Polymer 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. 

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

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.

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],... 

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-... 

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. 

The inability to process PTFE by conventional thermoplastics techniques has nevertheless led to an extensive search for a melt-processable polymer but with similar chemical, electrical, non-stick and low-friction properties. This has resulted in several useful materials being marketed, including tetrafluoro-ethylene-hexafluoropropylene copolymer, polyfvinylidene fluoride) (Figure 13.1(d)), and, most promisingly, the copolymer of tetrafluoroethylene and perfluoropropyl vinyl ether. Other fluorine-containing plastics include poly(vinyl fluoride) and polymers and copolymers based on ClFE. 

Figure 7.56. Differential scanning calorimetry (DSC). Shown are (a) schematic of the heat-flux sample chamber (b) an example of a DSC thermogram, showing endothermic and exothermic events (c) DSC thermogram of a polyfvinylidene fluoride)-ethyl acetoacetate polymer-solvent system, showing two melting events for the polymer due to its intermolecular interactions with solvent molecules. The inset shows a comparison between the pure polymer (b) and the polymer-solvent (a). Reproduced with permission from Dasgupta, D. Malik, S. Thierry, A. Guenet, J. M. Nandi, A. K. Macromolecules 2006,59,6110.

TAZ Tazaki, M., Wada, R., Okabe, M., and Orrrrrra, T., Inverse gas chrorrtatographic observation of thermodynamic interaction between polyfvinylidene fluoride) arrd orgarric solvents, Polym. Bull, 44, 93,2000. 

N. Murayama, Persistent polarization In polyfvinylidene fluoride). L Surface charges and piezoelectricity of poly(vinylidenc fluori ) Ihermoelectrets, J. Polymer Sci A-2 13S29 (1975). 

SI M. Latour, Infra-red analysis of polyfvinylidene fluoride) thennoelectrets. Polymer l8-.Zn (1977). 

The symmetry of CL, bolds for the pokd composite films consisting of piezoelectric ceramk powders and polymers. When dongaled films ot polar polymer ate poled, the symmetry of C> appears. The 3 axes for and Ci, ate in the directioo of poling. In 1969, Kawai first discovered large tensile piezoelectricity in elongated and poled films of polyfvinylidene fluoride) (11]. 

Whereas ferroelectridty in polymers of the polyfvinylidene fluoride) (PVDF) type b induced by stretching and poling of polymers films and b not chaiacteristk for undisturbed samples, spontaneous polarization appears in liquid crystalline polymers with intrinsic lower symmetry Cj. 

Present researdi on physical properties, performance, and passible applications of electroactive polymers has oonceatraled < cooducting potymers because of their peculiar electrical properties, but the interest in polymers originally arose firom the rlieleciric ones. The strong piezoelectric effect in polyfvinylidene fluoride) (PVDF or PVFi) poled under high electric field was observed the first time by Kawai (1) in 1969, while its pyro-... 

K. Nakamura and Y. Wula, Piezoelectricity, pyroelectricity, arul the ekctramrictian anslant of polyfvinylidene fluoride). J. Polymer SU A-l 9 161 (1971). 

Poly(vinyUdeoe fluoride) provides the best example of recent advances that have been made in the understanding and iplications of a siiigle organic ferroelecttic polymer. The devehipmenis in polyfvinylidene fluoride), its copolymets, and Mends as ferroelectric... 

The resistance of polyfvinylidene fluoride) to solvents and chemicals is generally good but inferior to that of polytetrafluoroethylene and polychloro-trifluoroethylene. Some highly polar solvents such as dimethylacetamide dissolve the polymer at elevated temperature whilst organic amines cause discoloration and embrittlement. Fuming sulphuric acid leads to sulphon-ation. 

Hasegawa, R., Y. Takahashi, Y. Chatani, and H. Tadokoro. 1972. Crystal Structures of Three Crystalline Forms of PolyfVinylidene Fluoride). Polymer Journal 3(5) 600-610. doi 10.1295/poly mj.3.600. 

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