Poly PVDF polymers

In order to determine the polymer chain orientation, infrared measurements of transmittance or absorbance must be performed with polarized IR radiation, parallel or perpendicular to the mechanical draw direction, for a particular absorption band of the spectrum. Fig. 7.11 shows the FTIR spectra obtained for two orthogonal polarization directions, parallel and perpendicular to the draw direction of a poly(vinylidene fluoride) (PVDF) polymer sample. It is possible to observe that the overall spectra are similar with neither modes being totally suppressed nor new modes seeming to appear. Nevertheless, the amount of IR radiation absorbed by some particular modes are clearly different for IR spectra obtained with radiation polarized in the perpendicular or parallel to the polymer draw direction (Fig. 7.11). 

Polymer Ferroelectrics. In 1969, it was found that strong piezoelectric effects could be induced in the polymer poly(vinyhdene fluoride) (known as PVD2 or PVDF) by apphcation of an electric field (103). Pyroelectricity, with pyroelectric figures of merit comparable to crystalline pyroelectric detectors (104,105) of PVF2 films polarized this way, was discovered two year later (106.)... 

Poly(viaylidene fluoride) [24937-79-9] is the addition polymer of 1,1-difluoroethene [73-38-7], commonly known as vinylidene fluoride and abbreviated VDF or VF2. The formula of the repeat unit in the polymer is —CH2—CF2—. The preferred acronym for the polymer is PVDF, but the abbreviation PVF2 is also frequently used. The history and development of poly(vinyhdene fluoride) technology has been reviewed (1 3). 

Unlike most crystalline polymers, PVDF exhibits thermodynamic compatibiUty with other polymers (133). Blends of PVDF and poly(methyl methacrylate) (PMMA) are compatible over a wide range of blend composition (134,135). SoHd-state nmr studies showed that isotactic PMMA is more miscible with PVDF than atactic and syndiotactic PMMA (136). MiscibiUty of PVDF and poly(alkyl acrylates) depends on a specific interaction between PVDF and oxygen within the acrylate and the effect of this interaction is diminished as the hydrocarbon content of the ester is increased (137). Strong dipolar interactions are important to achieve miscibility with poly(vinyhdene fluoride) (138). PVDF blends are the object of many papers and patents specific blends of PVDF and acryflc copolymers have seen large commercial use. 

Materials. For holographic information storage, materials are required which alter their index of refraction locally by spotwise illumination with light. Suitable are photorefractive inorganic crystals, eg, LiNbO, BaTiO, LiTaO, and Bq2 i02Q. Also suitable are photorefractive ferroelectric polymers like poly(vinyhdene fluoride-i o-trifluorethylene) (PVDF/TFE). Preferably transparent polymers are used which contain approximately 10% of monomeric material (so-called photopolymers, photothermoplasts). These polymers additionally contain different initiators, photoinitiators, and photosensitizers. 

Liquid polyalurninum chloride is acidic and corrosive to common metals. Suitable materials for constmction of storage and handling facilities include synthetic mbber-lined steel, corrosion resistant fiber glass reinforced plastics (FRP), ceramics, tetrafluoroethylene polymer (PTFE), poly(vinyhdene fluoride) (PVDF), polyethylene, polypropylene, and poly(vinyl chloride) (PVG). Suitable shipping containers include mbber-lined tank tmcks and rail cars for bulk shipment and plastic-lined or aH-plastic dmms and tote bins for smaller quantities. Except for aluminum chlorohydrates, PAG products are shipped as hazardous substances because of their acidity. 

Gozdz et al. (of Bellcore) [25] recognized that poly (vinylidene difluoride) hexafluoropropylene (PVDF HFP) copolymers could form gels with organic solvents and developed an entire battery based on this concept. Typically, the gel separator is 50 pm thick and comprises 60wt. % polymer. In the Bellcore process the separator is laminated to the electrodes under pressure at elevated temperature. The use of the PVDF HFP gelling agent increases the resistivity of the electrolyte by about five times which limits the rate capability of such batteries. 

Tadic et al. studied the polymer poly-vynilidene fluoride/hexa-fluoropropylene ( PVdF/HFP ) containing lithium salt solution in Ethylene carbonate/diethylene carbonate ( EC/DEC )- In order to understand better the effect of anion size in the electrolyte, two Li salts were compared, namely LiN(CF3S02)2 (termed Liimide by the authors) and LiN(C2F5S02)2 (termed Libeti ). 

Ionic polymers other than Nation have also been included in ionic/non-ionic PEM blends. Poly(ether sulfone) (PES) has been used to strengthen SPEEK as well as sulfonated poly(ether sulfone) (SPES) with contents ranging from 20 to 60 wt%. The conductivity of the SPEEK component was relatively the same as unmodified SPEEK up to about 40 wt%. A similar effect was seen for PES/SPES blends, although the drop in MeOH permeability was more dramatic for PES/SPES from unmodified SPES than for PES/SPEEK from unmodified SPEEK. PVDF has also been used as a blending material to reinforce SPEEK. s The strength of the PEM was increased over unmodified SPEEK. Although conductivity levels decreased as a function of increasing PVDF content, the selectivity (ratio of proton conductivity to MeOH permeability) of the blended PEMs was increased over that of unmodified SPEEK and Nation. 

Non-ionic polymers have also been blended with ionic block copolymers. Poly(vinyl phosphanate)-l7-polystyrene and PS-l -SPS have been blended with PPO. In both cases, improvements were seen in MeOH permeability over that of fhe unmodified block copolymers and conductivity values dropped as a function of increasing PPO confenf. PVDF has been blended wifh SEES in order fo improve its mechanical and chemical stability, but aggregation was found fo be a problem due fo incompafibility between components. However, it was found that a small amount (2 wt%) of a methyl methacrylate-butyl acrylate-methyl methacrylate block copolymer as com-patibilizer not only led to greater homogeneity but also improved mechanical resistance, water management, and conductivity. ... 

These types of separators consist of a solid matrix and a liquid phase, which is retained in the microporous structure by capillary forces. To be effective for batteries, the liquid in the microporous separator, which generally contains an organic phase, must be insoluble in the electrolyte, chemically stable, and still provide adequate ionic conductivity. Several types of polymers, such as polypropylene, polysulfone, poly(tetrafluoroethylene), and cellulose acetate, have been used for porous substrates for supported-liquid membranes. The PVdF coated polyolefin-based microporous membranes used in gel—polymer lithium-ion battery fall into this category. Gel polymer... 

Gel polymer lithium-ion batteries replace the conventional liquid electrolytes with an advanced polymer electrolyte membrane. These cells can be packed in lightweight plastic packages as they do not have any free electrolytes and they can be fabricated in any desired shape and size. They are now increasingly becoming an alternative to liquid-electrolyte lithium-ion batteries, and several battery manufacturers. such as Sanyo. Sony, and Panasonic have started commercial production.Song et al. have recently reviewed the present state of gel-type polymer electrolyte technology for lithium-ion batteries. They focused on four plasticized systems, which have received particular attention from a practical viewpoint, i.e.. poly(ethylene oxide) (PEO). poly (acrylonitrile) (PAN). ° poly (methyl methacrylate) (PMMA). - and poly(vinylidene fluoride) (PVdF) based electrolytes. ... 

The processability of fluorine-containing polymers is improved by replacement of one or more of the fluorine atoms. Replacing one of the eight fluorine atoms with a trifluoromethyl group gives a product called FEP or Viton, actually a copolymer of tetrafluoroethylene and hexafluoropropylene (Equation 6.53). Polytrifluoromonochloroethylene (PCTFE, Kel F) (Equation 6.54), in which one fluorine atom has been replaced by a chlorine atom, has a less regular structure and is thus more easily processed. Poly(vinylidene fluoride) (PVDF, Kynar) (Equation 6.55) is also more easily processable but less resistant to solvents and corrosives. 

The fluoropolymer family consists of polymers produced from alkenes in which one or more hydrogens have been replaced by fluorine. The most important members of this family are polytetrafluoroethylene (PTFE) (XLVII), polychlorotrifluoroethylene (PCTFE) (XLVIII), poly(vinyl fluoride) (PVF) (XLIX), poly(vinylidene fluoride) (PVDF) (L) copolymers of... 

Tlie use of polymer blends has been a very important approach in the development of new materials for evolving applications, as it is less costly than developing new polymers. The compatibility of poly(vinylidene fluoride) (PVDF) with various polymers has been comprehensively evaluated and has led to useful applications in coatings and films. Poly(methyl methacrylate) has been the most studied compatible polymer with PVDF owing to cost and performance advantages. Other acrylic polymers such as poly(ethyl methacrylate), poly(methyl acrylate), and poly(ethyl acrylate) have also been found to be compatible with PVDF. ... 

Coleman et al. 2471 reported the spectra of different proportions of poly(vinylidene fluoride) PVDF and atactic poly(methyl methacrylate) PMMA. At a level of 75/25 PVDF/PMMA the blend is incompatible and the spectra of the blend can be synthesized by addition of the spectra of the pure components in the appropriate amounts. On the other hand, a blend composition of 39 61 had an infrared spectrum which could not be approximated by absorbance addition of the two pure spectra. A carbonyl band at 1718cm-1 was observed and indicates a distinct interaction involving the carbonyl groups. The spectra of the PVDF shows that a conformational change has been induced in the compatible blend but only a fraction of the PVDF is involved in the conformational change. Allara M9 250 251) cautioned that some of these spectroscopic effects in polymer blends may arise from dispersion effects in the difference spectra rather than chemical effects. Refractive index differences between the pure component and the blend can alter the band shapes and lead to frequency shifts to lower frequencies and in general the frequency shifts are to lower frequencies. 

Kawai (1) and (2) (1969) found that polar polymer films such as PVDF, poly (vinyl fluoride), PVC, nylon 11, and polycarbonate exhibit a strong piezoelectricity when they are drawn and then polarized under a high cLc. field Ep at a high temperature Tp and cooled keeping the d.c. field. The piezoelectricity thus obtained depends on Ep, Tp, and poling period. An improved poling technique was reported by Edelman, Grisham, Roth, and Cohen (1970). 

Examples of fluoroplastics include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), ethylene—chlorotrifluoroethylene (ECTFE), ethylene—tetrafluoroethylene (ETFE), poly(vinylidene fluoride) (PVDF), etc (see Fluorine compounds, organic). These polymers have outstanding electrical properties, such as low power loss and dielectric constant, coupled with very good flame resistance and low smoke emission during fire. Therefore, in spite of their relatively high price, they are used extensively in telecommunication wires, especially for production of plenum cables. Plenum areas provide a convenient, economical way to run electrical wires and cables and to interconnect them throughout nonresidential buildings (14). Development of special flame-retardant low smoke compounds, some based on PVC, have provided lower cost competition to the fluoroplastics for indoors application such as plenum cable, Riser Cables, etc. 

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