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 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 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 Effects of Configurational Changes on Molecular Dynamics in Polyvinylidene Fluoride and Poly vinylidene Fluoride trifluoroethylene Ferroelectric Polymers written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, we present a comparative study of proton dynamics in unpoled non-ferroelectric polymer polyvinylidene fluoride (PVDF) and in its trifluoroethylene containing ferroelectric copolymer (with 70/30 molar proportion), using quasi-elastic neutron scattering. The neutron data reveal the existence of two distinct types of molecular motions in the temperature range investigated. Moreover, the slower motion, which is characterized in details here, is ascribed to protons jump diffusion along the polymeric carbon chains, while the faster motion could be attributed to localized rotational motion of methylene groups. At temperatures below the Curie point (T-c similar to 385 K) of the composite polymer, the slower diffusive mode experiences longer relaxation times in the ferroelectric blend than in the bare PVDF, although the net corresponding diffusion coefficient remains comparatively the same in both polymers with characteristic activation energy of E-A approximate to 27-33 kJ/mol. This arises because of a temperature dependent jump length r(0), which we observe to be effectively longer in the copolymer, possibly due to the formation of ordered ferroelectric domains below Tc. Above Tc, there is no appreciable difference in r(0) between the two systems. Our observation directly relates the known dependence of Tc on molar ratio to changes in r(0), providing fundamental insight into the ferroelectric properties of PVDF-based copolymers.
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 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 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 The Structure of Ferroelectric Polyvinylidene Fluoride trifluoroethylene PVDF TrFE Copolymer Langmuir Blodgett Films written by Mengjun Bai and published by . This book was released on 2002 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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).
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 Understanding the Composition structure property Relationships and Enhancing the Electromechanical Responses in Ferroelectric Polymers written by Zhubing Han and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Poly(vinylidene fluoride) (PVDF)-based ferroelectric polymers enable a wide range of advanced applications with new functionalities and structure designs due to their high electroactivity, intrinsic flexibility and biocompatibility. One unique feature of these polymers is that their dielectric, ferroelectric and electromechanical properties can be modulated by varying their chemical composition and the processing conditions. Despite the progress over the last decades, a more comprehensive understanding on the composition--structure--property relationships in PVDF-based ferroelectric polymers is still needed to achieve rational design of new materials with enhanced performance. The scope of this dissertation aims to understand the influence of monomer defects on the structures and ferroelectric properties of PVDF-based terpolymers, and to enhance their electromechanical performance enabled by the rational design of new polymer structures and compositions. After a general background introduction, the dissertation starts with two chapters discussing the effect of two different comonomers as chain defects on the structures and ferroelectric properties of the corresponding terpolymers. Chapter 2 reveals that the incorporation of bulky 2-chloro-1,1-difluoroethylene (CDFE) can gradually convert the ferroelectric P(VDF-TrFE) (TrFE: trifluoroethylene) into a relaxor ferroelectric terpolymer as confirmed by the dielectric and structural characterizations. The CDFE comonomer serves as an effective chain defect to destabilize the ferroelectric domain by introducing the gauche conformation. The P(VDF-TrFE-CDFE) with 3.8 mol% CDFE exhibits typically relaxor ferroelectric behaviors such as strong frequency-dependence of dielectric properties, broad and diffuse ferroelectric phase transition, and weak remanent polarization. Chapter 3 systematically investigates the effect of another comonomer defect, vinyl fluoride (VF), which has a smaller size than VDF. It is found that VF plays an opposite role compared with the bulky chlorinated comonomers. Increasing molar content of VF leads to an increase in the Curie temperature and the coercive field of the terpolymers. Structural characterizations and simulations evidences confirm that the all-trans conformation remain energetically more favored than the gauche conformation regardless of the VF content. The results stress the vital role of comonomer structure and size in modulating the structures and properties of the ferroelectric polymers. The next two chapters focus on improving the electromechanical performance of the PVDF-based polymers. In Chapter 4, a series P(VDF-TrFE-CTFE) (CTFE: chlorotrifluoroethylene) with systematic composition variations have been synthesized. Structural characterizations show that the terpolymers with 1.7 to 5.0 mol% CTFE exhibit a mixture and competition of the normal ferroelectric and relaxor ferroelectric phases as a result of the incorporation of CTFE. Specifically, a maximum longitudinal piezoelectric coefficient (d33) of -55.4 pm/V has been observed in P(VDF-TrFE-CTFE) 64.5/33.1/2.4 mol%, corresponding to an 85% improvement compared with the commercial benchmark P(VDF-TrFE) 65/35 mol%. This strategy can potentially be expanded to other polymer systems to improve the piezoelectric response. Chapter 5 aims to enhance the low-electric-field electrostrictive strain in relaxor ferroelectric polymers. The small electrostrain of current relaxor ferroelectric P(VDF-TrFE-CFE) (CFE: 1-chloro-1-fluoroethylene) and P(VDF-TrFE-CTFE) terpolymers at low electric field impedes their usefulness in actuating devices. In situ structural characterizations under the electric field reveal that the electrostrictive strain originates from the field-induced phase transition in P(VDF-TrFE-CFE) and the lattice compression in P(VDF-TrFE-CTFE). Inspired by the distinct functions of CFE and CTFE, a series of P(VDF-TrFE-CFE-CTFE) tetrapolymers have been synthesized, which exhibit significant enhancement of electrostrictive strain at both low and high electric fields due to the synergistic effect of CFE and CTFE. These results provide new insight into the origin of electrostriction in the relaxor ferroelectric polymers, and the tetrapolymers in this study can potentially be used to prototype soft actuators. It is anticipated that the materials, methodologies and results developed in this dissertation will not only provide new insights and understandings on the structure-property relationship in ferroelectric polymers, but also stimulate future work to further enhance the performance in these materials in order to meet the material requirement for practical applications.
Download or read book Characterization of the Mechanical and Ferraelectric Properties of Plasticized Poly vinylidene Fluoride and Poly vinylidene Fluoride trifluoroethylene Films written by David L. Winsor and published by . This book was released on 1996 with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Confined Ferroelectric Properties in Poly vinylidene Fluoride PVDF based Random Copolymers and Graft Copolymers for Electric Energy Storage Applications written by Fangxiao Guan and published by . This book was released on 2010 with total page 0 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 The Role of High Pressure in the Study and Applications of the Ferroelectric Polymer Polyvinylidene Fluoride and Its Copolymers written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Effects of frequency, temperature and hydrostatic pressure on dielectric properties, molecular relaxations, and phase transitions of PVDF and a copolymer with 30 mol % trifluoroethylene are discussed. Pressure causes large slowing down of the [beta] molecular relaxations as well as large increases in the, ferroelectric transition temperatures and melting points, but the magnitudes of the effects are different for the different transitions. These effects can be understood in terms of pressure-induced hindrance of the molecular motions and/or reorientations. A unique application of these polymers as time-resolved dynamic stress gauges based on PVDF studies under very high pressure shock compression is discussed.
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 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.
