Piezo-electric polymers

Piezo-electric polymers are often materials like the p form of poly(vinylidene fluoride) in which the unit cell has a residual dipole moment. 

Atomic-force microscopy (AFM) is a technique that examines the surface topography of polymer samples. The probe moves across the surface and a piezo-electric detector can... 

It is worth mentioning that some side-chain liquid crystal polymers and liquid-crystalline networks (M = Cu, Zn, Co, Ni, Pb) have also been prepared, usually preserving the properties of the monomeric discotic units. They may find some interesting applications in the field of onedimensional conductors as well as applications using flexo- and piezo-electricity. 

The newest market for KYNAR resins is perhaps the most exciting and most challenging. This is the KYNAR Piezo Film. By definition, a piezo electric material is one that can change polarization in response to mechanical stress. The CH - CF repeat unit was found to exhibit the strongest piezo electric and pyro electric activity of all known polymers. This property was first reported in 1969 based on experiments using KYNAR PVDF. Since that time the piezo and pyro electric properties of PVDF have been the subject of many publications. 

Motion is generated hy the piezo-electric effect in certain crystalline materials (for instance Quartz), ceramics such as PZT - Pb(ZrTi)03, and polymers (Polyvinyli-dene fluoride - PVDF). In addition, thin films with piezo-electric properties such as Aluminum Nitride (AIN)... 

The present account is not intended to be comprehensive. Data which are regarded as representative of the dielectric behaviour of amorphous and partially crystalline polymers will be discussed and the structural and molecular factors invdved will be examined in some detail. A brief account will also be given of the relevance of dielectric relaxation behaviour to topics of current interest such as piezo-electrical behaviour of polymers. This acccxint attempts to build on the many earlier accounts (McCrum et d., 1967 Ishida, 1969 Hedvig, 1977 Baird, 1973 Wada, 1977 Karasz, 1972 Williams and Watts, 1971 a Van Turnhout, 1975,1978 WiUiams and Crossley, 1978 Heijboer, 1972) and is a personal assessment by the author of our current understanding of the factors which lead to multiple dielectric relaxation processes in solid polymers. 

Fumkawa T, Seo N (1990) Electrostriction as the origin of piezo-electricity in ferroelectric polymers. Jpn J Appl Phys 29(4) 675... 

K. H. Hall, Jr., R. J. Chou, J. CMcu. O. R. Hughes, J. Schctiibeun, and B. Newman, Piezo-electric activity in films of poly(l-bicyclob tanccsiboajlTik), Polymer Bull 77 135 (1987). 

Key Words Smart materials, piezo electric, electrrostrictive, magnetostrictive, integrated polymer systems... 

Pyro- and Piezoelectric Properties The electric field application on a ferroelectric nanoceramic/polymer composite creates a macroscopic polarization in the sample, responsible for the piezo- and pyroelectricity of the composite. It is possible to induce ferroelectric behavior in an inert matrix [Huang et al., 2004] or to improve the piezo-and pyroelectricity of polymers. Lam and Chan [2005] studied the influence of lead magnesium niobate-lead titanate (PMN-PT) particles on the ferroelectric properties of a PVDF-TrFE matrix. The piezoelectric and pyroelectric coefficients were measured in the electrical field direction. The Curie point of PVDF-TrFE and PMN-PT is around 105 and 120°C, respectively. Different polarization procedures are possible. As the signs of piezoelectric coefficients of ceramic and copolymer are opposite, the poling conditions modify the piezoelectric properties of the sample. In all cases, the increase in the longitudinal piezoelectric strain coefficient, 33, with ceramic phase poled) at < / = 0.4, the piezoelectric coefficient increases up to 15 pC/N. The decrease in da for parallel polarization is due primarily to the increase in piezoelectric activity of the ceramic phase with the volume fraction of PMN-PT. The maximum piezoelectric coefficient was obtained for antiparallel polarization, and at < / = 0.4 of PMN-PT, it reached 30pC/N. 

Poly(vinylidene fluoride) (PVDF) is a semicrystalline engineering polymer with very good resistance to chemicals, oxidation, and UV radiation (J. H. Yen, 2006). PVDF is known for its polymorphism crystalline structure and complicated microstructure. It is one of the most widely studied polymers due to its non-linearity, piezo- and pyro-electricity (L. T. Vo, 2007 K. Pramoda, 2005). PVDF can crystallize in at least five well-known crystalline phases (E. Giannetti, 2001, A. Lovinger, 1982 N. S. Nalwa, 1995) ... 

Althou a study of the piezo- and pyro-electricity of a polymer can provide valuable information bearing on polymer morphology and properties, this review will concentrate on the applications of these materials with particular reference to PVDF. For a fuller discussion of the baac theory the reader is directed to the excellent reviews by Hayakawa and Wada ... 

Piezo/pyroelectric composite (inorganic ferroelectric particles in polymer matrix) Ions in crystalline particles form ionic dipoles upon symmetry breaking Ionic dipoles deform/ rotate with mechanical (electrical) stress Ferroelectric matrix polymer may compensate piezo-or pyroelectric effect... 

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