Piezoelectric poly vinylidene

Figure 4.3 Piezoelectric poly(vinylidene difluoride) PVDF and its non-piezoelec-tric isomer, poly(ethylene-co-tetrafluor-oethylene) (ETFE) [6].

Piezoelectric Poly(vinylidene fluoride) in Small-Bore, Thick-Walled Tubular Form... 

Piezoelectric Poly(Vinylidene) Fluoride (PVDF) in Biomedical Ultrasound Exposimetry... 

J. P. Luongo, Far-infrared spectra of piezoelectric poly vinylidene fluoride, J. Polymer ScL A-2 70 1119 (1972)... 

Correia, D.M., Ribeiro, C., Sencadas, V., VUdngsson, L., Oliver Gasch, M., Gomez RibeUes, J.L., et al., 2016. Strategies for the development of three dimensional scaffolds from piezoelectric poly(vinylidene fluoride). Mater. Des. 92, 674—681. 

The anisotropy of piezoelectricity in oriented polymer films is quite different among polymers. The piezoelectric effect in oriented polypeptide films is greatest when elongated along a direction at 45° to the draw-axis. On the contrary, the effect is most remarkable for elongation along the draw-axis for roll-drawn poly(vinylidene fluoride) film. 

As will be shown in the theory, the electrostriction effect plays an important role in the piezoelectric effect of polymer films. Moreover, a knowledge of the complex electrostriction constant as a function of frequency reveals a new aspect of the relaxational behavior of polymers. In this review a new method for measuring complex electrostriction constant with varying frequency will be presented with some results for poly(vinylidene fluoride). 

A close correlation between the polarities of piezoelectricity and pyroelectricity was found for PVC and poly (vinylidene fluoride) (PVDF) films (Nakamura and Wada, 1971). However, it must be emphasized that the polarity of piezoelectricity is determined not only by the polarity of the charge distribution but also by that of heterogeneous strain. The origin of heterogeneous strain in the elongation of film may derive from heterogeneity in the structure of the film. 

Fig. 26. Correlation between increment of spontaneous polarization from 80° C to 15° C and piezoelectric strain constant at room temperature for /9-form polarized poly(vinylidene fluoride) films. Poling temperature = 90° C. Poling field = 700 kV/cm (Murayama, 1972)...

Fig. 28. Piezoelectric stress constant obtained from inverse piezoelectric effect and electrostriction constant of drawn and polarized poly(vinylidene fluoride) film plotted against temperature. Draw ratio = 7. Polarized at 90° C under the field of 400 kV/ctn for 3 hours. Frequency of applied voltage = 37.5 Hz. (Oshiki and Fukada, 1971) Broken line represents dielectric constant at 21.5 Hz for roll-drawn poly (vinylidene fluoride) film (Peterlin and Eiweil, 1969)...

Takashita, S. Piezoelectric effect in polarized poly(vinylidene fluoride). Japan. J. Appl. Phys. 8,960 (19 ). 

Sakurai,T. Piezoelectricity in polarized poly(vinylidene fluoride) films. Polymer J. 2,676 (1971). 

Nakamura, K., Wada,Y. Piezoelectricity, pyroelectricity, and the electro- striction constant of poly(vinylidene fluoride). J. Polymer Sci. A-2, 9, 161 (1971). 

Fig. 4. The effect of temperature on the piezoelectric strain constant, d3v for A, nylon-11 B, nylon-7 and C, poly(vinylidene...

Of greater interest in recent years have been the peculiar piezolectric properties of poly(vinylidene 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. 

The piezoelectric phenomena have been used to generate ultrasonic waves up to microwave frequencies using thin poly(vinylidene fluoride) transducers. In the audio range a new type of loudspeaker has been introduced using the transverse piezolectric effect on a mechanically biased membrane. This development has been of considerable interest to telephone engineers and scientists. 

This paper presents details of a new, low-cost, continuous process in which pellets of poly(vinylidene fluoride) (PVDF) are directly converted into piezoelectric tube. Kawai s paper in 1969 (1 ) described a batch process for making PVDF piezoelectric by stretching filmB at an elevated temperature and subsequently applying a high electric field to the electroded and heated films (thermal poling). Since then many variations of this technique have been described. Southgate in 1976 (2) demonstrated that... 

Figure 11.11 The schematic crystal structure of two forms of poly(vinylidene fluoride), PVF2, viewed down the polymer chains, shown as double triangles the electric dipoles in the chains are drawn as arrows, (a) The dipoles cancel in a centrosymmetric stmcture and the material is a nonpiezoelectric, (h) The dipoles add together in a non-centrosymmetric structure and the material is piezoelectric...

A major advance was made in 1969 when a strong piezoelectric effect was discovered in poly(vinylidene fluoride) (PVDF). The effect is much greater than for other polymers. In 1971, the pyroelectric properties of PVDF were also first reported, and as a consequence, considerable research and development has continued during the last two decades. 

Su J, Ma ZY, Scheinbeim JI, Newman BA (1995) Ferroelectric tmd piezoelectric properties of nylon ll/poly(vinylidene fluoride) bilaminate films. J Polym Sci B 33 85... 

Ferroelectric composites are alternatives to standard piezoelectric and pyroelectric ceramics such as lead zirconate titanate (PZT) and BaHOs (BT). They combine the strong ferroelectric and dielectric properties of ceramics with the easy processing and good mechanical properties of polymers. Dispersion of micrometer-sized ferroelectric particles in an electrically passive epoxy matrix was first published by Furukawa et al. [1976] and later extended to ferroelectric matrices such as poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride-co-3-fluoroethylene) (PVDF-TrFE) [Hsiang et al., 2001 Hilczer et al., 2002 Gimenes et al., 2004 Lam et al., 2005 Beloti et al., 2006]. However, the necessity of miniaturization of electronic components and... 

Piezoelectricity links the fields of electricity and acoustics. Piezoelectric materials are key components in acoustic transducers such as microphones, loudspeakers, transmitters, burglar alarms and submarine detectors. The Curie brothers [7] in 1880 first observed the phenomenon in quartz crystals. Langevin [8] in 1916 first reported the application of piezoelectrics to acoustics. He used piezoelectric quartz crystals in an ultrasonic sending and detection system - a forerunner to present day sonar systems. Subsequently, other materials with piezoelectric properties were discovered. These included the crystal Rochelle salt [9], the ceramics lead barium titanate/zirconate (pzt) and barium titanate [10] and the polymer poly(vinylidene fluoride) [11]. Other polymers such as nylon 11 [12], poly(vinyl chloride) [13] and poly (vinyl fluoride) [14] exhibit piezoelectric behavior, but to a much smaller extent. Strain constants characterize the piezoelectric response. These relate a vector quantity, the electrical field, to a tensor quantity, the mechanical stress (or strain). In this convention, the film orientation direction is denoted by 1, the width by 2 and the thickness by 3. Thus, the piezoelectric strain constant dl3 refers to a polymer film held in the orientation direction with the electrical field applied parallel to the thickness or 3 direction. The requirements for observing piezoelectricity in materials are a non-symmetric unit cell and a net dipole movement in the structure. There are 32-point groups, but only 30 of these have non-symmetric unit cells and are therefore capable of exhibiting piezoelectricity. Further, only 10 out of these twenty point groups exhibit both piezoelectricity and pyroelectricity. The piezoelectric strain constant, d, is related to the piezoelectric stress coefficient, g, by... 

He, X. Yao, K, (2006), Crystallization mechanism and piezoelectric properties of solution-derived ferroelectric poly(vinylidene fluoride) thin films. Applied Physics letter. Vol. 89, No. 11, pp. 112909-1 -112902-3, ISSN 0003-6951. 

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