聚偏氟乙烯微孔膜制备方法研究进展

介绍了浸没沉淀法、热致相分离法以及蒸发助热致相分离法制备聚偏氟乙烯(PVDF)微孔膜的研究进展.重点介绍了溶剂、凝固浴组成、凝固浴温度、添加剂和蒸发时间等因素对浸没沉淀法制备PVDF膜的影响,并对制备PVDF膜的发展提出建议和展望.同时简单介绍了PVDF微孔膜的亲水性改性.     

增强型聚偏氟乙烯微孔膜的研制

通过相转化法制备无纺布支撑的增强型聚偏氟乙烯微孔膜,确定二甲基乙酰胺(DMAC)为溶剂,氯化锂为第二添加剂,以水作为凝胶浴.研究了添加剂组成和浓度、凝胶浴组成和浓度、凝胶浴温度、热处理条件等因素对聚偏氟乙烯膜性能的影响.     

混合溶剂对TiO2/PVDF平板超滤膜性能和结构的影响

采用N,N-二甲基乙酰胺(DMAC)和N-甲基吡咯烷酮(NMP)为混合溶剂制备PVDF超滤膜。考察了不同混合比例的DMAC和NMP对膜性能及膜结构的影响,同时利用扫描电子显微镜(SEM)对膜表面及断面结构进行分析,原子力学显微镜(AFM)对膜表面粗糙度进行了分析,利用接触角测量仪对膜表面接触角进行了测量。结果表明,使用混合溶剂对膜孔径和膜亚层结构影响较大,但混合溶剂对膜孔隙率和接触角基本没有影响。当混合溶剂DMAC/NMP为1:2时,膜性能达到最优,孔隙率为70%,平均孔径为0.24μm,水通量为373 L.m-2.h-1,截留率为88%。     

聚偏氟乙烯管式微孔膜的工艺研究

对聚偏氟乙烯(PVDF)管式微孔膜生产工艺进行了研究。系统地讨论了相转化法制备管式微孔膜过程中各个因素的影响。研究发现,铸膜液温度对PVDF管式膜截留率和纯水通量影响不明显;铸膜液中加入NH4Cl后,膜的纯水通量增加,截留率减小,孔径增大;不同凝固浴制得的PVDF管式微孔膜不同,膜的纯水通量和截留率也不同。     

Preparation of PVDF hollow‐fiber membranes via immersion precipitation

Porous polyvinylidene fluoride (PVDF) hollow‐fiber membranes with high porosity were fabricated using the immersion precipitation method. Dimethylacetamide (DMAc) and N‐methyl‐2‐pyrrolidone (NMP) were used as solvent, respectively. In addition, polyvinylpyrrolidone (PVP), lithium chloride, and organic acids were employed as nonsolvent additives. The effects of the internal and external coagulation mediums on the resulting membrane properties were also investigated. The resulting hollow‐fiber membranes were characterized in terms of maximum pore radius, mean pore radius, effective surface porosity as well as wetting pressure. The structures of the prepared hollow fibers were examined using a scanning electron microscope. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1643–1653, 2001     

Preparation and characterization of metal-complex imprinted PVDF hollow fiber membranes

Using nickel-2,2′-dipyridyl complex as a template, N-vinyl-2-pyrrolidone as the metal coordination functional monomer, and ethylene glycol dimethacrylate as the crosslinker, polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration membrane as the supported membrane, metal complex imprinted polymeric membranes were prepared. The association constant of template-monomer interaction in the prepolymerization solution was estimated to be 4.38 × 10⁴ (L/mol)² by spectrophotometric titration analysis. The attenuated total reflection Fourier transform infrared spectroscopy and scanning electron micrograph characterization indicated that the surface of the support PVDF membrane was completely coated by the imprinted polymer layer after modification. The imprinted membranes exhibited the selective permeability for the template in certain nickel acetate solution. The molecularly imprinted membranes gave higher permeation separation factors at about pH 6, whereas increasing pressure would lower the separation ability. The effects of ion concentration, cations and counterions, ligand selectivity, pH, and trans-membrane pressure were investigated and the permeation performances of the imprinted membranes could be regarded as facilitated transport mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

超疏水聚偏氟乙烯复合微孔膜的制备及性能

提出了一种超疏水聚偏氟乙烯（PVDF）复合微孔膜的制备方法。以相转化法制备的PVDF膜为基膜,通过恒压过滤将多壁碳纳米管（MWCNTs）沉积到PVDF基膜表面,再经聚二甲基硅氧烷（PDMS）溶液修饰,可制得接触角达162°、滚动角约10°的PVDF复合微孔膜。用原子力显微镜和扫描电镜对膜表面进行结构分析,并测试了膜的接触角、气通量和机械强度等性能,考察了MWCNTs及PDMS浓度对膜结构和性能的影响。研究表明,CNTs在具有微米级粗糙度的基膜上强化了纳米结构,提高了膜的粗糙度,PDMS降低了膜的表面能,二者协同作用使复合膜的接触角大幅提高,滚动角显著下降。与高度疏水的PVDF基膜相比,PVDF复合膜的疏水性大幅提高,断裂伸长率加倍,在模拟海水真空膜蒸馏过程中,保持了较高的传质通量和截留率,具有更好的操作稳定性和抗污染性能。     

Preparation of microporous PVDF membrane via tips method using binary diluent of DPK and PG

Microporous polyvinylidene fluoride (PVDF) membrane was prepared via thermally induced phase separation (TIPS) method using a binary diluent of diphenyl ketone (DPK) and 1,2‐propylene glycol (PG). The phase diagram for the PVDF/binary diluent of DPK and PG system was measured in the range of the PG/DPK mass ratio changing from 0 to 2/3. Then the effects of the PG/DPK mass ratio and the PVDF concentration on membrane cross‐section structures and tensile strength were also investigated. The results showed that the addition of PG brought about a shift of the cloud point curve to a higher temperature and the extension of the liquid–liquid phase separation region to a higher polymer concentration. Therefore a bicontinuous cross‐section structure was obtained when the PG/DPK mass ratio was 3/7 and the polymer concentration was 30 wt %. As an increase of the PG/DPK mass ratio, the tensile strength increased gradually at a fixed PVDF concentration. Moreover, for the same PG/DPK mass ratio, the cross‐section microstructure changed from a bicontinuous or a cellular structure to a spherulitic structure, and the tensile strength increased drastically as the polymer concentration increased from 20 to 50 wt %. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of antibacterial polyvinylidene fluoride (PVDF) ultrafiltration membranes with direct addition of N-halamine polymers

In this study, novel antibacterial ultrafiltration polyvinylidene fluoride (PVDF) flat sheet membranes were produced with addition of synthesized N-halamine polymers. The ternary phase diagrams of PVDF and the synthesized polymers with N-methyl-2-pyrrolidone and water systems were prepared. The water flux and BSA rejection performances of the produced membranes were assessed both with and without PVP addition, and compared with a commercial membrane. The produced membranes were characterized with FTIR, XPS, DSC, and SEM analysis. Addition of N-halamine polymers to the membrane structure significantly improved the biocidal performance of the produced membranes against Staphylococcus aureus and Escherichia coli (10⁵ CFU).     

氧化铝凝胶改性聚偏氟乙烯超滤膜的制备与表征

为提高聚偏氟乙烯超滤膜的亲水性,采用Al_2O_3凝胶对有机高分子聚偏氟乙烯膜进行改性,制备Al_2O_3凝胶改性聚偏氟乙烯超滤膜,并与非凝胶化无机纳米Al_2O_3颗粒改性进行对比。考察铸膜液中Al_2O_3凝胶加入量对改性聚偏氟乙烯超滤膜性能和结构的影响。采用扫描电镜、X射线能谱、傅里叶红外光谱和超滤实验等对超滤膜结构和性能进行表征,结果表明,Al_2O_3凝胶加入量1.0 g时,改性超滤膜水通量提高5.48倍;扫描电镜表明,改性超滤膜和未改性超滤膜均为典型的非对称结构,改性超滤膜表面孔数目明显增加,断面微观结构未发生改变;红外光谱及能谱分析表明,Al_2O_3凝胶与高分子聚偏氟乙烯之间为物理共混。Al_2O_3凝胶改性聚偏氟乙烯超滤膜,改善了膜表面亲水性,提高水通量,并保持较大截留率。     

Preparation and characterization of PVDF-PFSA flat sheet ultrafiltration membranes

High performance polyvinylidene fluoride (PVDF) flat sheet ultrafiltration (UF) membranes have been prepared by an immersion precipitation phase inversion method using perfluorosulfonic acid (PFSA) as a pore former and as a hydrophilic component of the membranes and polyethylene glycol (M_w = 400) (PEG400) as a pore forming agent. The effects of the presence of PEG and the concentration of the PFSA on the phase separation of the casting solutions and on the morphologies and performance of UF membranes including their porosity, water flux, rejection of bovine serum albumin (BSA) protein, and anti-fouling property were investigated. Phase diagrams, viscosities and the phase separations upon exposure to water vapor showed that both PEG400 and PFSA promoted demixing of the casting solution. Scanning electron microscopy measurements showed that the PVDF-PFSA blend membranes had more macropores and finger-like structures than the native PVDF membranes. The PVDF-PFSA membrane (5 wt-% PEG400+ 5 wt-% PFSA) had a pure water flux of 141.7 L/m²·h, a BSA rejection of 90.1% and a relative pure water flux reduction (RFR) of 15.28%. These properties were greatly superior to those of the native PVDF membrane (pure water flux of 5.6 L/m²·h, BSA rejection of 96.3% and RFR of 42.86%).     

In‐situ cross‐linked PVDF membranes with enhanced mechanical durability for vacuum membrane distillation

A novel and effective one‐step method has been demonstrated to fabricate cross‐linked polyvinylidene fluoride (PVDF) membranes with better mechanical properties and flux for seawater desalination via vacuum membrane distillation (VMD). This method involves the addition of two functional nonsolvent additives; namely, water and ethylenediamine (EDA), into the polymer casting solution. The former acts as a pore forming agent, while the latter performs as a cross‐linking inducer. The incorporation of water tends to increase membrane flux via increasing porosity and pore size but sacrifices membrane mechanical properties. Conversely, the presence of EDA enhances membrane mechanical properties through in‐situ cross‐linking reaction. Therefore, by synergistically combining the effects of both functional additives, the resultant PVDF membranes have shown good MD performance and mechanical properties simultaneously. The parameters that affect the cross‐link reaction and membrane mechanical properties such as reaction duration and EDA concentration have been systematically studied. The membranes cast from an optimal reaction condition comprising 0.8 wt % EDA and 3‐hour reaction not only shows a 40% enhancement in membrane Young's Modulus compared to the one without EDA but also achieves a good VMD flux of 43.6 L/m²‐h at 60°C. This study may open up a totally new approach to design next‐generation high performance MD membranes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4013–4022, 2016     

非良溶剂存在下静电纺PVDF和P(VDF-HFP)纤维的可纺性研究

将聚偏氟乙烯(PVDF)和聚偏氢氟乙烯-六氟丙烯共聚物[P(VDF-HFP)]分别溶解于良溶剂N,N-二甲基乙酰胺(DMAc)和非良溶剂丙酮(Act)的混合体系中(DMAc:Act体积比为3:7),用静电纺丝法制备两种超细纤维。考察了在非良溶剂存在的情况下两种溶液浓度和增比粘度(η8p)的依赖关系,测定了两种溶液中的缠结浓度(Ce)。结果表明,PVDF和[P(VDF-HFP)]两种溶液的浓度的对数和8p的对数在一定的浓度范围内存在线性关系,其Ce的质量分数分别为6．8％和4．8％;静电纺纤维经扫描显微镜观察表明,在缠结数评估失效情况下,Ce对两种含非良溶剂的高聚物溶液可纺性也具有半定量的评估作用。两种溶液浓度低于Ce时无法纺出纤维,主要形成聚合物液滴;Ce是电纺出珠状纤维的最小浓度,而纺出均一的无珠纤维溶液浓度为(2-2．5)Ce。     

聚乙烯阴离子交换膜掺混聚偏氟乙烯改性表征

聚偏氟乙烯（PVDF）因含氟乙烯基单体,拥有良好的化学稳定性、热学稳定性和机械性能,与其他高分子膜材料相比更容易提高离子交换膜的性能。本实验采用热压法制备PVDF聚乙烯阴离子交换膜,探讨了PVDF含量对膜性能的影响,如膜电阻、离子交换容量、耐破度、含水率和选择透过性。利用红外光谱仪及扫描电子显微镜表征手段对PVDF膜表面性质和结构进行了分析。结果表明,当PVDF含量增加时,膜面电阻、耐破度升高。离子交换容量、含水率,反离子选择透过性降低。虽然PVDF的添加导致含水率、交换容量等膜性能的下降,但耐破度的升高表明膜稳定性和机械性能得到了提升,这赋予PVDF聚乙烯膜一定的使用价值。     

Photocatalytic and antimicrobial efficacy of PVDF/TiO2 membranes fabricated by solution blow spinning

With its ability to purify water and treat wastewater, photocatalytic membranes have become a promising solution. The membrane's unique properties allow for the separation of solid compounds and the degradation of organic materials through photocatalytic and antibacterial means. Poly(vinylidene fluoride)/titanium oxide (PVDF/TiO₂) composite remain the materials of choice for making these membranes due to their economy, effectiveness, safety, and durability. In this work a photocatalytic membrane reactor (PMR) system was developed using PVDF/TiO₂ membranes fabricated by the solution blow spinning (SBS) process. Obtaining photocatalytic membranes using this method is an efficient and ecological route that overcomes the disadvantage of separating the photocatalyst after the treatment is complete. The results of PMR system showed that the PVDF/TiO₂ membrane could effectively remove total coliforms and E. coli from polluted water. After 10 min of contaminated water circulation through the PMR system, the presence of pathogens was not detected, indicating the efficiency of the obtained membranes.     

聚偏氟乙烯/纳米纤维素复合超滤膜的研究

以聚偏氟乙烯为原材料,聚乙烯吡咯烷酮( PVP K30)为添加剂,并向聚偏氟乙烯铸膜液中混入纳米纤维素,采用相转化工艺制备了复合超滤膜.通过正交试验分析了各因素对产品性能的影响,并得出了制备复合超滤膜的最优条件:聚偏氟乙烯质量分数为14％,添加剂PVP K30质量分数为0.5％,纳米纤维素加入量为0.7％,空气中溶剂蒸发时间为10s,凝胶浴为水.测定复合超滤膜的水通量、截留率、平均孔径、孔隙率、力学强度等一系列性能,膜的水通量为40.7 L/(m2·h),对牛血清蛋白的截留率为91.8％,孔隙率为52.3％,平均孔径为15.3 nm.     

聚偏氟乙烯微孔膜的制备与透过性能研究

采用相转化法制备聚偏氟乙烯（PVDF）微孔膜,研究了铸膜液中聚偏氟乙烯含量、溶剂的种类、添加剂的种类和含量、膜厚度以及操作压力等因素对聚偏氟乙烯膜水通量的影响,采用扫描电子显微镜观测了制备膜的表面结构。结果表明,制膜条件对聚偏氟乙烯微孔膜通量有重要影响,通量随添加剂含量和压力的增大而增大,随PVDF含量和膜厚度的增大而减小;当压力上升到0．16MPa时,通量将不随压力变化,达到极限通量。     

溶胀辊轧法PVDF膜表面的疏水强化：溶胀剂的影响

提出了一种简便、低成本的聚偏氟乙烯（PVDF）微孔膜表面疏水增强方法——溶胀辊轧法,以微结构辊筒对表面喷涂溶胀剂的PVDF成品微孔膜辊轧后,采用浸没凝胶法成膜。以N-甲基吡咯烷酮/水（非溶剂）为溶胀体系,采用扫描电子显微镜（SEM）、原子力显微镜（AFM）、水接触角（WCA）、最大孔径、平均孔径、N₂通量、耐磨性、液体穿透压（LEP）等表征手段,系统地研究了溶胀剂体系、溶胀剂容量对PVDF微孔膜结构与性能的影响。结果表明：辊轧膜表面呈现微米-亚微米层次特征,溶胀辊轧操作起到了疏水增强、透过能力提升的效果。溶胀剂中水（非溶剂）质量分数为6%、喷涂密度为0.03mL/cm²时,膜性能最优。连续运行30h的真空膜蒸馏（VMD）对比实验表明,辊轧膜较未辊轧膜具有更高的产水通量、脱盐率及更好的耐污染性能。该方法为低成本、连续化进行成品膜表面疏水强化提供了一种新选择。     

超临界CO2诱导相分离法制备石墨烯改性PVDF膜的研究

以聚偏氟乙烯（PVDF）为基体,N,N二甲基甲酰胺（DMF）为溶剂,通过超临界CO2诱导相转化法制备PVDF/石墨烯微孔膜,并对其微观形貌、热稳定性能、热力学性能、晶型转化和亲水性能等进行表征。结果表明,在8 MPa,45 ℃的制备条件下,低含量石墨烯掺杂比可以制备得到良好网络结构的PVDF微孔膜,孔径和粗糙度均有所降低,亲水性能提高,整体热稳定性提高;石墨烯添加对微孔膜热力学性能的影响较小,但增强了PVDF晶型转换,趋向于形成更多的β或γ晶型。