Polyvinylidene fluoride electrical properties

A specific set of experiments which must be mentioned, being directly associated with the main topic of this paper, is the work of Bergman, et. al. (22) dealing with the second-order nonlinear optical properties of polyvinylidene fluoride (PVF2). Nonvanishing the second-order nonlinear electric dipole susceptibility, is expected in PVF2 since it exhibits other properties requiring noncentrosymmetric microscopic structure. These properties appear... 

More recently, modified fluoroplastics such as fluorinated ethylene/propylene copolymer, polychlorotrifluoroethylene, and polyvinylidene fluoride have been offered by DuPont, Allied Chemical, 3M, and Pennwalt respectively, to provide improved processability and mechanical strength at some sacrifice in heat-resistance, electrical properties, and chemical resistance and at prices of 3.70-7.15 these have also been finding appropriate if smaller markets. 

The unique dielectric properties and polymorphism of PVDF are the source of its high piezoelectric and pyroelectric activity.75 The relationship between ferroelectric behavior, which includes piezoelectric and pyroelectric phenomena and other electrical properties of the polymorphs of polyvinylidene fluoride, is discussed in Reference 76. 

Typical Electrical Properties of Polyvinylidene Fluoride Homopolymer... 

Polyvinylidene fluoride (PVDF) is a homopolymer of 1,1-difluoroethene with alternating CH2 and CF2 groups along the polymer chain. These groups impart a unique polarity that influences its solubility and electrical properties. The polymer has the characteristic stability of fluoropolymers when exposed to aggressive thermal, chemical, and ultraviolet conditions. 

Polyvinylidene Fluoride Thermoplastic polymer of vinylidene fluoride has good strength, proeessability, wear, fire, solvent, and creep resistance, and weatherability, but decreased dielectric properties and heat resistance. Processed by injection and transfer molding, extrusion, and powder coating. Used in electrical insulation, pipes, chemical apparatus, coatings, films, containers, and fibers. Also called PVDF. 

Polyvinylidene fluoride Good UV, nuclear, weather, and chemical resistance good electrical properties. 

Chen et al. [82] studied the mechanical and electrical properties of carbon black/ polyvinylidene fluoride-tetrafluoroethylene-propylene films cross-linked with triethylene diamine. 

KYNAR pol5n inylidene fluoride was introduced in 1960. First commercial production began in 1965. For the first five years of its life, KYNAR resin was used almost exclusively in the electrical and electronic market. In 1965, the architectural finish, KYNAR 500 , was introduced followed by first plant expansion in 1969. In 1975, KYNAR 460 was introduced for high speed wire extrusion. In 1981, the Underwriter Laboratories listed KYNAR resins for use in plenum cables that can be used without conduit. In 1983, a new homopolymer series was introduced known as the series 700 and was followed by KYNAR FLEX 2800 in 1984. To meet the demands of the growing markets, a new plant for KYNAR resins was built and placed in operation in 1985. Also that year, new coating resins, KYNAR SL and KYNAR ADS , were introduced. KYNAR polyvinylidene fluoride is a crystalline polymer that is produced by the emulsion polymerization technique. Typical properties are discussed. 

Lin M-F, Thakur VK, Tan EJ, Lee PS (201 la) Dopant induced hollow BaTi03 nanostiuctures for application in high performance capacitors. J Mater Chem 21 16500-16504 Lin M-F, Thakur VK, Tan EJ, Lee PS (201 lb) Surface functionalization of BaTi03 nanoparticles and improved electrical properties of BaTi03/polyvinylidene fluoride composite. RSC Adv 1 576-578... 

Lin M-F, Thakur VK, Tan EJ, Lee PS (2011a) Surface functionalization of BaTi03 nanoparticles and improved electrical properties of BaTi03/polyvinylidene fluoride composite. RSC Adv 1 576-578... 

Kawai s (7) pioneering work almost thirty years ago in the area of piezoelectric polymers has led to the development of strong piezoelectric activity in polyvinylidene fluoride (PVDF) and its copolymers with trifluoroethylene and tetrafluoroethylene. These semicrystalline fluoropolymers represent the state of the art in piezoelectric polymers. Research on the morphology (2-5), piezoelectric and pyroelectric properties (6-70), and applications of polyvinylidene fluoride 11-14) are widespread in the literature. More recently Scheinbeim et al. have demonstrated piezoelectric activity in a series of semicrystalline, odd numbered nylons (75-77). When examined relative to their glass transition tenq>erature, these nylons exhibit good piezoelectric properties (dai = 17 pCTN for Nylon 7) but have not been used commercially primarily due to the serious problem of moisture uptake. In order to render them piezoelectric, semicrystalline polymers must have a noncentrosynunetric crystalline phase. In the case of PVDF and nylon, these polar crystals cannot be grown from the melt. The polymer must be mechanically oriented to induce noncentrosynunetric crystals which are subsequently polarized by an electric field. In such systems the amorphous phase supports the crystalline orientation and polarization is stable up to the Curie temperature. 

A typical example for the frequency- and temperature-dependent dielectric properties of a piezoelectric polymer is given in Fig. 7 that displays the a-relaxation, related the dynamic glass transition, of a polyvinylidene fluoride (PVDF) film along with an upswing of the dielectric loss at low frequencies due to electrical conduction. 

Poly(3HB) and poly(3HB-co-3HV) are piezoelectric materials, whereas the piezoelectric properties of other PHAs have not been investigated (Steinbuchel 1996). The piezoelectric materials produce electric charges on parts of their surface when mechanical pressure is applied to the crystalline material, and an electric current will result from the charges if the crystal is short circuited. Conversely, application of a voltage between certain faces of the material produces a mechanical distortion (a deformation) of the material. Piezoelectric materials have important applications in electromechanical transducers, such as microphones. In medicine, chemically synthesized piezoelectric polymers such as polyvinylidene fluoride stimulated bone growth. The piezoelectric property of poly(3HB) may be important for some medical applications (Steinbuchel 1996). 

Certain polymers, such as polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), possess special properties in the film form, caileApiezoelectricity and pyroelectricity. Piezoelectricity is electric polarization of a film produced by mechanical strain in some crystals. The polarization is proportional to the amount of strain and changes sign with it. The reverse is true and an electrical polarization induces a mechanical strain in piezoelectric sensors. Pyroelectricity is electric polarization of a film induced by thermal absorption in some polymer crystals. The induced polarization is proportional to the level of thermal change. These properties can be used in the manufacture of transducers, microphones, loudspeakers, pressure gauges, pickup heads, hydrophones, motion sensors, and other devices from biaxially oriented PVDF films. Table 13.37 gives the properties of a piezoelectric film of polyvinylidene fluoride. 

---