亲疏水性CuBTC/PVDF复合膜应用于膜蒸馏抗油实验

采用水热法合成亲水性的CuBTC金属有机骨架(MOFs)颗粒,采用聚乙烯醇(PVA)作为黏合剂,用抽滤的方法将CuBTC颗粒附载在聚偏氟乙烯(PVDF)膜上,之后用戊二醛(GA)对PVA进行交联,制备出表层亲水、底层疏水的CuBTC/PVDF复合膜。通过场发射电子显微镜、比表面积及孔径分析仪、接触角测量仪、孔径分析仪、X射线衍射仪等对CuBTC颗粒和不同CuBTC含量的复合膜的表面特征、结构形态和稳定性进行了表征。结果表明,CuBTC颗粒有着较大的比表面积和孔容,CuBTC颗粒可以牢固地抽滤在PVDF膜表面,热稳定性高且有较好的柔韧性。与抽滤前的PVDF膜相比,随着CuBTC颗粒的增多,膜厚度有所增加,孔径和孔隙率有所减小,但对其膜蒸馏膜通量的影响不大,且在CuBTC含量在0.6 g时表现出较好的性能。在以1 g/L原油和35 g/L氯化钠混合溶液为进料液对原膜和复合膜进行直接接触膜蒸馏抗油污实验,发现原膜很快被油污染堵塞毛孔,而复合膜具有良好的抗油污染能力,可以进行长期的膜蒸馏实验。     

Preparation of PET threads reinforced PVDF hollow fiber membrane

PET threads were incorporated in the support layer of hollow fiber membrane in axial direction as a special reinforcement material for the purpose of improving the mechanical properties of PVDF hollow fiber membranes. It was found that the reinforcement threads had a limited effect on the separation-related properties of the membrane, such as porosity and pore size, but the tensile strength of the reinforced membrane was improved several folds. Also, the criterion of choosing reinforced fiber materials was suggested.     

Solution‐derived ferroelectric vinylidene fluoride oligomer thin films with large polarization

Dense and uniform vinylidene fluoride (VDF) oligomer thin films with a highly polar β phase were prepared for the first time by a low‐cost and scalable solution casting approach, after treatments of substrate surface functionalization and hot‐pressing. Introducing hydrated salt in the precursor solution effectively promoted the ferroelectric β phase. The VDF oligomer thin films obtained with short molecular chains exhibited high crystallinity and high remnant polarization (91 mC m^?2), which is larger than both the polymer and copolymer counterpart films. The reasons for the observed low dielectric constant at low electric field, despite its larger polarization at high field, and the relatively high coercive field are discussed on the basis of the distinct structural characteristics of VDF oligomers. The low polar bulky end‐groups and difficulties in kink formation and propagation may result in the observed low dielectric constant at low electric field and the high coercive field. Copyright © 2011 Society of Chemical Industry     

Compatibility of poly(vinylidene fluoride) (PVDF)/polyamide 12 (PA12) blends

Poly(vinylidene fluoride) (PVDF)/polyamide 12 (PA12) blends showed new peaks in XRD profile with increasing PA12 and the crystallinity of PA12 significantly decreased with the addition of PVDF. PVDF showed three relaxation regions at about −40, 40, and 100°C, respectively, and glass transition temperature (T_g ) of PA12 increased in blends (10.8→30.14°C) and α‐relaxation of PVDF decreased from 100.26 to 86.46°C. Complex viscosities (η*) vs. composition curve showed a great positive deviation in PVDF‐rich and a small negative deviation in PA12‐rich blends. The N—H and C=O stretching band of PA12 shifted slightly toward higher wavelength, and from curve‐fitted data the area of hydrogen‐bonded C=O stretching bands of PA12 decreased with the addition of PVDF, especially in the 30/70 blend, implying the existence of interactions between the β‐hydrogen atom of PVDF and amide carbonyl group of PA12 in the blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1374–1380, 2000     

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     

强疏水性PDMS/PVDF微孔膜的制备及其性能研究

利用非溶剂相转化法（NIPS）,通过在聚偏氟乙烯(PVDF)铸膜液中加入聚二甲基硅氧烷(PDMS),制备了PDMS/PVDF共混疏水微孔膜,并研究了凝胶浴组成（水/乙醇）对铸膜液凝胶动力学、膜形貌、疏水性及力学性能的影响。结果表明,随着凝胶浴中乙醇百分含量由零增加至100 %时,PDMS/PVDF共混膜的断面上指状孔基本消失,海绵状孔结构贯穿断面;当凝胶浴中乙醇含量为100 %时,PDMS与PVDF发生分相;膜表面疏水性能增加,水接触角达到139.68 °;弹性模量、拉伸强度、断裂伸长率分别由（48.06±4.20）、（2.82±0.15） MPa、（92.90±2.53） %下降至（15.70±2.83）、（0.72±0.13） MPa、（15.47±1.63） %。     

Formation of an interconnected lamellar structure in PVDF membranes with nanoparticles addition via solid‐liquid thermally induced phase separation

Novel microporous membranes were prepared via thermally induced solid‐liquid (S‐L) phase separation of mixtures containing poly(vinylidene fluoride) (PVDF)/diphenyl ketone (DPK)/nanoparticles [such as montmorillonite (MMT) and polytetrafluoroethylene (PTFE)] in diluted systems with a mass ratio of 29.7/70/0.3 wt %. The crystallization and melting characteristics of these diluted systems were investigated by polarizing optical microscopy (POM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and wide angle X‐ray diffraction (WAXD). The nanoparticle structure and the interaction between PVDF chains and nanoparticle surfaces determined the crystallization behavior and morphology of the PVDF membrane. The addition of MMT and PTFE had a significant nucleation enhancement on the crystallization of PVDF accompanied by S‐L phase separation during the thermally induced phase separation (TIPS) process. It was observed that an interconnected lamellar structure was formed in these two membranes, leading to a higher tensile strength compared with that of the reference membrane without nanoparticles addition. Additionally, addition of MMT facilitates the fiber‐like β phase crystal formation, resulting in the highest elongation at break. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Gold‐Nanoparticle‐ and Gold‐Nanoshell‐Induced Polymorphism in Poly(vinylidene fluoride)

PVDF nanocomposites are prepared through solution mixing of Au‐NPs or Au‐NSs with PVDF. The novel optical properties of Au‐NPs and ‐NSs are retained as confirmed from UV‐Vis spectra. Analysis of resulting nanocomposites by FT‐IR, XRD, and DSC shows an obvious polymorphism change from α‐ to β‐form compared to PVDF prepared under the same conditions. The β‐polymorph seems to be more prominent with higher concentration of Au‐NPs (0.5%) and even more so with Au‐NSs. Thermogravimetric analysis shows that both nanocomposites have better resistance toward thermal degradation. Combination of novel optical properties of Au‐NPs or Au‐NSs with induced ferroelectric‐active β‐polymorph in PVDF can lead to new design of optical, piezoelectric devices.

     

Thermal conductivity of PVDF/PANI-nanofiber composite membrane aligned in an electric field

Poly(vinylidene fluoride)(PVDF) is a semi-crystalline thermoplastic polymer with excellent thermal stability,electrochemical stability and corrosion resistance, which has been widely studied and applied in industrial nonmetallic heat exchanger and piezoelectric-film sensor. In this study, polyaniline(PANI) nanofibers were synthesized using dodecylbenzene sulfonic acid as the surfactant. The obtained PANI nanofibers were blended in PVDF matrix to enhance thermal conductivity and tensile strength of composite materials. Electric field was applied for the orientation of membrane structure during membrane formation. Scanning electron microscope(SEM) images exhibited that the PANI nanofibers were well-dispersed in the composite membranes. The structure of composite membranes was more orderly after alignment. X-ray diffraction(XRD) and differential scanning calorimetry(DSC) indicated that the content of PANI nanofibers contributed to the transformation of PVDF from α-phase to β-phase. Both the tensile strength and thermal conductivity of composite membranes were significantly improved. This tendency was further enhanced by the application of electric field. The maximum tensile strength was obtained when the content of PANI nanofibers was 3 wt%, which was 46.44% higher than that of pure PVDF membrane. The maximum thermal conductivity of composite membranes after alignment was 84.5% greater than that of pure PVDF membrane when the content of PANI nanofibers was 50 wt%. The composite membrane is a promising new potential material in heat transfer field and the mechanism explored in this study would be informative for further development of similar thermal conductive polymeric materials.     

Sulfonated polyether sulfone‐poly(vinylidene fluoride) blend membrane for DMFC applications

Direct methanol fuel cell (DMFC) proton exchange membranes were prepared by blending poly (vinylidene fluoride) (PVDF) with sulfonated poly(ether sulfone) (SPES). Using a diffusion cell and gas chromatographic technique, the effects of PVDF content on methanol permeability in the blended membranes were investigated. The thermal resistance and proton conductivity of the membranes were also determined by using a thermal gravimetric analysis (TGA) and an impedance analysis technique respectively. The presence of sulfonic acid groups in SPES was confirmed by Fourier transform infrared (FTIR). It was found that the methanol permeability in the blended membranes decreased with PVDF content at the expense of proton conductivity. Blended membranes show methanol permeability values much lower than that of Nafion 115, whereas the proton conductivities of the membranes are comparable with that of Nafion. The thermal stability of these blended membranes is above 250°C, which is sufficiently high for use in DMFC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

基于PVDF薄膜辐照接枝制备质子交换膜

含氟磺酸型质子交换膜是一类具有高热稳定性、化学稳定性及良好力学性能的离子交换膜,具有极其广阔的应用前景。采用⁶⁰Co辐照接枝技术,在聚偏氟乙烯（PVDF）基膜上产生自由基聚合位点,进而接枝对苯乙烯磺酰氯单体,经过一定条件酸碱处理得到一种新型偏氟磺酸型质子交换膜。并对其进行红外分析,结果显示PVDF膜上成功接枝上了对苯乙烯磺酰氯单体;定量研究了在相同辐照总剂量、不同剂量率条件下,所得质子交换膜的质子传导率、吸水率及离子交换容量与接枝率的关系,结果表明：当剂量率为40 Gy·min^-1时,所得质子交换膜接枝率为52.7%,吸水率为36.85%,80℃时质子传导率达到136 mS·cm^-1,离子交换容量为1.274 mmol·g^-1。     

In situ crosslinking of hyperbranched polyglycerol in casting solutions and its effect on the structure and properties of porous PVDF membranes

Porous membranes were prepared via phase inversion process from casting solutions composed of poly(vinylidene fluoride), hyperbranched polyglycerol (HPG), and N,N‐dimethylacetamide. To seek a stable presence of HPG in the resulting membranes, it was crosslinked in the casting solutions using 4,4′‐oxydiphthalic anhydride as the crosslinking agent. The membranes were characterized in terms of morphology, surface and bulk chemical compositions, water contact angle, porosity, water flux, and bovine serum albumin (BSA) adsorption experiments. The effects of HPG content and crosslinking degree on the membrane structure and properties were investigated. The increasing of crosslinking degree resulted in a significant improvement in HPG stability in the membrane matrix, and a remarkable enrichment of the crosslinked HPG at the separation surface was observed when the membrane was shaken in water at a relatively high temperature (60°C). This enrichment led to a decrease in the value of water contact angle and an improvement in fouling‐resistance. To optimize the membrane performance, a small amount of poly(vinylpyrrolidone) (PVP) was used as an additive, and it was found that the addition of PVP led to a considerable increase in water flux. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

“Smart” membrane materials: Preparation and characterization of PVDF‐g‐PNIPAAm graft copolymer

In this research, a smart membrane material of graft copolymer of poly(vinylidene fluoride) with poly(N‐isopropylacrylamide) (PVDF‐g‐PNIPAAm) was synthesized by atom transfer radical polymerization (ATRP) using poly(vinylidene fluoride) (PVDF) as a macroinitiator and direct initiation of the secondary fluorinated site PVDF facilitates grafting the N‐isopropylacrylamide comonomer. The copolymers were characterized by Fourier transform infrared (FTIR), ¹H NMR, gel‐permeation chromatography (GPC), and X‐ray photoelectron spectroscopy (XPS). The temperature‐sensitive membrane was prepared from the PVDF‐g‐PNIPAAm graft copolymers by the phase inversion method. The effects of temperature on the flux of pure water of membrane was investigated. The results showed that alkyl fluorides were successfully applied as ATRP initiators in the synthetic condition and the flux of pure water through the PVDF‐g‐PNIPAAm membrane depended on the temperature change. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1482–1486, 2007     

Structural modifications in stretch-induced crystallization in PVDF films as measured by small-angle X-ray scattering

The nanostructure of stretched and nonstretched PVDF samples was studied by small-angle X-ray scattering (SAXS). The crystallinity of the samples was determined by wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC), and crystalline phases by Fourier transform infrared spectroscopy (FTIR). The nanostructure can be described by a lamellar stacking of crystalline and amorphous layers, with a fairly well defined long period D and a diffuse-boundary in the interface between the crystalline and amorphous phases. The crystallinity of the stretched sample was found to be greater than that of the nonstretched sample. The long period D and the thicknesses of the crystalline lamellae T_c were found to be greater in the stretched sample than those in the nonstretched sample. The thickness of the diffuse-boundary was evaluated as being ∼ 1.4 nm in the nonstretched sample and 1.1 nm in the stretched sample. It was concluded that the growth of the thickness of the crystalline layer induced by the stretching process (stretch-induced crystallization) occurs partially at expense of the diffuse boundary and also by the coarsening of the structure with the stretching process, because of the diminution in the surface area to volume ratio observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Self-standing piezoelectric nanogenerator fabrics from ZnO-doped PVDF nanofiber yarns

Today a wide variety of wearable electronics are in our daily lives and their uses are increasing. The development of portable, flexible, lightweight, cost-effective, and stable devices that produce sustainable energy with renewable approaches in the field of wearable electronics, as in every field, is one of the important issues of today. According to their volume and weight, the use of nanofibers with high surface area in energy-generating devices may bring them advantages such as lightness and higher energy density. Therefore, in recent years, researchers have focused on the development of nanofiber-based nanogenerators that produce energy using mechanical energy in a sustainable and renewable way. In this paper, self-standing piezoelectric nanogenerator (PENG) fabrics were obtained by developing flexible composite poly(vinylidene fluoride) (PVDF) nanofiber yarns doped with zinc oxide (ZnO) nanoparticles at different rates to provide higher power output. It has been characterized from electromechanical, structural, and morphological aspects. The most successful self-standing PENG fabric obtained (at 5% ZnO loading) doubled the energy output of the fabric made from pure PVDF nanofiber yarn and provided a peak total power of 81 μW and a power density of 30 μW/cm². The present results open up the field for the development of PVDF/ZnO-based nanomats and their use in sensors and actuators in the healthcare and engineering industries.     

纳米TiO2复配添加剂对PVDF中空纤维膜结构和性能的影响

该文将纳米二氧化钛（TiO2）粒子与高分子致孔剂、非溶剂、表面活性剂和无机盐4类制膜添加剂复配处理,采用浸没沉淀相转化法制备聚偏氟乙烯（PVDF）-TiO2复合中空纤维膜。通过扫描电子显微镜、X射线衍射、能谱、拉伸试验、接触角测定和截留试验分别对复合膜的微观孔结构、晶相结构、Ti元素分布、机械性能、亲水性、过滤性能和抗污染性能进行了表征,讨论了纳米TiO2粒子对PVDF膜结构和性能的影响。结果表明通过改变复配添加剂中TiO2粒子的含量,可以有效调控复合膜的结构和性能。当复配添加剂中w（TiO2）为2％（占PVDF固含量的质量分数埘％）时,纯水通量由216L／m^2·h提高至402L／m^2·h,牛血清蛋白截留率由95％降低至90％,复合膜整体性能较为优异。     

Fouling reduction of a poly(ether sulfone) hollow‐fiber membrane with a hydrophilic surfactant prepared via non‐solvent‐induced phase separation

Membrane fouling is still a crucial problem, especially in applications for water treatment. When fouling takes place on membrane surfaces, it causes flux decline, leading to an increase in production cost due to increased energy demand. The selection of the right membrane material and a special treatment of the membrane are required to avoid membrane fouling. This article reports the fouling resistance of a poly(ether sulfone) (PES) hollow‐fiber membrane modified with hydrophilic surfactant Tetronic 1307. Experiments on several methods of fouling were carried out to investigate the effect of the addition of nonionic surfactant Tetronic 1307 on membrane fouling. The effectiveness of a chemical agent [sodium hypochlorite (NaClO)] in the reduction of bovine serum albumin (BSA) deposition on the membrane surface was also evaluated. Permeation results showed that the fouling of a PES blend membrane with Tetronic 1307 was lower than that of the original PES membrane in the case of BSA filtration. A treatment with a 100 ppm NaClO solution was capable of removing BSA cake formation and effective at improving the relative permeability. The permeability of a PES blend membrane with Tetronic 1307 was almost 2 times higher than the original permeability when the membrane was treated with a 100 ppm NaClO solution because both BSA and Tetronic 1307 could be decomposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

膜蒸馏用PDMS/PVDF/PTFE三元共混微孔膜制备

采用浸没沉淀相转化法制备了聚二甲基硅氧烷/聚偏氟乙烯/聚四氟乙烯（PDMS/PVDF/PTFE）三元共混微孔膜,并用于20 g/L NaCl水溶液的膜蒸馏脱盐实验。通过扫描电子显微镜观察以及接触角、膜孔隙率和膜平均孔径分析,研究了PTFE含量对膜结构与性能的影响。结果表明,随着PTFE含量的增加,共混微孔膜断面的指状孔逐渐被海绵状取代,平均孔半径由0.234 μm增加到0.354 μm,膜孔隙率由53.4 %增加到81.3 %;膜下表面与水接触角从118.52 °增加到131.11 °;膜蒸馏过程中通量逐渐增加,截留率先稳定后降低,PTFE含量为40 %（质量分数,下同） 时达最大,为99.99 %,此时膜蒸馏通量达16.60 kg/(m2·h)。     

Novel hollow‐fiber anion‐exchange hybrid membranes: Preparation and characterization

To develop ion‐exchange membranes for application in severe conditions, such as those with high temperatures, strongly oxidizing environments, or organic solvents, new hollow‐fiber anion‐exchange hybrid membranes were prepared by the immersion of brominated poly(2,6‐dimethyl‐1,4‐phenylene oxide) base hollow fibers in a tetraethoxysilane–ethanol solution followed by sol–gel and quaternary amination. Compared to conventional polymeric charged membranes, the prepared hybrid membranes were higher in both thermal and dimensional stabilities. The results suggest that tetraethoxysilane concentration was an important factor affecting the membrane's intrinsic properties. When the tetraethoxysilane concentration was in the range 15–45%, the final hollow‐fiber anion‐exchange hybrid membranes had an ion‐exchange capacity of 1.9–2.0 mmol/g, a water uptake of.83–1.23 g of water/g of dry weight, and a dimensional change ratio of 13–18%. An evaluation on the membranes' separation performances is underway. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009