Download or read book Ferroelectric and Piezoelectric Properties of a Quenched Poly Vinylidene Fluoride Trifluoroethylene Copolymer written by and published by . This book was released on 1996 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ferroelectric and piezoelectric properties of melt-quenched unoriented poly(vinylidene fluoride-trifluoroethylene) (73:27) copolymer films as a function of the number of poling cycles have been studied. The investigation revealed that quenched films exhibit a decrease in D-E hysteresis behavior as the number of poling cycles increases when the samples are poled at room temperature. Corresponding decreases in remanent polarization, Pr, as well as small increases in the coercive field, Ec, were observed as the material was subjected to successive poling cycles. The piezoelectric coefficients, d31 and e31, also decreased as the number of poling cycles increased. In addition, a clear reduction in the 'apparent' Curie transition temperature between unpoled and poled material was observed. Preliminary evidence indicates that films quenched below Tc do not form a stable ferroelectric crystal phase as previously believed.
Download or read book Ferroelectric Properties and Polarization Switching Kinetic of Poly vinylidene Fluoride trifluoroethylene Copolymer written by Duo Mao and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Piezoelectric Properties and Temperature Stability of Poly Vinylidene Fluoride Trifluoroethylene Copolymers written by G. M. Stack and published by . This book was released on 1986 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Piezoelectric measurements were made on several copolymers of vinylidene fluoride and trifluoroethylene having a vinylidene fluoride concentration in the range of 65 to 75%. The hydrostatic g constant showed only a slight dependence on pressure, and pressures up to 35 MPa caused no apparent loss of the piezoelectric activity. A significant increase in the value of the hydrostatic g constant occurred with an increase in temperature. Anomalous results obtained upon cooling below room temperature may be attributed to the glass transition temperature of the trifluoroethylene comonomer. Temperature aging studies were performed at high temperatures using films of these copolymers. A significant loss of piezoelectric activity occurred after long time exposure. Isothermal studies at various aging temperatures revealed that this decay continued over a long time span. The aging behaviour characteristically followed a linear dependence on the logarithm of aging time. Keywords: Piezoelectric measurements; Vinylidene fluoride copolymers; Temperature stability.
Download or read book Investigations of the Ferroelectric and Piezoelectric Behavior of Poly vinylidene Fluoride trifluoroethylene Random Copolymers written by Michael C. Christie and published by . This book was released on 1999 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ferroelectric Polymers written by E. Fukada and published by CRC Press. This book was released on 1989 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains four papers commencing with an introduction to early studies in piezoelectricity, pyroelectricity and ferroelectricity in polymers. Other topics discussed include - ferroelectric properties of fluoride copolymers; structural phase transition in ferroelectric fluorine polymers; and pressure effect on phase transition in ferroelectric polymers .
Download or read book Electrostrictive and Ferroelectric Properties of Poly vinylidene Fluoride hexafluroropropylene Copolymer and Its Blends with Poly vinylidene Fluoride trifluoroethylene Copolymer written by Adriana Schirokauer and published by . This book was released on 2002 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Piezoelectric and Pyroelectric Properties of an Oriented Vinylidene Fluoride trifluoroethylene Copolymer written by John Anthony Day and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ferroelectric Polymers written by Hari Singh Nalwa and published by CRC Press. This book was released on 1995-06-20 with total page 913 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work covers the chemistry and physics of polymeric materials and their uses in the fields of electronics, photonics, and biomedical engineering. It discusses the relationship between polymeric supermolecular structures and ferroelectric, piezoelectric and pyroelectric properties.
Download or read book Electrets written by Gerhard M. Sessler and published by Springer Science & Business Media. This book was released on 2005-08-01 with total page 463 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ferroelectric and Piezoelectric Properties of Nylon 11 Poly Vinylidene Fluoride Bilaminate Films written by and published by . This book was released on 1994 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ferroelectric and piezoelectric properties of a new class of polymer ferroelectric and piezoelectric materials, nylon 11/polyvinyi lidene fluoride (PVF2) bilaminate films, prepared by a co-melt-pressing method, is presented. The bilaminate films exhibit typical ferroelectric D-E hysteresis behavior with a remanent polarization, P(sub r), of about 75 mC/sq m, which is higher than the value of 52 mC/sq m observed for PVF2 or nylon 11 films measured under the same conditions. The coercive field, E(sub c), of the bilaminate films is approx. 78 Mv/m which is higher than that of either PVF2 or nylon 11 films. Measurements of the temperature dependence of the piezoelectric strain coefficient, d31, and the piezoelectric stress coefficient, e31, were also carried out. The bilaminate films exhibit a piezoelectric strain coefficient, d31, of 41 pC/N at room temperature, which is significantly higher than the PVF2 films (25 pC/N) and the nylon 11 films (3.1 pC/N). jg.
Download or read book Ferroelectric and Piezoelectric Properties of Odd Numbered Nylons written by and published by . This book was released on 1992 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent discoveries in our laboratory of a new class of ferroelectric polymers--the odd-numbered nylons--led to another important discovery: a mechanism for the stabilization of the remanent polarization in these materials to their crystalline melting point. As the piezoelectric response of ferroelectric polymers is as stable as their remanent polarization, we have produced a set of high temperature stable piezoelectric polymers which can easily operate in a temperature range up to approximately 250 deg C. in addition, vie have now begun to examine new types of piezoelectric polymer films consisting of co-electroprocessed layers of odd-numbered nylon film and poly(vinylidene fluoride) PVF film, which are shown to exhibit a significantly enhanced response, compared to that of either component. Enhanced response is also observed for blended powders of PVF 2 and a copolymer of vinylidene fluoride and tri-fluoroethylene.
Download or read book Novel Ferroelectric Behavior in Poly vinylidene Fluoride co trifluoroethylene based Random Copolymers written by Lianyun Yang and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: High dielectric constant and low loss polymer dielectrics are desired for applications such as energy storage, electrocaloric cooling, and electrostrictive actuation. Several types of polarizations can be utilized to enhance dielectric constant of polymer dielectrics. Polymers with permanent dipoles can be good candidates to achieve high dielectric constant and low loss properties because of their dipolar polarization. There are several situations of dipolar polarization for polar polymers with permanent dipoles, which depend on different dipole/domain structures. Our work focuses on the novel ferroelectric behavior of ferroelectric polymers. The mechanism for novel ferroelectric behavior can be explained by the crystal pinning effect from crystal isomorphism. The physical pinning effect in P(VDF-TrFE-CFE) is weak and double hysteresis loop (DHL) is thus observed. The chemical pinning effect in e-beam P(VDF-TrFE) or P(VDF-TrFE-CTFE) is strong and only single hysteresis loop (SHL) is observed. Besides P(VDF-TrFE-CTFE), DHLs can also be achieved in P(VDF-TrFE-TrFE)-g-PS graft copolymer by the nanoconfined effect. Crystal orientation and temperature effects on the DHL behavior of the graft copolymer were studied. Clear dielectric, rather than ferroelectric, behavior is observed from the non-oriented graft polymer sample. But stable DHLs are observed for the oriented films up to 75 C. Above 100 C, huge broadening of the D-E loops shows up due to the electrical conduction and ion migrational losses. The electrical conduction loss plays an important role on the insulation property of dielectric polymers, especially at high temperatures and under high electric fields. As an example, a commercial biaxially oriented PVDF (BOPVDF) film was selected to study the electrical conduction under different electric poling conditions. The dipoles from either amorphous or crystalline phase do not have much influence on the electronic conduction. The electronic conductivity for the BOPVDF film is low below 25 C. Above 25 C, the electronic conductivity first increases, then decreases upon increasing the poling fields. These changes can be attributed to the effect from polarized ions. Above 75 C, electronic conductivity substantially increase due to injected space charges. Meanwhile, PVDF starts to undergo electrochemical reactions, emitting HF gas which can corrode metal electrodes.
Download or read book Flexoelectric and Ferroelectric Properties of Quenched Polyvinylidene Fluoride PVDF Homopolymer Films written by Sankar Thiruvannamalai and published by . This book was released on 2010 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flexoelectric and ferroelectric properties of quenched polyvinylidene fluoride (PVDF) homopolymer films have been investigated in this thesis. It is well known that PVDF homopolymer mainly has three phase structures, alpha phase (TGTG'), beta phase (TTTT), and gamma phase (TTTGTTTG'), depending on the chain conformations as the trans (T) or the gauche (G) linkages. However, the quenched PVDF homopolymer has different molecular chain conformations, which may render some unique mechanical and electric properties. Quenching is a mechanical process in which PVDF homopolymer is strengthened and hardened. This is done by heating PVDF solution at a certain temperature, where the polymerization cannot be formed, then rapidly cooling the polymer; in annealing process, only in certain local microscopic areas, polymerization can occur to let PVDF monomer molecules aggregate together to form the alpha, beta, and gamma phases.^So the regions between those areas in the polymer have amorphous structures. Thus, the piezoelectric behavior of the quenched PVDF homopolymer might be altered since only beta phase and gamma phase in PVDF possess piezoelectric responses and the volume, in which both beta phase and gamma phase exist, in the quenched polymer is reduced. However, whether the direct flexoelectric effect is influenced or not in the quenched PVDF homopolymer is still unknown. This is because the direct flexoelectric effect can exist in polymers of any phase; the inhomogeneous deformation can break the inversion symmetry and induce electric polarization even in non-piezoelectric phase. In our experimental studies, the quenched PVDF homopolymer films were initially synthesized using solution polymerization process and then were quenched in ice-water. We further characterized our samples by using X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM).^The flexoelectric coefficients of those polymer films were then measured. Both the enhanced direct flexoelectric effect and the ferroelectric-like behavior were observed in the quenched polymer films. Our studies have shown that both the effect and the behavior largely depend on the molecular chain configurations of the quenched PVDF films. Our experimental results also demonstrate that the ferroelectric-like behavior in the quenched PVDF film might be induced by its spatially distributed space electric charges. The measured flexoelectric coefficient (mu13) may also give us valuable information about how aging phenomena would be induced in polymer films.
Download or read book New Properties and Applications of Polyvinylidene Based Ferroelectric Polymer written by J.L. Wang and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: There are different kinds of novel properties and applications of polyvinylidene difluoride (PVDF)-based ferroelectric polymer films. Several issues associated with the structure, properties, and applications of PVDF-based ferroelectric polymer films are discussed. The main achievements of the research include high electric tunability of relaxor ferroelectric Langmuir-Blodgett (LB) terpolymer films, the creep process of the domain switching in poly(vinylidene fluoride-trifluoroethylene) ferroelectric thin films, transition from relaxor to ferroelectric-like phase in poly(vinylidene fluoride-trifluoroethylene -chlorofluoroethylene) terpolymer ultrathin films, abnormal polarization switching of relaxor terpolymer films at low temperatures, huge electrocaloric effect in LB ferroelectric polymer thin films, self-polarization in ultrathin LB polymer films, enhanced dielectric and ferroelectric properties in artificial polymer multilayers, and transition of polarization switching from extrinsic to intrinsic in ultrathin PVDF homopolymer films.
Download or read book Water Interactions with the Crystalline Ferroelectric Copolymer Poly vinylidene Fluoride with Trifluoroethylene written by Luis G. Rosa and published by . This book was released on 2005 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Investigation on Ferroelectric and Flexoelectric Properties of Poly vinylidenefluoride hexafluoropropylene PVDF HFP Copolymer Films written by Ho Joon Lee and published by . This book was released on 2010 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: The electric polarization induced by the non-uniform deformation, i.e. the direct flexoelectric effect, in poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) has been investigated. The ferroelectric properties of PVDF-HFP copolymer films were measured. The primary goal of the research in this thesis is to understand the properties of both ferroelectricity and flexoelectricity of PVDF-HFP copolymer films under different circumstances. It is well known that PVDF homo polymer mainly has three phase structures, α phase (TGTG'), β phase (TTTT), and γ phase (TTTGTTTG'), depending on the chain conformations as the trans (T) or the gauche (G) linkages. Only β phase and γ phase possess piezoelectric responses. The direct flexoelectric effect can exist in any phase. This is because the inhomogeneous deformation can break the inversion symmetry and induce electric polarization even in non-piezoelectric crystalline materials.^However, in PVDF-HFP copolymer, the molecular chain conformations of PVDF are modified by HFP monomers. Although the mixture of two polymers can be regarded as a random amorphous structure, their molecular chain conformations may splay to different directions if a non-uniform deformation is applied to them. Therefore both ferroelectric and flexoelectric properties of PVDF-HFP copolymers might be significantly different from that of PVDF homo polymers. In our experimental studies, the unaligned PVDF-HFP copolymer films were initially synthesized by using the solution polymerization process and then characterized via X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The flexoelectric coefficients of those polymer films were then measured. Both the enhanced direct flexoelectric effect and the ferroelectric-like behavior were observed in the polymer films.^However, the flexoelectric coefficient of PVDF-HFP copolymers we measured is almost 50% smaller than that of the unaligned PVDF homo films. The experimental results also demonstrate that the ferroelectric-like behavior in PVDF-HFP copolymers under different conditions might be induced by their spatially distributed space electric charges. The measured flexoelectric coefficient (μ13) and the piezoelectric coefficient (d13) can also give us valuable information about the property degradation, or aging phenomena, in polymer films and the related polymer devices.
Download or read book Ferroelectric Properties of Poly vinylidene Fluoridetetrafluoroethylene written by J. C. Hicks and published by . This book was released on 1978 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report investigates the electrical properties of a copolymer of vinylidene fluoride and tetrafluoroethylene. To accomplish this, the charge induced on the surface of the copolymer was measured as a function of the electric field at room temperature, the dielectric constant was measured as a function of temperature, and the piezoelectric coefficients of films of various thicknesses were measured as a function of the poling field. All results suggest that this copolymer is ferroelectric and that poling aligns the dipoles in the beta crystal phase of the material. (Author, modified-PL).
