Dielectric Behavior in an Oriented β-PVDF Film and Chain Reorientation Upon Transverse Mechanical Deformation

Lanceros‐Méndez, S.; Moreira, M. V. B.; Mano, João F.; Schmidt, V. Hugo; Bohannan, Gary W.

doi:10.1080/00150190211756

Cited by 42 publications

(52 citation statements)

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“…Grains are stressed and this stress of grains may contribute to the macroscopic properties of the sample. The surface roughness in big area image is also similar as the first one (Figure 1 These results corroborate the previously obtained [5,6,7] that indicated a chain reorientation towards the stretch direction when the sample is subjected to transversal stretching. The chain reorientation is accompanied by changes in the domain configuration, as can be observed in the piezo-response images.…”

Section: Resultssupporting

confidence: 81%

“…In this investigation, we have extended previous investigations on the dependence of the different properties of β-PVDF upon a transversal deformation [5,6,7]. The differences in the topological and domain morphologies have been investigated by scanning force microscopy in a piezo-response mode and correlated with previous results.…”

Section: Introductionmentioning

confidence: 50%

“…Previous FTIR experiments showed a polarisation switching when the material was subjected to tensile stress perpendicular to the draw direction [5,6]. This switching occurs progressively within this region [6] and is accompanied by a decrease in the degree of crystallinity with no changes in the crystalline lamellae thickness [6].…”

Section: Discussionmentioning

confidence: 99%

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Electrical and Microstructural Changes of β-PVDF under Uniaxial Stress Studied by Scanning Force Microscopy

Nunes

Sencadas

et al. 2006

MSF

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Abstract. Chain reorientation may be induced in polyvinylidene fluoride (PVDF) in its β-phase by applying a deformation perpendicular to the pre-oriented polymeric chains. This reorientation begins right after the yielding point and seems to be completed when the stress-strain curve stabilizes. As the deformation process plays an important role in the processing and optimisation properties of the material for practical applications, different deformation stress was applied to the PVDF lamellas and their topographic change and piezoelectric response were studied by means of scanning force microscopy in a piezo-response mode. The experimental results confirm the previously observed chain reorientation that occurs right after the yielding point and that is completed when the yielding region is passed. This reorientation is accompanied by a stretching of the granular structures observed in the topographical images and variations in the domain response. The observed results help to explain the variations in the macroscopic response of the material.

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Section: Resultssupporting

confidence: 81%

Section: Introductionmentioning

confidence: 50%

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Electrical and Microstructural Changes of β-PVDF under Uniaxial Stress Studied by Scanning Force Microscopy

Nunes

Sencadas

et al. 2006

MSF

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“…The dependence of these bands with the degree of crystallinity and/or external fields such as strain [8][9][10] or temperature [11] allows to monitor possible variations of the chain conformations, orientations and the amount of and phases of the material under the effect of these external fields.…”

Section: Experimental Results: Infrared Spectroscopymentioning

confidence: 99%

“…The vibrational spectrum of -PVDF has been thoroughly investigated and several absorption bands characteristic of the different bonds, the -and -phases and the head-to-head and tail-totail defects of the polymer have been identified [8][9][10][11]. In particular, vibrational bands at 530 cm -1 (CF 2 bending), 615 and 766 cm -1 (CF 2 bending and skeletal bending) and 795 cm -1 (CH 2 rocking) are identified with the -phase.…”

Section: Experimental Results: Infrared Spectroscopymentioning

confidence: 99%

Atomistic modelling of processes involved in poling of PVDF

Ramos

Correia

Lanceros‐Méndez

2005

Computational Materials Science

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Poling processes play an important role in the design and preparation of many ferroelectric materials for practical uses in the field of sensors and actuators. Particularly, the processing of piezoelectric β-poly(vinylidene fluoride) (β-PVDF) involves mechanical stretching in order to transform the extruded α-phase into the β-phase and poling of this later material in order to optimise the piezoelectric response. This poling process affects the orientation of the dipolar moments of the β-chains and improves the α to β transformation.Poling processes in general and in PVDF in particular are still quite empirical because a firm understanding of the physical processes involved in poling has not been fully established.In the present work we use a self-consistent quantum molecular dynamics method to study the effect of the electric field on both α and β chains of PVDF. The orientation of the dipolar moments in each chain as a function of an electric field and the accompanying structural modifications due to these reorientations will be the main parameters discussed.The theoretical results will be used to better understand the changes at a molecular level due to the poling process, as observed in FTIR experiments, performed in poled and non-poled β-PVDF from the same batch.

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Piezoelectric coaxial filaments produced by coextrusion of poly(vinylidene fluoride) and electrically conductive inner and outer layers

Martins

Azevedo

Rocha

et al. 2014

J of Applied Polymer Sci

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The development of new thermoplastic polymer-based piezoelectric sensors with filament geometry is described. These filaments are appropriate for integration into textiles and provide new possibilities in the design and development of low-cost flexible sensors produced at high rates. The developed three-layered piezoelectric monofilaments have been produced by coextrusion using poly(vinylidene fluoride) and two different polypropylene-based electrically conductive polymers. Filaments with about 800-mm diameter, producing electrical signals proportional to the mechanical deformation applied, were obtained. The signal output has been found adequate for straightforward use with conventional piezoelectric signal conditioning systems. One of the conductive polymers tested allowed better filament geometry and process stability. This article describes the coextrusion production process and the results obtained in the electromechanical tests performed.

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Dielectric Behavior in an Oriented β-PVDF Film and Chain Reorientation Upon Transverse Mechanical Deformation

Cited by 42 publications

References 0 publications

Electrical and Microstructural Changes of β-PVDF under Uniaxial Stress Studied by Scanning Force Microscopy

Electrical and Microstructural Changes of β-PVDF under Uniaxial Stress Studied by Scanning Force Microscopy

Atomistic modelling of processes involved in poling of PVDF

Piezoelectric coaxial filaments produced by coextrusion of poly(vinylidene fluoride) and electrically conductive inner and outer layers

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