Polyfvinylidene fluoride

Of greater interest in recent years have been the peculiar piezolectric properties"" of polyfvinylidene fluoride). In 1969 it was observed" that stretched film of the polymer heated to 90°C and subsequently cooled to room temperature in a direct current electric field was 3-5 times more piezoelectric than crystalline quartz. It was observed that the piezolectric strain coefficients were higher in the drawn film and in the normal directions than in the direction transverse to the film drawing. 

The piezoelectric phenomena have been used to generate ultrasonic waves up to microwave frequencies using thin polyfvinylidene fluoride) transducers. In the audio range a new type of loudspeaker has been introduced using the transverse piezolectric effect on a mechanically biased membrane. This development has been of considerable interest to telephone engineers and scientists. 

Likewise, poly (methyl methacrylate) and polyfvinylidene fluoride), the chemical structures of which are shown in Fig. 10.2, make a miscible blend because of the strong specific interactions between the oxygen atoms on the methacrylate and the fluoride group in the vinylidene fluoride group. 

Although Tyrann-M/E and even conventional membranes are superior to the new polyamide and polyfvinylidene fluoride) membranes with respect to flow rates and filtration capacities, the latter two are more suitable for filtration of most (but not all) organic solvents and, partially as a result of their lower void volumes (Table IV) exhibit mechanical and thermal properties which are generally superior to those of the cellulosics. It should also be noted that in the special case of fiber-reinforced membranes, the mechanical properties are predominantly functions of the embedded fibers rather than of the membrane structu reverse. 

Partially fluorinated polymers, notably polyfvinylidene fluoride) (PVDF) and its copolymers, are readily processed by conventional polymer technology and generally have chemi-... 

Conformational energy estimates are employed to determine the conformational characteristics of polyfvinyl fluoride) (PVF), polyfluoromethylene (PFM), and polytrifluoroethylene (PTF3). Effects of stereoconfiguration and, in the case of PVF and PTF3, the presence of head-to-head tail-to-tail (HH TT) defect structures are considered. The calculated results are compared to corresponding values found for polyfvinylidene fluoride), polytetrafluoroethylene, and polyethylene, and the equilibrium flexibilities of PVF, PFM, and PTF3 are discussed on this basis. 

Fig. 16. Complex electrostriction constant, k — in", for elongational strain in as-cast polyfvinylidene fluoride) film plotted against frequency (Hayakawa and...

Fig. 24. Piezoelectric stress constant of roll-drawn polyfvinylidene fluoride) films plotted against angle 0 between draw-axis and elongational strain (O) draw-ratio =2.1, ( ) draw-ratio = 1.6. Drawn after Nakamura and Wada [J. Polymer Sci. A-2,9,161 (1971)] by permission of John Wiley Sons, Inc.

Fig. 27. Hysteresis of apparent piezoelectric constant of roll-drawn polyfvinylidene fluoride) film at room temperature plotted against dc bias field. Draw-ratio = 7 (Oshiki and Fukada, 1972)...

Oshiki,M., Fukada,E. The inverse piezoelectricity and electrostriction in elongated and polarized films erf polyfvinylidene fluoride). Rep. Progr. Polymer Phys. Japan 14, 471 (1971). 

EOS models were derived for polymer blends that gave the first evidence of the severe pressure - dependence of the phase behaviour of such blends [41,42], First, experimental data under pressure were presented for the mixture of poly(ethyl acetate) and polyfvinylidene fluoride) [9], and later for in several other systems [27,43,44,45], However, the direction of the shift in cloud-point temperature with pressure proved to be system-dependent. In addition, the phase behaviour of mixtures containing random copolymers strongly depends on the exact chemical composition of both copolymers. In the production of reactor blends or copolymers a small variation of the reactor feed or process variables, such as temperature and pressure, may lead to demixing of the copolymer solution (or the blend) in the reactor. Fig. 9.7-1 shows some data collected in a laser-light-scattering autoclave on the blend PMMA/SAN [46],... 

Structure and Properties of Ferroelectric Copolymers of PolyfVinylidene Fluoride)... 

A large body of work has been developed by DeSimone and co-workers on the solubility of fluorinated polymers, especially polyfl,l-dihydroper-fluorooctylacrylate) fPFOA), in C02 (Hsiao et al., 1995 Luna-Barcenas et al., 1998). An excellent example of utilizing creative chemistry to design a C02-soluble polymer, PFOA is one of the very few fluoropolymers that dissolves in C02 at modest temperatures and pressures less than 300 bar. The characteristics needed to make a fluoropolymer soluble in C02 can be ascertained from Figure 7.2, which shows the difference in cloud-point curves for polyfvinylidene fluoride) (PDVF), a statistically random copoly-... 

Mandal, D., Yoon, S., Kim, K.J., 2011. Origin of piezoelectricity in an electrospun polyfvinylidene fluoride-trifluoroethylene) nanofiber web-based nanogenerator and nano-pressure sensor. Macromol. Rapid Commun. 32,831-837. 

Costa, C.M., Rodrigues, L., Sencadas, V, Silva, M., Rocha, J.G., Lanceros-Mndez, S., 2012. Effect of degree of porosity on the properties of polyfvinylidene fluoride-trifluorethylene) for Li-ion battery separators. 

Djian, D., Alloin, E, Martinet, S., Lignier, H., 2009. Macroporous polyfvinylidene fluoride) membrane as a separator for Uthium-ion batteries with high charge rate capacity. J. Power Sources 187,575-580. 

Baltd-Calleja, F. Gonzalez Arche, A., Ezquerra, T. A., Santa Cruz, C., Batalldn, F., Frick, B. and Ldpez Cabarcos, E. Structure and Properties of Ferroelectric Copolymers of Polyfvinylidene) Fluoride. Vol. 108, pp. 1-48. 

F igure 1.30. Relationship of fatigue crack growth rate per cycle in several polymers as a function of range of stress intensity factor AK, which is a measure of the range in stress concentrated at the crack tip during cyclic deformation (Hertzberg et ai, 1973). PVF, polyfvinylidene fluoride) PMMA, poly(methyl methacrylate) PC, polycarbonate PS, polystyrene. 

Du, J.R., Peldszus, S., Huck, P.M. and Feng, X. 2009. Modification of polyfvinylidene fluoride) ultrafiltration membranes with poly( vinyl alcohol) for fouling control in drinking water treatment 43 4559—4568. 

Duputell, D. and Staude, E. 1993. Heterogeneous modification of ultrafiltration membranes made from polyfvinylidene fluoride) and their characterization. 78 45-51. 

Lee, YM. and Shim, J.K. 1996. Plasma surface graft of acrylic acid onto a porous polyfvinylidene fluoride) membrane and its riboflavin permeation. 

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