氟树脂改性石棉隔膜简述

在研制改性石棉隔膜的过程中,考虑工艺路线,原材料的品种规格,以及改性石棉隔膜的制膜方法,参阅了部分有关资料,作了摘录和正理。本文就电解槽隔膜;改性石棉隔膜;氟树脂改性石棉隔膜的制膜方法;用于增强石棉隔膜的氟树脂分述如下。     

氟聚合物多层膜的加工方法

美国Chemfab公司发明了一种制造多层氟聚合物流延膜的加工技术,用这种新技术制得的氟聚合物膜可热压到抗塑性或热固性树脂的基材上,而不需要任何粘合剂,此膜对基材的粘附力极强,且具有一切氟聚合     

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。     

聚偏二氟乙烯增强型微孔膜的研制

本文讨论了聚偏二氟乙烯浓度,添加剂种类及其浓度,空气中溶剂挥发时间,凝胶浴温度对膜性能的影响,通过控制适当的制膜条件,可以制成高通量的０．２２μｍ至３．０μｍ系列的聚偏二氟乙烯增强型微孔膜。     

聚偏氟乙烯中空纤维膜的研制

本文选用聚偏氟乙烯作为膜材料,二甲基甲酰胺为溶剂,聚乙二醇为添加剂,采用湿法纺丝成膜,对影响膜性能的诸因素进行了讨论,用所制的中空纤维膜组件对TNT废水进行了膜萃取实验。用回归正交实验设计确定的最佳配方为聚偏氟乙烯浓度22.14%,聚乙二醇浓度6.26%,二甲基甲酰胺71.60%,纺丝温度54.84℃。该最优组合膜的萃取速率为1.898mg/m     

电解制氟

本文阐述了电解制氟原理,制氟工艺与特征,异常现象的原因与排除,以及元素氟的最新应用等问题。     

有机氟改性苯丙乳液

华中师范大学的高献英等人将有机氟和有机硅同时用于苯丙乳液的改性，当有机氟与有机硅的质量比为1～3：1时，所制得的乳胶膜的吸水率为5．4％，界面张力为28．3mN／m，涂膜硬度为0．72。     

电解制氟技术研究进展

对电解制氟技术进行回顾和总结。综述了制氟电解槽电子、热量、质量和两相动量传递及多场耦合仿真模拟研究进展，以及电解制氟设备及工艺改进提升方面的研究进展。     

聚苯乙烯/聚偏氟乙烯阳离子交换合金膜的研制与性能

以聚偏氟乙烯为离子交换膜基体材料,将它溶解后再与苯乙烯和二乙烯苯混合,随后热引发交联共聚,得到胶状物;再经过挤出、固化、造粒、干燥、粉碎等高分子物理加工处理,得到聚苯乙烯/聚偏氟乙烯合金粉末,磺化后制备出阳离子交换粉;采用类似于异相膜生产的热压成型方法,制得具有半互穿网络结构的聚苯乙烯/聚偏氟乙烯阳离子交换合金膜。性能测试表明,膜面电阻为4.8Ω·cm2,阳离子选择透过率为96.2%,电渗析脱盐综合性能明显优于国产异相膜,与国外均相膜接近。     

膜蒸馏用聚偏氟乙烯微孔膜的结构控制 Ⅲ.制膜条件的选择和膜蒸馏性能

为了提高聚偏氟乙烯微孔膜的膜蒸馏通量,本文对制膜条件进行了综合控制,在铸膜液中加入了丙酮溶胀剂,并采用乙醇水溶液作凝固浴。研究了挥发时间和凝固浴中乙醇含量对膜形态结构的影响。比较了由不同制膜条件制得的膜的膜蒸馏性能。结果表明,适当选择制膜条件,能得到膜蒸馏性能优良的膜。其截留率近于100%。在暖侧温度为55℃、冷侧温度为25℃时,膜的膜蒸馏通量可达22.5 kg/(m~2·h),已接近反渗透膜的水平。     

聚偏氟乙烯-六氟丙烯接枝聚丙烯酸磺酸丙酯制备质子膜

以聚偏氟乙烯(PVDF)-六氟丙烯(HFP)中PVDF的仲氟原子直接引发甲基丙烯酸(3-磺酸钾)丙酯(SPMA)的原子转移自由基聚合,成功得到以PVDF-HFP为主链、侧链含磺酸基团的接枝聚合物(PVDF-HFP-g-PSPMA)质子交换膜. 通过红外、核磁分析方法对PVDF-HFP-g-PSPMA的结构进行表征. 反应不同时间得到的PVDF-HFP-g-PSPMA离子交换容量为0.051~0.59 meq/g,质子传导率为(2.58~30.9)×10-2 S/m.     

Unsupported electrospun membrane for water desalination using direct contact membrane distillation

In this project, an unsupported electrospun poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) membrane was used for water desalination using direct contact membrane distillation (DCMD). The membrane was electrospun using a laboratory-scale machine with multiple nozzles that was developed in-house. Critical process parameters, including the applied voltage and polymer concentration, were optimized to obtain bead-free electrospun membranes with fiber diameters less than 300 nm. To improve the membrane thermal stability and performance, the selected electrospun membrane was heat-pressed at 160°C. The untreated and heat-pressed membranes were tested in a DCMD setup at different feed temperatures (60, 70, and 80°C) and feed flow rates (0.4, 0.6, and 0.8 L/min), while maintaining the permeate temperature and flow rate at 20°C and 0.2 L/min, respectively. The modified electrospun membrane exhibited a very high permeate flux (>37.5 kg/m²/h) and a salt rejection rate of 99.99% at a feed temperature of 70°C. The performance of the heat-pressed unsupported PVDF-HFP electrospun membrane was nearly identical to a commercially available polytetrafluoroethylene (PTFE) supported membrane. These promising results demonstrate that relatively low-cost electrospun membranes can be easily produced and successfully used in DCMD to minimize the capital cost and increase the energy efficiency of the process.     

Preparation and properties of gel membrane containing porous PVDF-HFP matrix and cross-linked PEG for lithium ion conduction

Lithium ion conducting membranes are the key materials for lithium batteries. The lithium ion conducting gel polymer electrolyte membrane (Li-GPEM) based on porous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix and cross-linked PEG network is prepared by a typical phase inversion process. By immersing the porous PVDF-HFP membrane in liquid electrolyte containing poly(ethylene glycol) diacrylate (PEGDA) and an initiator to absorb the liquid electrolyte at 25°C, and then thermally cross-linking at 60°C, the Li-GPEM is fabricated successfully. The measurements on its weight loss, mechanical and electrochemical properties reveal that the obtained Li-GPEM has better overall performance than the liquid and blend gel systems used as conductive media in lithium batteries. The ionic conductivity of the fabricated Li-GPEM can reach as high as 2.25 × 10^-3 S/cm at 25°C.     

Nanocrystalline cellulose reinforced PVDF-HFP membranes for membrane distillation application

Polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP) membranes containing different amounts of nanocrystalline cellulose (NCC) were fabricated by electrospining technique for application in membrane distillation (MD). The effect of incorporating NCC on the mechanical strength, morphology, pore size distribution, and liquid entry pressure (water) of the fibrous was investigated. Incorporation of NCC in PVDF-HFP matrix improved the tensile strength and Young's modulus and narrowed down the pore size distribution of the fabricated membranes. Liquid entry pressure, which is an important parameter to ensure high salt rejection of the membranes in MD, was improved from ~ 19 psi to ~ 27 psi with the addition of 2 wt.% NCC. Fabricated membranes were tested in direct contact membrane distillation (DCMD). MD operation data revealed water flux of 10.2–11.5 Lh^− 1 m^− 2 with salt rejection of 99% for these NCC-incorporated membranes.     

Improvement of porous polyvinylidene fluoride-co-hexafluropropylene hollow fiber membranes for sweeping gas membrane distillation of ethylene glycol solution

Porous polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) hollow fiber membranes were fabricated through a wet spinning process. In order to improve the membrane structure, composition of the polymer solution was adjusted by studying ternary phase diagrams of polymer/solvent/non-solvent. The prepared membranes were used for sweeping gas membrane distillation (SGMD) of 20 wt% ethylene glycol (EG) aqueous solution. The membranes were characterized by different tests such as N₂ permeation, overall porosity, critical water entry pressure (CEP_w), water contact angle and collapsing pressure. From FESEM examination, addition of 3 wt% glycerol in the PVDF-HFP solution, produced membranes with smaller finger-likes cavities, higher surface porosity and smaller pore sizes. Increasing the polymer concentration up to 21 wt% resulted in a dense spongy structure which could significantly reduce the N₂ permeance. The membrane prepared by 3 wt% glycerol and 17 wt% polymer demonstrated an improved structure with mean pore size of 18 nm and a high surface porosity of 872 m^-1. CEP_w of 350 kPa and overall porosity of 84% were also obtained for the improved membrane. Collapsing pressure of the membranes relatively improved by increasing the polymer concentration. From the SGMD test, the developed membrane represented a maximum permeate flux of 28 kg·m^-2·h^-1 which is almost 19% higher than the flux of plain membrane. During 120 h of a long-term SGMD operation, a gradual flux reduction of 30% was noticed. In addition, EG rejection reduced from 100% to around 99.5% during 120 h of the operation.     

Dye-sensitized solar cells based on electrospun poly(vinylidenefluoride-co-hexafluoropropylene) nanofibers

Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers were prepared by the electrospinning method and used as polymer electrolytes in dye-sensitized solar cells (DSSCs). The electrolyte uptake and ionic conductivity of electrospun PVDF-HFP nanofibers with different diameters changed significantly, regardless of the nanofiber thickness. The PVDF-HFP nanofibers prepared from a 15 wt% spinning solution showed high ionic conductivity (1.295 S/cm) and electrolyte uptake (947 %). DSSCs based on the 15 wt% PVDF-HFP nanofiber electrolyte showed an electron transit time of 6.34 × 10^?3 s, electronic recombination time of 5.88 × 10^?2 s, and conversion efficiency of 3.13 %. Thus, we concluded that the electrospun PVDF-HFP nanofibers can be used as polymer electrolytes in flexible DSSCs as well.     

Improvement of porous polyvinylidene fluoride-co-hexafluropropylene hollow fiber membranes for sweeping gas membrane distillation of ethylene glycol solution

Porous polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) hollow fiber membranes were fabricated through a wet spinning process. In order to improve the membrane structure, composition of the polymer solution was adjusted by studying ternary phase diagrams of polymer/solvent/non-solvent. The prepared membranes were used for sweeping gas membrane distillation (SGMD) of 20 wt% ethylene glycol (EG) aqueous solution. The membranes were characterized by different tests such as N₂ permeation, overall porosity, critical water entry pressure (CEP_w), water contact angle and collapsing pressure. From FESEM examination, addition of 3 wt% glycerol in the PVDF-HFP solution, produced membranes with smaller finger-likes cavities, higher surface porosity and smaller pore sizes. Increasing the polymer concentration up to 21 wt% resulted in a dense spongy structure which could significantly reduce the N₂ permeance. The membrane prepared by 3 wt% glycerol and 17 wt% polymer demonstrated an improved structure with mean pore size of 18 nm and a high surface porosity of 872 m⁻¹. CEP_w of 350 kPa and overall porosity of 84% were also obtained for the improved membrane. Collapsing pressure of the membranes relatively improved by increasing the polymer concentration. From the SGMD test, the developed membrane represented a maximum permeate flux of 28 kg·m⁻²·h⁻¹ which is almost 19% higher than the flux of plain membrane. During 120 h of a long-term SGMD operation, a gradual flux reduction of 30% was noticed. In addition, EG rejection reduced from 100% to around 99.5% during 120 h of the operation.     

Semi-interpenetrating gel polymer electrolyte based on PVDF-HFP for lithium ion batteries

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolyte (GPE) is considered one of the promising candidate electrolytes in the polymer lithium ion battery (LIB) because of its free standing, shape versatility, security, flexibility, lightweight, reliability, and so on. However, the pristine PVDF-HFP GPE cannot still meet the requirement of large-scale LIBs and other electrochemical devices due to its relatively low ionic conductivity and deterioration of mechanical strength caused by the incorporation of organic liquid electrolyte into the polymer matrix as well as high cost. In order to overcome above deficiencies of PVDF-HFP based GPE, ultraviolet (UV)-curable semi-interpenetrating polymer network is designed and synthesized through UV-irradiation technique, and the as-prepared semi-interpenetrating matrix is constituted by pentaerythritol tetracrylate polymer network and PVDF-HFP. The ionic conductivity of the optimized GPE is as high as 5 × 10⁻⁴ S/cm and electrochemical window is up to 4.8 V at room temperature. Especially, the LIB prepared by GPE shows the high initial discharge specific capacity of 151 mAh/g at 0.5 C and good rate capability. Therefore, the semi-interpenetrating GPE based on PVDF-HFP exhibits a promising prospect for the application of rechargeable LIBs.     

Gel electrolyte membranes derived from co-continuous polymer blends

Polymer gel electrolyte membranes were prepared by first casting films of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt, and poly(ethylene glycol) (PEG) monomethacrylate and dimethacrylate macromonomers. Polymerization of the macromonomers initiated by UV-irradiation then generated solid films having phase-separated morphologies with a microporous PVDF-HFP phase embedded in PEG-grafted polymethacrylates. Gel electrolyte membranes were finally prepared by allowing the films to take up solutions of LiTFSI in γ-butyrolactone (γ-BL). The PEG-grafted polymethacrylate in the membranes was found to host the largest part of the liquid electrolyte, giving rise to a highly swollen ionic conductive phase. Results by FTIR spectroscopy showed that the Li⁺ ions preferentially interacted with the ether oxygens of the PEG chains. The properties of the membranes were studied as a function of the ratio of PVDF-HFP to PEG-grafted polymethacrylate, as well as the degree of crosslinking, LiTFSI concentration, and liquid electrolyte content. The self-supporting and elastic gel membranes had ionic conductivities of 10⁻³ S cm⁻¹ and a mechanical storage modulus in the range of 2.5 MPa in the tension mode at room temperature. Variation of the salt concentration showed the greatest effect on the membrane properties.     

New method for the preparation of solid polymer electrolyte based on poly(vinylidene fluoride-co-hexafluoropropylene)

A novel solid polymer electrolyte (pore-gel SPE) has been found to provide superior SPE having a high conductivity, good mechanical strength and low solution leakage. This pore-gel SPE was prepared from gelation in pores of polymer membrane with electrolyte solution including solvent. The conductivity of pore-gel type PVDF-HFP/ TEABF₄ (Tetraethylammomium tetrafluoroborate) membrane can reach 1.6×10^-1 Scm^-1. The tensile strength of this membrane was 4,000 kPa, which is about 23 times larger than that of gel-type SPE with the same composition. Poregel SPE reduced solution leakage to 0%, compared with 2% of hybrid-type SPE after 2.0 hr leakage test in PVDFHFP/ TEABF₄ membrane.