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1.
The importance of poly(vinylidene fluoride) (PVDF) as a membrane material has long been recognised in many membrane processes. Compared to other types of polymeric membranes, the PVDF membranes have received great attention because of its outstanding properties including high hydrophobicity, thermal stability, chemical resistance and excellent mechanical strength. This article provides an overview of recent development in PVDF membrane processes, focussing on the commercial PVDF membrane products for water and wastewater treatment and possible applications of PVDF membranes in areas such as membrane based gas absorption and membrane distillation where no substantial commercial PVDF membrane processes are available so far.  相似文献   

2.
Two poly(vinylidene fluoride) (PVDF) membrane modification approaches, i.e., poly(vinylpyrrolidone) (PVP) modification and sulfonation, were applied and investigated to produce a fouling‐resistant membrane for microalgae filtration. Both methods were able to alter the membrane surface to become more hydrophilic. However, clean water permeance increased only for the PVP‐modified membranes, while the sulfonated membranes underwent a significant morphology transformation to a denser membrane and thus lower permeance. Microalgae filtration with PVP‐modified membranes showed less fouling compared to the pristine one, particularly in the beginning of the filtration, indicating that fouling reduction on these membranes mainly occurs in the initial fouling stage. Fouling is also found to be influenced by the microalgae species, possibly due to the different properties of the formed cake layer.  相似文献   

3.
对聚偏氟乙烯分离膜的亲水化改性方法进行了综述,分析了物理改性、化学改性、等离子体改性以及辐照接枝改性等方法的特点及改性效果,并指出化学改性是从根本上实现了聚偏氟乙烯膜的亲水化改性。  相似文献   

4.
In this study, crosslinked polymer electrolyte membranes for polymer electrolyte membrane fuel cell (PEMFC) applications are prepared using electron beam irradiation with a mixture of sulfonated poly(ether ether ketone) (SPEEK), poly(vinylidene fluoride) (PVDF), and triallyl isocyanurate (TAIC) at a dose of 300 kGy. The gel‐fraction of the irradiated SPEEK/PVDF/TAIC (95/4.5/0.5) membrane is 87% while the unirradiated membrane completely dissolves in DMAc solvent. In addition, the water uptake of the irradiated membrane is 221% at 70 °C while that of the unirradiated membrane completely dissolves in water at above 70 °C. The ion exchange capacity and proton conductivity of the crosslinked membrane are 1.57 meq g−1, and 4.0 × 10−2 S cm−1 (at 80 °C and RH 90%), respectively. Furthermore, a morphology study of the membranes is conducted using differential scanning calorimetry and X‐ray diffractometry. The cell performance study with the crosslinked membrane demonstrates that the maximum power density is 518 mW cm−2 at 1036 mA cm−2 and the maximum current density at applied voltage of 0.4 V is 1190 mA cm−2.  相似文献   

5.
In this study, an antifouling poly(vinylidene fluoride) (PVDF) hollow‐fiber membrane was fabricated by blending with silver‐loaded graphene oxide via phase inversion through a dry‐jet, wet‐spinning technique. The presence of graphene oxide endowed the blended membrane with a high antifouling ability for organic fouling. The permeation fluxes of the blended membrane was 3.3 and 2.9 times higher than those of a pristine PVDF membrane for filtering feed water containing protein and normal organic matter, respectively. On the other hand, the presence of silver improved the antibiofouling capability of the blended membrane. For the treatment of Escherichia coli suspension, the permeation flux of the blended membranes was 8.2 times as high as that of the pristine PVDF membrane. Additionally, the presented blended membrane improved the hydrophilicity and mechanical strength compared to those of the pristine PVDF membrane, with the water contact angle decreasing from 86.1 to 62.5° and the tensile strength increasing from 1.94 to 2.13 MPa. This study opens an avenue for the fabrication of membranes with high permeabilities and antifouling abilities through the blending of graphene‐based materials for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44713.  相似文献   

6.
《塑料》2015,(6)
采用N,N-二甲基甲酰胺(DMF)、N-甲基吡咯烷酮(NMP)为溶剂制备了聚偏氟乙烯(PVDF)薄膜,采用色差、FT-IR的分析方法,研究了PVDF薄膜在氢氧化钠水溶液中的碱腐蚀行为。结果表明:溶剂法PVDF的耐碱腐蚀性能远低于热压法PVDF,残留溶剂NMP、DMF可加剧PVDF的碱腐蚀,并在PVDF表面产生了共轭多烯结构。酰胺类溶剂NMP、DMF遇碱分解生成的有机胺是导致溶剂法PVDF不耐碱腐蚀的根本原因。添加5%的氟碳阴离子表面活性剂可有效解决溶剂法PVDF不耐碱腐蚀的问题。  相似文献   

7.
Covalent immobilization of polycations onto a membrane surface has been shown to significantly improve the resistance to biofouling. The poly(vinylidene fluoride)‐graft‐poly(N,N‐dimethylamino‐2‐ethylmethacrylate) (PVDF‐g‐PDMAEMA) copolymer was synthesized via radical grafting copolymerization and fabricated into a flat membrane. The polycation membrane surface was constructed by quaternization of PDMAEMA side chains with 1,5‐dibromopentane and diquaternization of 4,4′‐bipyridine. As revealed by membrane surface morphology, pore size, and porosity measurement, the polycations are distributed on the membrane surface and internal pore channel surface. Water contact angles confirm that the incorporation of polycations remarkably promotes the surface hydrophilicity of a membrane. The polycation membrane surface provides an excellent bactericidal efficiency against Escherichia coli.  相似文献   

8.
The relationship between the pressure, volume, and temperature (PVT) of poly(vinylidene fluoride) homopolymers (PVDF) and poly(vinylidene fluoride)–hexafluoropropylene (PVDF–HFP) copolymers was determined in the pressure range of 200–1200 bar and in the temperature range of 40°C–230°C. The specific volume was measured for two homopolymers having a molecular weight (Mw) of 160,000–400,000 Da and three copolymers containing between 3 and 11 wt % HFP with a molecular weight range of 320,000–480,000 Da. Differential scanning calorimetry (DSC) was used to simulate the cooling process of the PVT experiments and to determine the crystallization temperature at atmospheric pressure. The obtained results were compared to the transitions observed during the PVT measurements, which were found to be pressure dependent. The results showed that the specific volume of PVDF varies between 0.57 and 0.69 cm3/g at atmospheric pressure, while at high pressure (1200 bar) it varies between 0.55 and 0.64 cm3/g. For the copolymers, the addition of HFP lowered its melting point, while the specific volume did not show a significant change. The TAIT state equation describing the dependence of specific volume on the zero‐pressure volume (V0,T), pressure, and temperature has been used to predict the specific volume of PVDF and PVDF–HFP copolymers. The experimental data was fitted with the state equation by varying the parameters in the equation. The use of the universal constant, C (0.0894), and as a variable did not affect the predictions significantly. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 230–241, 2001  相似文献   

9.
聚偏氟乙烯膜的亲水性改性研究进展   总被引:11,自引:0,他引:11  
唐广军  孙本惠 《化工进展》2004,23(5):480-485
疏水性聚合物膜的亲水性改性是当前分离膜研究的热点之一。从膜表面亲水改性和膜材料亲水性改性的角度出发,综述了聚偏氟乙烯(PVDF)分离膜的各种改性方法的特点及改性效果,分析了其亲水改性机理,指出膜材料共混改性是今后发展的主要方向。  相似文献   

10.
作为一种新型改性方法,电晕诱导接枝进行聚合物微孔膜表面改性具有设备简单、可连续运行、不破坏膜本体结构、操作条件温和、辐照强度均匀以及产物纯净等优点。本研究中,使用电晕处理设备对自制PVDF平板膜表面进行了电晕放电处理,电压为8~12kV,处理时间为20~100s。然后将其浸入丙烯酸溶液中进行接枝聚合反应,单体浓度为15vt%,反应温度为50℃,反应时间为5小时。研究该方法可行,并且接枝效果和电晕电压、电晕时间、接枝时间和单体浓度成正比。  相似文献   

11.
Severe fouling to poly(vinylidene fluoride) (PVDF) membrane is usually caused as filtrating the papermaking wastewater in the ultrafiltration (UF) process. In the paper, fouling behavior and mechanism were investigated, and the low-concentration polyvinyl alcohol (PVA) contained in the sedimentation tank wastewater was found as the main foulant. Consequently, the corresponding cleaning approach was proposed. The experiment and modeling results elaborated that the fouling mode developed from pore blockage to cake layer along with filtration time. Chemical cleaning conditions including the composition and concentration of reagents, cleaning duration and trans-membrane pressure were investigated for their effect on cleaning efficiency. Pure water flux was recovered by over 95% after cleaning the PVDF membrane using the optimal conditions 0.5 wt% NaClO (as oxidant) and 0.1 wt% sodium dodecyl benzene sulfonate (SDBS, as surfactant) at 0.04 MPa for 100 min. In the chemical cleaning method, hypochlorite (ClO) could first chain-scissor PVA macromolecules to small molecules and SDBS could wrap the fragments in micelles, so that the foulants were removed from the pores and surface of membrane. After eight cycling tests, pure water flux recovery maintained above 95% and the reused membrane was found intact without defects.  相似文献   

12.
Poly(vinylidene fluoride) (PVDF) powders were grafted with N‐vinyl pyrrolidone using the pre‐irradiation induced graft polymerization technique. The effects of reaction time, absorbed dose, and monomer concentration on the degree of grafting were investigated, and the grafted PVDF powders were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The grafted PVDF powders were also cast into microfiltration (MF) membranes via the phase‐inversion method. The contact angle and water uptake were measured. The membrane morphology was studied by scanning electron microscopy, and the water filtration properties of the membranes were tested. The antifouling properties were determined through measurements of the recovery percentage of pure water flux after the MF membranes were fouled with bovine serum albumin solution. The results confirmed that the existence of poly(N‐vinyl pyrrolidone) (PVP) graft chains improved the hydrophilicity and antifouling properties of the MF membranes cast from PVDF‐g‐PVP powders. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

13.
Attempts were made to spin hollow-fiber membranes from poly(vinylidene fluoride) (PVDF) material by the dry–wet phase inversion method. Hollow fibers so prepared were characterized for various parameters and by electron microscopic techniques. Membranes were also tested for the separation of water/1-propanol mixtures in vapor phase. It was found that the hollow fibers were water selective despite the fact that PVDF material is hydrophobic. Intrinsically organic selective property of PVDF material was proved by coating a porous polyetherimide membrane with a PVDF layer, which resulted in enhancement of 1-propanol permeation while suppressing the permeation of water. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1263–1270, 1997  相似文献   

14.
以3种不同聚合度的聚乙烯醇(PVA0588、PVA1788、PVA2488)为原料,添加相同质量分数的碱木质素采用流延法制备共混膜。采用电子万能试验机、扫描电子显微镜、热重分析仪等分析手段对共混膜进行分析表征,并测定了共混膜在不同极性溶剂中力学性能的变化。结果表明:在碱木质素添加量为15%时,碱木质素可较好地分散于PVA相中,3种共混膜的力学性能与各自对应的纯PVA膜相比都有了一定的提高,且当聚合度由PVA0588变化到PVA2488时,共混膜的拉伸强度从35.16MPa增加到48.30MPa,提高了37.37%,断裂伸长率从172.22%增加到247.08%,提高了43.47%;由于PVA聚合度的增大和碱木质素的添加,均使得共混膜的耐溶剂性能和热稳定性增加。  相似文献   

15.
Membrane fouling is the key problem that occurs in membrane process for water treatment. However, how membrane microstructure influences the fouling behavior is still not clear. In this study, fouling behavior caused by dextran was deeply and systematically investigated by employing four poly(vinylidene fluoride)(PVDF)membranes with different pore sizes, ranging from 24 to 94 nm. The extent of fouling by dextran was accurately characterized by pore reduction, flux decline, and the change of critical flux. The result shows that membrane with the smallest pore size of 24 nm experienced the smallest fouling rate and the lowest fouling extent. As the membrane pore size increased, the critical flux ranges were 105-114, 63-73, 38-44 and 34-43 L·m~(-2)·h~(-1),respectively. The critical flux and fouling resistances indicated that the fouling propensity increases with the increase of membrane pore size. Two pilot membrane modules with mean pore size of 25 nm and 60 nm were applied in membrane filtration of surface water treatment. The results showed that serious irreversible membrane fouling occurred on the membrane with pore size of 60 nm at the permeate flux of40.5 L·m~(-2)·h~(-1).On the other hand, membrane with pore size of 25 nm exhibited much better anti-fouling performance when permeate flux was set to 40.5,48 and 60 L·m~(-2)·h~(-1).  相似文献   

16.
Fu Liu  Bao-Ku Zhu  You-Yi Xu 《Polymer》2007,48(10):2910-2918
Poly(vinylidene fluoride) (PVDF) membrane was pre-irradiated by electron beam, and then poly(ethylene glycol) methyl ether methacrylate (PEGMA) was grafted onto the membrane surface in the aqueous solution. The degree of grafting was significantly influenced by the pH value of the reaction solution. The surface chemical changes were characterized by the Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Combining with the analysis of the nuclear magnetic resonance proton and carbon spectra (1H NMR and 13C NMR), PEGMA was mainly grafted onto the membrane surface. Morphological changes were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The porosity and bulk mean pore size changes were determined by a mercury porosimeter. The surface and bulk hydrophilicity were evaluated on the basis of static water contact angle, dynamic water contact angle and the dynamic adsorption process. Furthermore, relative high permeation fluxes of pure water and protein solution were obtained. All these results demonstrate that both hydrophilicity and fouling resistance of the PVDF membrane can be improved by the immobilization of hydrophilic comb-like polymer brushes on the membrane surface.  相似文献   

17.
Frank Abraham 《Polymer》2010,51(4):913-69
This paper presents 1,3,5-benzenetrisamides as colorless α-nucleating agents for poly(vinylidene fluoride). In order to screen a large variety of 1,3,5-benzenetrisamide derivatives with respect to their nucleating potential an efficient and reliable test based on polarized light microscopy was established. For selected promising compounds the concentration dependence of the PVDF crystallization temperature, the dissolution behavior of the additive in the polymer melt, and the crystallization of the additive from the polymer melt was investigated in a concentration range between 1 wt% (10,000 ppm) and 70 ppm. It was found, that only two of the investigated compounds were able to raise the crystallization temperature about 8 °C at a concentration of 140 ppm and 580 ppm, respectively. These trisamides have the advantage being soluble in the polymer melt, not featuring absorption of visible light and therefore allowing the preparation of uniform and colorless PVDF products.  相似文献   

18.
The polymer poly(vinylidene fluoride) (PVDF) was irradiated with X-rays produced by a nonmonochromatic (MgKα) source and the structural and electronic PVDF surface modifications were studied by X-ray photoelectron spectroscopy (XPS). Changes in the shape and intensity of the C1s and F1s lines show that a PVDF degradation consisting of the polymer defluorination takes place. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2125–2129, 1998  相似文献   

19.
The preparation of very hydrophobic poly(vinylidene fluoride) (PVDF) membranes was explored by using two methods. The first one was the modified phase inversion method using a water/N,N‐dimethylacetamide (DMAc) mixture instead of pure water as a soft precipitation bath. The second method was a precipitation‐bath free method, that is, the PVDF/DMAc casting solution underwent gelation in the open air instead of being immersed into a precipitation bath. The morphology of the surface and cross section of the membranes was investigated by using scanning electron microscopy (SEM). It was found that the membranes exhibited certain micro‐ and nanoscale hierarchical roughness on the surface, which brought about an enhanced hydrophobicity of the membrane. The contact angle (CA) of the samples obtained by the second method was as high as 150° with water. The conventional phase inversion method preparing PVDF porous membrane using pure water as precipitation bath usually results in an asymmetric membrane with a dense skin layer having a CA close to that of a smooth PVDF surface. The modified approach avoided the formation of a skin‐layer and resulted in a porous and highly hydrophobic surface of PVDF. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1358–1363, 2005  相似文献   

20.
综述了聚偏氟乙烯树脂的性能、其熔体的流变特性及在熔融加工领域的广泛应用,详细介绍了剪切变稀的非牛顿流体流变行为及其影响因素。通过分子链支化、共混和共聚可改善PVDF熔体的流变性能,以满足不同性能制品的需求以及进一步拓宽熔融加工成型方法。  相似文献   

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