PVDF -co-HFP

Capacitors made of high-surface carbon with PVdF-co-HFP as a binder and filled with neat ionic liquids, without any molecular solvent, show high specific capacity, up to 180 F/g [13],... 

Attempts to blend Nation with another polymer have mostly focused on the use of PVDF (as well as its copolymer, PVDF-co-HFP). This is probably due to its chemical and thermal stability as well as to its semicrystalline nature, thus introducing increased mechanical strength to the However,... 

Kalyana Sundaram, N.T., Subramania, A., 2007. Nano-size UAIO2 ceramic fUler incorporated porous PVDF-co-HFP electrolyte for lithium-ion battery applications. Electrochim. Acta 52,4987—4993. 

Flexible supercapacitors were made from PEDOT nanolibers as electrodes and polyacrylonitrile (PAN) nanolibers as separator by Larfogue et al. [19]. The PEDOT nanolibers were produced by combination of electrospinning and vapor-phase polymerization to form a conductive mat, and were used as the active material (electrodes), separated by a sheet of PAN nanolibers. Carbon-based clothes were used as the current collectors. The material layers were stacked together and embedded in a solid electrolyte containing an ionic liquid and polyvinylidene lluoride-co-hexa-fluoro-propylene (PVDF-co-HFP) as the host polymer. 

Nafion-115, Nafion-112, and Nafion-212 which have thickness of 175 pm, 125 pm, 50 pm, and 50 pm, respectively. These thiimer composite PEMs contain significantly less amounts of the expensive Nafion resin than the thicker neat Nafion membranes. Thus, another advantage of Nafion/PTFE composite PEMs is the fact that they are inexpensive. Besides porous PTFE films, porous films such as polyethylene (PE) [21, 22] and electro-sptm polymer nanofiber films such as those of poly(vinyhdene fluoride) (PVdF) [23, 24], poly(vinyhdene fluoride-co-hexafluoropropylene) (PVdF-co-HFP) [25], and poly(vinyl alcohol) (PVA) [26-31] have also been used as supporting films for impregnating Nafion ionomer solutions to prepare Nafion/fiber composite PEMs for PEMFC and DMFC applications. 

Similar to the preparation of Nafion/nano-fiber composite PEMs using electro-spun PVdF [23, 24], PVdF-co-HFP [25], and PVA nanofiber films [26-31] as supporting films for impregnating Nafion ionomer solutions, the... 

Su and co-workers employed two kinds of ENM made of PVDF and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) in DCMD. The authors optimized the feed solution flow rate and temperature differences for better permeate flux and salt rejection. Furthermore, the effect of hydrophobicity of... 

Subramania A, Sundaram NTK, Kumar GV (2006) Structural and electrochemical properties of micro-porous polymer blend electrolytes based on PVdF-co-HFP-PAN for Li-ion battery applications. J Power Sourc 153 177-182... 

Soresi et al. [53] grafted styrene onto PVDF film and its copolymer with hexa-fluropropylene [P(VDF-co-HFP)] and found that membranes based on P(VDF-co-HFP) achieve degree of grafting of 100% with conductivity >60 mS cm" at 90% relative humidity. Full characterization and fuel cell performance of these membranes was not revealed. 

Figure 2 [24,118] shows the infrared spectrum of uncured poly(VDF-co-HFP) copolymer (FKM gum), before and after a thin film of polymer is heated in air at 300 °C. Two new bands centered at 1580 and 1750 cm appeared after heating, which are assigned to the conjugated double bonds and to the - CH = CF2 end groups, respectively. Unsaturation is likely to be caused by elimination of HF from PVDF block of the FKM chain, in particular from the head-to-tail position of the structure. 

Table 18 [52] reports the d.o.g. (%) of different membranes under the same experimental conditions. The difference in d.o.g. between the homopolymer and the dense-membrane copolymer is evident. A 100% grafting yield is detected in the case of the poly(VDF-co-HFP) copolymer, whereas 6% is the d.o.g. obtained in the case of the PVDF membrane. This difference can be due to the different compatibility of the two polymers with styrene, and the kinetics of grafting which is faster in the case of the copolymer. Hence, irra-... 

Tablets d.o.g. (degree of grafting) of starting membranes of PVDF and poly(VDF-co-HFP)copolymer [52] ...

A PVDF and a poly(VDF-co-HFP) copolymer were irradiated by Kr ions at 6.2 MeV/amu energy [47]. The evolution of the insoluble F fraction versus the absorbed dose D, and the fluence is represented in Fig. 29 [47]. In both cases, an increase of the gel fraction F as the absorbed dose increases is observed. 

A poly(VDF-co-HFP) copolymer is appHed to a metalhc substrate, as coating composition and crosslinked with amine, diamine, or ethoxysilane [192]. This cured polymer is used as thick or thin free standing films, or thick or thin films with good adhesion to metallic or other rigid surfaces [192]. Moreover, diamine-cured PVDF can be used as strong adhesive joints without prior surface modification [31]. 

Irradiated PVDF and poly(VDF-co-TrFE) copolymer possess ferroelectric properties that allow the use of such fluorinated polymer in the domain of captors, sensors, and detectors [47,194]. Another interesting property of crosslinked poly(VDF-co-HFP) copolymer is their insolubihty in organic solvent [195]. Cured fluorinated polymers can be processed as membranes for many electrochemical applications such as fuel cell and batteries [196]. For example, a poly(VDF-co-HFP) copolymer has been crossUnked with various systems such as polyols [197], by irradiation with electron beam or y-rays [197] or with aliphatic amines [198] in order to elaborate a solid polymer electrolyte for non aqueous lithium battery [197,198]. This electrolyte is particularly interesting for its ionic conductivity, its adhesion with an electro-conductive substrate and also remarkably enhanced heat resistance. 

Piperazine can crosslink poly(VDF-co-HFP) and poly(VDF-co-CTFE) copolymers at 57 °C in one day, whereas triethylene diamine and tetram-ethylethyldiamine can crosslink poly(VDF-co-CTFE) copolymer at 97 °C in one day. Finally, diethylene triamine crosslinks PVDF at 70 °C in 16 h. 

It is known that plasticized rubber, which is made of a copolymer of PVDF and HFP and impregnated with electrolyte solution, shows high ionic conductivity [37]. Thus by increasing the ratio of HFP to PVDF, the ionic conductivity and processability can be improved. A research team as Bellcore Co. Reported that if the HFP content is increased in the HFP/PVDF copolymer used as the polymer matrix, the melting point of the copolymer decreases. At 12% HFP, the copolymer can be processed at 120 to 130°C. A gel is prepared using an electrolyte composition of 1 mol/fLiPFg/EC/DMC, and this gel electrolyte was used for the 4-V... 

PEO, PVAc/PVdF and PVAc/P(VdF-co-HFP)which all have good mechanical performance and high ionic conductivity. 

Because of its excekent combination of properties, processibkity, and relatively low price compared to other fluoropolymers, PVDF has become the largest volume fluoropolymer after PTFE consumption in the United States has grown from zero in 1960 to about 6200 metric tons in 1991 (186). About 49% of the consumed volume is PVDF modified by copolymerization with 5—12-wt % HFP to enhance flexibkity. In 1992, Hst price for homopolymer powders was 15.32/kg, and for pekets 15.42/kg the reported market price was 14.09—14.22/kg (187). In the United States, almost ak PVDF is suppHed by Ausimont USA, Inc., Elf Atochem North America, Inc., and Solvay Polymers, Inc. Ausimont and Elf Atochem are producers Solvay is an importer of the resin. Smak amounts of resin are imported from Germany by Huls America, Inc, and from Japan by Kureha Chemical Industry Co., Ltd. PVDE producers and their trademarks are Hsted in Table 4. 

According to Tarascon and co-workers, the swelling of PVdF—HFP by liquid electrolytes was never complete due to the semicrystalline nature of the copolymer, which tends to microphase-separate after the activation by electrolyte. On the other hand, it is those crystalline domains in the gelled PVdF—HFP that provide mechanical integrity for the resultant GPE. Thus, a dual phase structure was proposed for the Bellcore GPE by some authors, wherein the amorphous domain swollen by a liquid electrolyte serves as the ion conduction phase, while tiny crystallites act as dimensional stabilizer. 

Improvements based on Bellcore technology were reported recently by Wunder and co-workers. Using PEG oligomers instead of DBP, they obtained the PVdF—HFP microporous films with the pore size increased from nanoscale to microscale, as shown in... 

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