聚乙二醇对聚醚砜微孔膜致孔作用的研究

以聚醚砜聚乙二醇溶剂为铸膜液体系、采用干湿相转化法制备微孔滤膜,研究了各种制膜条件对膜孔径结构的影响.实验发现聚乙二醇在体系中起到分散稳定的作用,只有到浓度大于70%时,才会对铸膜液的粘度产生明显影响,聚合物在铸膜液中的溶解状态也随之改变,进而影响膜的结构.不同溶剂NMP、DMF、DMAc、DMSO等极性溶剂或固体溶剂己内酰胺均可制得开孔率较高的微孔膜,但对膜的结构和性能影响差别不大.在本研究体系中,膜的结构取决于聚乙二醇、溶剂的浓度比例关系.     

The influence of phase inversion process modified by chemical reaction on membrane properties and morphology

In this study, the chemical reaction between acetic acid (CH₃COOH) used as non-solvent additive of casting solution and sodium carbonate (Na₂CO₃) dissolved in water as coagulant was employed to modify the classical phase inversion process. By means of this method, the polyethersulphone (PES) ultrafiltration (UF) membranes were prepared. The influence of acetic acid on the properties of the polymer solution was examined by viscometry and related to the morphology of the membrane prepared from the casting solution. The membranes were characterized in terms of the pure water flux, solute transport and field emission scanning electron microscope (FESEM) observation. It was found that chemical reaction between the additive and coagulant increases membrane permeability and mean pore size while maintaining the relatively narrow pore size distribution. FESEM images also confirmed that the chemical reaction contributes to suppress the formation of macrovoid and enhance the interconnectivity of pore. Furthermore, the potential mechanism of membrane formation influenced by chemical reaction was explored tentatively.     

Effect of nonsolvents on properties of spinning solutions and polyethersulfone hollow fiber ultrafiltration membranes

The relationship among the presence of nonsolvent additives, the rheological behavior of spinning solutions and properties of hollow fiber membranes was studied. The additives tested were water, polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG), and the base mixture was polyethersulfone/N-methyl-2-pyrrolidone (PES–NMP). In addition the effect of combining water and PVP or PEG was also studied. Membranes were prepared using a spinneret having two concentric orifices. The internal coagulant used as well as the nonsolvent from the coagulation bath were both water at 28°C and 30°C, respectively. Rheological properties of polymer solutions were evaluated using a rheometer Haake RV 20. Changes on composition of spin-solutions were also evaluated in terms of membrane water permeability, solute rejection and membrane structure observed using scanning electron microscopy (SEM). Experimental results from this work showed that spinning solutions containing any of the three additives behave as Newtonian fluids in the range of shearing rates tested. The addition of water, PVP or PEG to the base PES–NMP solution increased its viscosity and this effect was independent of the type of additive used. A direct relation between viscosity of casting solutions and membrane thickness was found. However, rheological properties (viscosity and normal stress difference) could not be used to explain differences on membrane water flux (MWF) when using different additives at the same concentration. The addition of any of the three additives generally increased MWF. The extent of this increment seemed to be more related to changes on membrane porosity than changes on pore sizes induced by the nature and concentration of the additive used.     

聚醚砜/酚酞基聚醚砜共混相容性及凝胶特性研究

采用混合热焓法和稀溶液粘度法预测了聚醚砜/酚酞基聚醚砜体系相容性,并观察了聚醚砜/酚酞基聚醚砜共混制膜液的凝胶值与共混比的关系.聚醚砜/酚酞基聚醚砜为部分相容体系,其相容性与组成有关.共混制膜液的凝胶值受共混组成的影响,并非纯组分制膜液凝胶值的线性加和.     

Polyurethane and sulfonated polysulfone blend ultrafiltration membranes. I. Preparation and characterization studies

Polyurethane (ether type) and sulfonated polysulfone (sodium salt form) in the presence of polyethylene glycol 600 were blended in various compositions using N,N'-dimethylformamide as solvent and used for preparing ultrafiltration membranes by the phase inversion technique. Polymer blend composition, additive concentration, and casting and gelation conditions were optimized. Blend membranes were subjected to ultrafiltration characterizations such as compaction, pure water flux, water content, and membrane resistance. The membranes were also subjected to the determination of pore statistics and molecular weight cutoff determination studies using dextran of different molecular weights. Surface morphology of the membranes was analyzed using scanning electron microscopy at different magnifications. The effects of polymer composition and additive concentration on the above parameters were analyzed and the results are compared and discussed with those of pure sulfonated polysulfone membranes. The derived pore size, porosity, and number of pores have a remarkable interrelationship and also have a definite role and relationship with the molecular weight cutoff, morphology, and flux performance of the membranes.     

酚酞基聚芳醚砜非对称超滤膜凝胶动力学研究

采用耐高温工程塑料——含酚酞侧基的聚芳醚砜(PES-C)为膜材料,草酸和聚乙二醇为添加剂,N,N-二甲基乙酰胺为溶剂,并利用改进的凝胶动力学实验装置和方法,使之能真实地再现不同膜孔结构生长及发展演化的过程,借助相关软件对图像进行处理,考察了添加剂、聚合物浓度对铸膜液凝胶速度的影响,对酚酞基聚芳醚砜非对称膜的凝胶过程的动力学进行研究.结果表明,动力学图像与最终膜结构有很好的一致性,凝胶动力学方面得到了与Strathman等不同的研究结果,发现凝胶前锋位移的平方与时间不是线性关系,凝胶动力学过程不能简单地用Fick扩散定律来描述.     

The effect of heat treatment of PES and PVDF ultrafiltration membranes on morphology and performance for milk filtration

The flat sheet polyethersulfone (PES) and poly(vinylidene fluoride) (PVDF) membranes were prepared by immersion precipitation technique. The influence of hot air and water treatment on morphology and performance of membranes were investigated. The membranes were characterized by AFM, SEM, cross-flow filtration of milk and fouling analysis. The PES membrane turns to a denser structure with thick skin layer by air treatment at various temperatures during different times. This diminishes the pure water flux (PWF). However the milk permeation flux (MPF) was considerably improved at 100 °C air treatment for 20 min with no change in protein rejection. The smooth surface and slight decrease in surface pore size for air treated PES membrane at 100 °C compared to untreated membrane may cause this behavior for the membrane. The water treatment of PES membranes at 55 and 75 °C declines the PWF and MPF and increases the protein rejection. This is due to slight decrease in membrane surface pore size. The treatment of PES membrane with water at higher temperature results in a porous structure with superior performance. The fouling analysis of 20 min treated membrane indicates that the surface properties of 100 °C air treated and 95 °C water treated PES membranes are improved compared to untreated membrane. The SEM observation depicts that the morphology of air and water treated PVDF membranes was denser and smoother with increasing the heat treatment temperature. The 20 min air treated PVDF membranes at 100 °C and water treated at 95 °C exhibited the highest performance and antifouling properties.     

Synthesis and characterization of asymmetric polyethersulfone membranes: effects of concentration and polarity of nonsolvent additives on morphology and performance of the membranes

In this study, effects of methanol, ethanol and 1‐propanol as variable nonsolvent additives (NSAs) on the morphology and performance of flat sheet asymmetric polyethersulfone (PES) membranes were investigated. The membranes were prepared from PES/Polyvinylpyrrolidone (PVP)/N‐methyl‐2‐pyrrolidone (NMP) system via phase inversion. The obtained results indicate that with the addition of NSAs to the casting solution, the membrane morphology changes slowly from macrovoids to an asymmetric structure with finger‐like pores. By increasing the NSAs concentrations in the casting solution and decreasing their polarities, the membrane structure changes from finger‐like pores to sponge. The AFM and SEM images reveal that addition of NSA to the casting solution decreases the pore size of the prepared membranes and reduces the pure water flux and BSA solution flux, while increasing the protein rejection. Surface analysis of the membranes showed that mean pore size and surface porosity of the prepared membranes with NSAs in the casting solution are smaller compared with those of the membrane prepared with no NSA. Pure water flux and BSA solution flux through the membranes decrease and BSA rejection increases with increase in the concentration of NSAs and decrease in their polarity. Finally, it can be concluded that the T_g values of the PES membranes increase by addition of NSAs to the casting solution. Copyright © 2009 John Wiley & Sons, Ltd.     

Protein-adsorption-resistance and permeation property of polyethersulfone and soybean phosphatidylcholine blend ultrafiltration membranes

Novel ultrafiltration membranes were prepared by simple blending of polyethersulfone (PES) and soybean phosphatidylcholine (SPC). X-ray photoelectron spectroscopy (XPS) and water contact angle measurements indicated SPC enrichment at the membrane surfaces. The immobilization and arrangement of PC groups at surfaces rendered the membranes more hydrophilic. BSA adsorption amount decreased from 56.2 μg/cm² for SPC-free PES membrane to 2.4 μg/cm² for PES/SPC blend membrane. The fouling-resistant property of the blend membranes was improved considerably with an increase of SPC content while the pure water permeation flux decreased remarkably. Using PEG/PVP mixture instead of PEG as pore-forming agent increased pure water flux of PES/SPC blend membrane to some extent.     

酞侧基聚芳醚砜／对苯二甲酸乙二酯－对羟基苯甲酸嵌段共聚物共混物的研究

酞侧基聚芳醚砜／对苯二甲酸乙二酯－对羟基苯甲酸嵌段共聚物共混物的研究李刚，殷敬华，李滨耀（中国科学院长春应用化学研究所，长春，１３００２２）关键词酞侧基聚芳醚砜，热致性液晶高聚物，原位复合材料，对苯二甲酸乙二酯－对羟基苯甲酸嵌段共聚物将热塑性树脂与热...     

Hydrophilic modification of polyethersulfone membranes by low temperature plasma-induced graft polymerization

A complete and permanent hydrophilic modification of polyethersulfone (PES) membranes is achieved by argon plasma treatment followed by polyacrylic acid (PAA) grafting in vapor phase. Both Ar plasma treatment alone and post-PAA grafting rendered a complete hydrophilicity to the PES membranes. The hydrophilicity of the membranes treated with only the Ar plasmas is not, however, permanent. In contrast, the PES membranes treated with Ar plasma and subsequent acrylic acid (AA) grafting are permanently hydrophilic. High energy resolution X-ray photoelectron spectroscopy (XPS) confirmed the grafting of PAA to all surfaces of the membrane. Furthermore, water bubble point measurements remain unaffected. The pore sizes of the grafted membranes at higher grafting yield are slightly decreased. The modified membranes are less susceptible to protein fouling than the unmodified membranes and the pure water flux for the modified membranes was tremendously increased by plasma treatment. Furthermore, the modified membranes are easier to clean and required little caustic to recover permeation flux.     

酞侧基聚芳醚砜／对苯二甲酸乙二酯－对羟基苯甲酸嵌段共聚物共混物的研究

The blends of phenolphthalein Polyethersulfone (PES - C ) and a thermotropic liquid crystalline polymer (LCP ) were prepared using melting mixing method.Rheological and mechanical properties of the blends were investigated. It was shown that addition of LCP in PES-C resulted in marked reduction of melt viscosity and improved processibility. The Chadly impact strength of the blend containing 2. 5% LCP increased about 2. 5 times comparing with pure PES-C. The tensile strength, Young's modulus, fie-cural strength and flexural modulus of the PES-C/LCP blends were also improved on some extent. The morphology of these blends were also observed by SEM,and the relationship between the me-chanical properties and the morphology of blends were discussed.     

Preparation, morphologies and properties for flat sheet PPESK ultrafiltration membranes

Flat sheet poly(phthalazinone ether sulfone ketone) (PPESK) ultrafiltration membranes were prepared. The effects of PPESK concentration, solvents, additives and exposing time on the structure and performance of PPESK ultrafiltration membranes were investigated in more detail. The optimal preparation conditions were: 12 wt.% PPESK, NMP/DMAc mixed solvent (mass ratio = 1), 8 wt.% polyethylene glycol 400 (PEG400), 2.5 wt.% LiCl and 5 s exposing time. Under these conditions, the pure water flux and the rejection of γ-globulins were 1139L/m² h and 93.7% at the operation pressure of 0.1 MPa, respectively.

Scanning electron microscope (SEM) micrographs showed that spongy structure could be formed while finger-like structure could be suppressed due to the longer exposing time or higher LiCl concentration.     

Amphiphilic PPESK-g-PEG graft copolymers for hydrophilic modification of PPESK microporous membranes

Amphiphilic graft copolymers comprising poly(phthalazinone ether sulfone ketone) (PPESK) backbones and poly(ethylene glycol) (PEG) side chains were synthesized and blended into PPESK casting solutions to prepare hydrophilic and anti-fouling microporous membranes. The graft copolymer was prepared by a modified Williamson etherification method. Sodium alkoxide of methoxyl PEG (PEG-ONa) was used to react with chloromethylated PPESK (CMPPESK). FT-IR spectroscopy, ¹H NMR and solid-state ¹³C CP-MAS NMR analysis confirmed the covalent linking of PEG with PPESK backbones. The incorporation ratio of PEG calculated from ¹H NMR was in agreement with that from TGA tests. The graft products were added into PPESK casting solutions to prepare composite porous membranes using phase inversion method. X-ray photoelectron spectroscopy (XPS) and water contact angle examinations indicated that the grafting copolymers were preferentially excluded to the membrane-coagulant interface during membrane forming, contributing the membranes with improved hydrophilicity and surface wettability. Compared with the neat membrane, the blend membranes exhibited a larger surface pore size and less susceptible to protein fouling.     

Carbohydrates as Additives for the Formation of Isoporous PS‐b‐P4VP Diblock Copolymer Membranes

Highly porous polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer membranes are prepared using carbohydrates as additives. Therefore α‐cyclodextrine, α‐(D )‐glucose, and saccharose (cane sugar) are tested for the membrane formation of three different PS‐b‐P4VP polymers. The addition of the carbohydrates leads to an increasing viscosity of the membrane solutions due to hydrogen bonding between hydroxyl groups of the carbohydrates and pyridine units of the block copolymer. In all cases, the membranes made from solution with carbohydrates have higher porosity, an improved narrow pore distribution on the surface and a higher water flux as membranes made without carbohydrates with the same polymer, solvent ratio, and polymer concentration.     

聚醚砜/纤维素晶体共混膜材料及其超滤性能

聚醚砜与纤维素晶体等共混成铸膜液,采用浸没沉淀相转化法制备聚醚砜/纤维素晶体共混膜材料.通过超滤装置检测复合膜的水通量、截留率、平均孔径、孔隙率、抗污染性等超滤性能,从而讨论了纤维素晶体含量对共混膜超滤性能的影响.采用抗张测试机、热重分析仪(TGA)、原子力显微镜(AFM)对共混膜的力学性能、热稳定性能、形貌结构进行表征.结果表明,随着纤维素晶体的含量的增加,共混膜的纯水通量先升高后有所降低,截留率均保持在91%～95%,抗张强度、断裂伸长率先增大后有所下降,抗污染性较纯聚醚砜膜显著提高.当纤维素晶体质量分数为1%时,纯水通量达到最大为813.3L·m-2·h-1,孔隙率为88.8%,平均孔径达为70.9nm,抗张强度为7.25MPa,断裂伸长率为11.6%,平均污染度FR值为22.0%,衰减系数m值为35.8%.共混膜具有由纤维素晶体、聚醚砜热降解分别引起的两个失重阶段.共混膜为典型非对称膜结构,表皮层较为致密,多孔支撑层孔径较大.     

Influence of membrane structure on fouling layer morphology during apple juice clarification

The flux behavior of 0.2 μm nylon, polysulfone (PS), polyvinylidene fluoride (PVDF) and polyethersulfone (PES) membranes was examined during dead-end microfiltration of commercial apple juice. On nylon membranes, a 0.1 μm thick surface fouling layer rapidly formed that acted as a secondary membrane. The colloidal particles retained by this surface layer aggregated to form a thick loose gel structure, producing an anisotropic fouling structure. In contrast, the 4 μm thick surface fouling layer of PES was slower to form and had a more open structure with a lower flux resistance per unit thickness. The morphology of the PES surface layer also did not differ dramatically from the loose gel structure that subsequently formed on top of this secondary membrane. The PS surface fouling layer was similar in structure to nylon whereas the PVDF layer more closely resembled that found with PES. The density of the surface fouling layer did not directly correlate to membrane surface hydrophobicity or pure water flux. Atomic force microscopy (AFM) indicated that surface roughness strongly influenced surface fouling layer morphology. The membrane surface appears to act as a template for the fouling process; therefore, smooth membranes (nylon and PS) produce a dense surface fouling layer whereas this same layer on rough membranes (PES and PVDF) is much more open. Consequently, the fluxes of PES and PVDF membranes are less affected by fouling formation.     

热致相分离法偏二氯乙烯-氯乙烯共聚物多孔膜的制备及性能

以偏二氯乙烯-氯乙烯共聚物[P(VDC-co-VC)]为成膜聚合物, 邻苯二甲酸二甲酯(DMP)为稀释剂, 采用热致相分离(TIPS)法制备了具有多孔结构的P(VDC-co-VC)膜. 通过聚合物-稀释剂二元体系相图、 场发射扫描电镜(FESEM)、 差示扫描量热仪(DSC)、 X射线衍射(XRD)、 原子力显微镜(AFM)、 纯水通量、 接触角、 孔径及其分布、 截留率及力学性能等研究了聚合物含量对P(VDC-co-VC)多孔膜结构和性能的影响. 结果表明, P(VDC-co-VC)-DMP二元体系成膜过程以液-液(L-L)分相为主, 随着聚合物含量增加, 膜的横截面由类花瓣状结构向胞腔状结构转变, 膜的孔连通性降低, 结构变得较为致密, 同时膜上表面孔隙率降低, 粗糙度增大. L-L分相时间和聚合物含量的变化, 导致膜结晶度先降低后增大. 聚合物含量的增加使膜上表面接触角、 断裂强度及蛋白截留率增加, 但膜的平均孔径、 孔隙率及纯水通量先增加后减小. 当聚合物质量分数为30%时, 所得膜通透性较优, 断裂强度可达7.5 MPa.     

Nanostructured polyethersulfone membranes for dye and protein separation: Exploring antifouling role of holmium (III) molybdate nanosheets

Nanostructured polymer membranes are nowadays of crucial importance in achieving antifouling properties. Nanomaterials with tunable composition, size, and morphology, surface modification and functionality offer unprecedented opportunities for efficient wastewater treatment. In this work, the effect of holmium (III) molybdate (Ho₂MoO₆) nanomaterial as a new nanofiller on preparation of nanostructured polyethersulfone (PES) mixed matrix membranes was examined in terms of hydrophilicity, membrane morphology, permeability, dye and protein separation and antifouling property. The Ho₂MoO₆ nanosheets were synthesized and characterized by FTIR, XRD, and FESEM and used in different amounts in PES matrix. The pore size and the membrane porosity increased with Ho₂MoO₆ loading. The nanocomposite membranes showed enhancement in hydrophilicity, antifouling properties, dye rejection and permeability. The remarkably pure water flux (195 L/m²h at 3 bar) and 92.3% flux recovery after bovine serum albumin (BSA) filtration were obtained for the membrane mixed with 2 wt% Ho₂MoO₆ compared to 95 L/m²h and 75.2% obtained for the bare PES, respectively. Moreover, significantly high rejection of Acid Red 125 (95 ± 1%) was achieved. Thus, the experimental results established the potential efficiency of the novel nanocomposite membrane for the separation applications.     

Development of a new styrene copolymer membrane for recycling of polyester fibre dyeing effluent

A new ultra-filtration membrane has been developed using indigenously available polymer, low cost solvents and a simple casting technique. The performance evaluation of the developed membrane in terms of pure water permeability (PWP), flux and rejection as compared to commercially available national and international membranes was carried out. It is observed that the newly developed membranes show acceptable performance both in terms of flux and rejection. The compressibility characteristic of the new membrane shows an improvement after suitable chemical modification through cross-linking reactions. The application perspectives of the membranes developed in our laboratory have been evaluated for the selective separation of dyes from typical textile waste stream of polyester fibre dyeing units with an aim to recover and recirculate the auxiliary chemicals and water in the process house. The rejection of dyes >98% and the permeate flux (0.8–1.0 m³/m² per day) values obtained for a specific type of textile effluent is of acceptable standards.The membranes were characterised for pore size and pore size distribution using molecular weight cut-off, combined bubble pressure and solvent permeability method. Membrane morphology has been studied using scanning electron microscopy (SEM). The other features of the developed membrane are its resistance to temperature and adverse chemical environment.