浓溶液流变特性,在低剪切速率区表现为牛顿流体特性,而随着剪切速率的增大,呈现出切力变稀行为,纺丝液的零切黏度、松弛时间随PSA特性黏度的增大而增大,非牛顿特性增强;证明了PSA纺丝溶液在测试温度范围内处于均质溶液状态,在进一步的动态温度扫描分析中,没有发现溶液的凝胶化转变现象,说明在试验温度范围内,PSA纺丝液处于均质稳定状态。     

聚砜中空纤维超滤膜制备及性能

以聚砜(PSU)为成膜聚合物,聚乙烯吡咯烷酮(PVP)为成孔添加剂,二甲基乙酰胺为溶剂,采用干–湿法纺丝工艺和浸没沉淀相转化法制备了PSU中空纤维膜,研究了添加剂含量、凝固浴温度、干纺程对中空纤维膜结构与性能的影响。结果表明,随着添加剂PVP含量的增大,在PSU中空纤维膜表皮层形成贯通膜孔,皮层变薄,孔径变大,指状孔发达,水通量提高,截留率下降;凝固浴温度升高对膜水通量起到一定的抑制作用,凝固浴温度为30℃时,制得的膜具有较高的水通量和卵清蛋白截留率,以及较高的孔隙率;干纺程的大小对膜性能有重要影响,当干纺程为11 cm时,膜纯水通量为200 L/(m~2·h),截留率为90%,综合性能较好。     

以DMAc为溶剂的腈纶干法纺丝工艺

二甲基甲酰胺(DMF)是良好的纺丝溶剂，因其毒性被限制在腈纶干法纺丝中使用。二甲基乙酰胺(DMAc)是腈纶湿法纺丝的溶剂，但其溶解度参数比DMF略低，溶解性低于DMF。同时受腈纶干法纺丝原液固含量远高于湿法纺丝原液固含量的影响，DMAc溶剂配制相同固含量的聚丙烯腈，溶解性会降低。通过对聚丙烯腈溶解性、溶剂扩散、溶剂回收、设备腐蚀、纤维结构性能等方面的研究，确定了以DMAc为溶剂的干法腈纶的聚合物特性黏度、原液固含量、溶解时间和温度、纺丝、溶剂回收等关键工艺，实现了以DMAc为溶剂的腈纶干法工艺安全稳定运行，污水和操作现场溶剂残留大幅度降低，操作环境得到显著改善。     

不同铸膜液成分对PES/PVDF膜结构与性能影响的研究

采用浸没沉淀相转化法,以二甲亚砜(DMSO)、磷酸三乙酯(TEP)及二甲基乙酰胺(DMAC)作为铸膜溶剂,制备聚醚砜(PES)/聚偏氟乙烯(PVDF)共混膜,研究不同铸膜液成分对膜结构与性能的影响。通过膜的纯水通量、孔隙率、接触角等表征膜性能。利用有机添加剂N-甲基吡咯烷酮(NMP)、聚乙烯吡咯烷酮(PVP)改变PES/PVDF共混膜的性能,结果表明无机添加剂可增大其纯水通量和孔隙率并改善其亲水性。     

聚砜中空纤维支撑膜结构对复合膜性能的影响

聚砜、乙二醇单甲醚和二甲基乙酰胺的溶液通过环形喷丝嘴,其芯液为水溶液,通入二甲基乙酰胺的水溶液,制得聚砜中空纤维支撑膜。中空纤维浸入室温固化的硅橡胶有机溶剂的溶液中,制得聚砜中空纤维—硅橡胶的富氧复合膜。研究了聚砜的固含量,添加剂的种类和用量以及芯液等对富氧复合膜的透气速率和分离系数的影响。     

非溶剂添加剂对聚醚砜酮中空纤维纳滤膜结构和性能的影响

以新型杂萘联苯聚醚砜酮(PPESK)为膜材料,N-甲基-2-吡咯烷酮(NMP)为溶剂,乙二醇甲醚(EGME)、冰醋酸(AA)以及AA/EGME作为复合添加剂,采用干-湿相转化技术制备了中空纤维非对称纳滤膜,重点考察了非溶剂添加剂对中空纤维膜结构和性能的影响。结果表明非溶剂添加剂的加入导致了中空纤维膜孔结构由指状转变为海绵状,从而引起中空纤维膜性能的变化。当聚合物质量分数为23%,铸膜液溶剂体系为m(AA)∶m(EGME)∶m(NMP)=5.7∶16.5∶54.8时,中空纤维膜对PEG600的截留率高于96%,纯水通量为211 L/(m2.h)。     

添加剂PVP、PEG对PVDF/PVP(PEG)/DMAc铸膜液扩散性质的影响

采用浸入沉淀相转化和铸膜液光透射测试相结合的方法,考察了添加剂聚乙烯吡咯烷酮(PVP)和聚乙二醇(PEG)对聚偏氟乙烯(PVDF)/ PVP(PEG)/二甲基乙酰胺(DMAc)铸膜液的扩散性质的影响.实验中改变了PVP添加剂的含量和PEG添加剂的分子量.结果表明,PVDF铸膜液浸入沉淀过程初始阶段的溶剂外扩散符合费克扩散定律.无添加剂时体系溶剂的表观扩散系数为52.52×10-6 g·s-1/2,添加5% PVP或PEG20000时其系数分别为17.11和22.53×10-6 g·s-1/2,即添加PVP、PEG使PVDF铸膜液的溶剂外扩散速率下降.同时从光透射实验可知,上述添加剂的加入使非溶剂向内扩散的速率上升.实验表明,溶剂外扩散受控于体系的粘度,非溶剂的向内扩散受控于界面的亲水性.研究还改进了浸入沉淀相转化法的实验方法,克服了原有方法的弊端,有助于获得更多扩散行为信息.     

聚醚砜质量分数对聚偏氟乙烯/聚醚砜共混膜性能和结构的影响

用与聚醚砜共混的方法来改善聚偏氟乙烯膜的抗收缩性能,以二甲基乙酰胺作溶剂,聚乙烯吡咯烷酮为添加剂,研究了聚醚砜(PES)质量分数对聚偏氟乙烯/聚醚砜共混膜的收缩率、水通量、截留率及形态结构的影响。聚醚砜的加入可以有效地降低共混膜的收缩率,在w(PES)=1.5%时,共混膜的水通量取得极大值,截留率取得极小值。     

Investigation on the effect of spinning conditions on the properties of hollow fiber membrane for hemodialysis application

Polyethersulfone (PES) hollow fiber membranes were fabricated via the dry‐wet phase inversion spinning technique, aiming to produce an asymmetric, micro porous ultrafiltration hollow‐fiber specifically for hemodialysis membrane. The objective of this study is to investigate the effect of spinning conditions on the morphological and permeation properties of the fabricated membrane. Among the parameters that were studied in this work are air gap distance, dope extrusion rate, bore fluid flow rate, and the take‐up speed. The contact angle was measured to determine the hydrophilicity of the fibers. Membrane with sufficient hydrophilicity properties is desired for hemodialysis application to avoid fouling and increase its biocompatibility. The influences of the hollow fiber's morphology (i.e., diameter and wall thickness) on the performance of the membranes were evaluated by pure water flux and BSA rejection. The experimental results showed that the dope extrusion rate to bore fluid flow rate ratio should be maintained at 1:1 ratio to produce a perfectly rounded asymmetric hollow fiber membrane. Moreover, the flux of the hollow fiber spun at higher air gap distance had better flux than the one spun at lower air gap distance. Furthermore, spinning asymmetric hollow fiber membranes at high air gap distance helps to produce a thin and porous skin layer, leading to a better flux but a relatively low percentage of rejection for BSA separation. Findings from this study would serve as primary data which will be a useful guide for fabricating a high performance hemodialysis hollow fiber membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43633.     

Removal of dyes by poly(p-phenylene terephthamide)/polyvinylidene fluoride hollow fiber in-situ blend membranes

In order to obtain the compatible poly(p-phenylene terephthalamide) (PPTA)/polyvinylidene fluoride (PVDF) blend membranes, the casting solution was synthesized via the in situ polycondensation process and flat sheet blend membranes were successfully prepared through the immersion precipitation phase inversion method in our previous study. In this study, the polycondensation solution was directly used as the spinning dope to fabricate PPTA/PVDF hollow fiber in-situ blend membrane by the dry-wet spinning technique. Hollow fiber membranes were employed to remove the dyes including Congo red (CR) and methylene blue (MB) from the dyeing liquor. Effects of operation conditions on dye rejection and membrane water flux were investigated. With the increase of operation pressure, feed concentration and feed temperature, dye rejection rates gradually decreased, but the rejection value of CR and MB still remained above 99.5%. On the contrary, the permeation water flux basically increased. During the continuous dye filtration of 300 min, hollow fiber membrane can maintain high dye rejection rates and stable water flux. The combination method of physical backwashing and chemical cleaning can effectively alleviate membrane fouling and recover membrane water flux. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48569.     

Two‐dimensional simulation of hollow fiber membrane fabricated by phase inversion method

In the steady fabricating process, two‐dimensional hollow fiber membrane near the spinneret was numerically simulated using the finite element method (FEM). The unknown positions of free surface and moving interface were calculated simultaneously by the velocity and pressure fields. The effects of seven relevant parameters, i.e., inertia term, gravity term, dope flow rate, bore flow rate, dope viscosity, tensile force, end velocity and non‐Newtonian on the velocity and diameter profile were studied. On the basis of the simulated results, the inertia term in hollow fiber‐spinning process was safely neglected in low speed, while the effect of gravity was not be neglected. Besides, the outer diameter of the fibers increased with an increase of dope flow rate and bore flow rate; Large tensile force or large end velocity could cause large deformation in the air gap; larger viscous dope solution tended to make less deformation in the air gap. It was found that an increase of the dope flow rate at small dope flow rate resulted in an increase of the inner diameter, while at large dope flow rate, it decreased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2067–2074, 2006     

Nanometric thin skinned dual‐layer hollow fiber membranes for dehydration of isopropanol

A novel sulfonated polyphenylsulfone (sPPSU)/polyphenylsulfone (PPSU)‐based dual‐layer hollow fiber membrane with a nanometric thin skin layer has been designed for biofuel dehydration via pervaporation. The thickness of skin selective layer is in the range of 15–90 nm under different spinning conditions measured by positron annihilation spectroscopy (PAS) coupled with a mono‐energetic positron beam. The effects of outer‐layer dope properties, coagulation temperature, and dope flow rate during spinning were systematically investigated. By tuning these spinning parameters, a high performance sPPSU/PPSU‐based dual‐layer hollow fiber membrane with desirable morphology was successfully obtained. Particularly owing to its nanometric thin skin layer, a high flux of 3.47 kg/m²h with a separation factor of 156 was achieved for dehydration of an 85 wt % isopropanol aqueous solution at 50°C. After post thermal treatment at 150°C for 2 h, the separation factor was dramatically improved to 687 while flux dropped to 2.30 kg/m²h, which make it comparable to the inorganic membranes. In addition, excellent correlations were found among the results from field emission scanning electron microscopy, PAS spectra, and separation performance. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2943–2956, 2013     

聚砜中空纤维超滤膜制备条件的考察

考察了膜液温度，内外凝胶温度和膜液出喷丝头的剪切速度对聚砜中空纤维超滤膜性能的影响。结果表明，保持其它条件一定时，膜液温度升高或凝胶温度降低时，最终膜孔径变小，并用制膜体系三元相图进行了分析，当膜液出喷丝头的剪切速度达到某一极限值时（不同膜液体系，此极限值不同），获得了压密性能优良的聚砜中空纤维超滤膜。     

Preparation of polysulfone hollow fiber affinity membrane modified with mercapto and its recovery properties. I. Synthesis and preparation of hollow fiber matrix membrane

Several kinds of chloromethyl polysulfones (CMPSF) with different chlorinity and reactive groups were synthesized by Friedel‐Crafts reaction, which could be utilized as reactively matrix membrane materials. The CMPSF hollow matrix membranes were prepared with phase inversion by utilization of the CMPSF/additive/DMAC casting solution and CMPSF as membrane materials. The rheological behavior of CMPSF/additives/DMAC spinning casting solution was studied. The experimental results showed that the spinning casting solution was a pseudoplastic fluid, the apparent viscosity of the spinning casting solution decreased with the increase of shearing rate, and the viscous flow activity energy of the spinning casting solution was inclined to unchange at high shearing rate. The effects of composition of spinning casting solution and process parameters of dry–wet spinning on the structure of CMPSF hollow fiber matrix membrane were investigated. The pore size, porosity, and water flux of membrane decreased with the increase of additive content, bore liquid, and dry spinning distance. With the increase of extrusion volume outflow, the external diameter, wall thickness, and porosity of the hollow fiber matrix membrane increased, but the pore size and water flux of the membrane decreased. It was also found that the effects of internal coagulant composition and external coagulant composition on the structure of CMPSF hollow fiber matrix membrane were different. The experimental results showed that thermal drawing could increase the mechanical properties of CMPSF hollow fiber matrix membrane and decrease the pore size, porosity, and water flux of the CMPSF hollow fiber matrix membrane, and the thermal treatment could increase the homogeneity and stability of the structure of the CMPSF hollow fiber matrix membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 758–771, 2006     

超高分子量聚丙烯腈溶液的流变性

本文研究了超高分子量聚丙烯腈—二甲基亚砜溶液的流变性能,探讨超高分子量聚丙烯腈(UHMW—PAN)的分子量、总固浓度及不同的毛细管长径比对纺丝原液的粘度、非牛顿流动指数、结构粘度指数、最大松弛时间的影响,并探讨了与原液可纺性的关系,为纺制高强高模聚丙烯腈纤维和能耐反冲洗的聚丙烯腈中空纤维膜提供了依据。     

Preparation and performances of poly(phthalazinone ether sulfone ketone) hollow fiber membranes with excellent thermotolerance

The cloud points of PPESK/NMP/H₂O ternary system at different temperatures were measured by titrimetric method. The binodal lines in the ternary phase diagram of the poly(phthalazinone ether sulfone ketone (PPESK) dope system was determined, on the basis of the cloud point experimental data being linearly fitted with the semiempirical linear cloud point correlation. Furthermore, phase separation behavior during the phase inversion of PPESK membrane‐forming system was discussed in terms of the phase diagram. Then, dry–wet spinning technique was employed in manufacturing PPESK hollow fiber membranes by immersion precipitation method. The cross‐section morphologies of hollow fibers were observed by scanning electronic microscopy. Also, the effects of dope solution composition and spinning parameters, including the coagulant composition and the spinning temperature on the separation performances of fibers, were evaluated by permeability measurements. The thermotolerance of the PPESK hollow fiber membranes prepared in the work was examined for the permeation operation at different temperatures and pressure differences. The experimental results showed that pure water flux increases several fold along with the temperature increases from 20 to 80°C at different operation pressures, while the solute rejection only decreases slightly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 878–884, 2006     

Porous polyethersulfone hollow fiber membrane in gas–liquid contacting processes

Porous polyethersulfone hollow fiber membranes were fabricated via dry–wet phase inversion method with the polymer concentration in the spinning dope either 13 wt% or 15 wt%. The fabricated hollow fiber membranes were characterized by different test methods and the performance of membranes in contactor applications was tested by CO₂ absorption. The mean pore size, effective surface porosity and membrane porosity decreased while the membrane density and Liquid Entry Pressure (LEPw) increased as polymer concentration increased. The CO₂ absorption flux of the fabricated membranes was measured in two cases; i.e. when the absorbent, distilled water, was in the lumen side or in the shell side. The CO₂ flux for the membrane, fabricated from 13 wt% PES solution, was compared with some commercial and in-house made membranes. The former membrane had 111% higher flux than a commercial PTFE membrane.     

聚丙烯腈中空纤维膜的研究

本文对聚丙烯腈中空纤维膜的原料组成，中空纤维的纺丝工艺与膜性能的关系，以及纺制不同结构中空纤维膜的纺丝工艺和方法进行了综述，提出了纺制耐热性好的聚丙烯腈中空纤维３膜可能的方法和意义。