scholarly journals Influence of molecular weight on dielectric properties and piezoelectric constant of poly(vinylidene fluoride) membranes obtained by electrospinning

Polimery ◽  
2021 ◽  
Vol 66 (10) ◽  
pp. 532
Author(s):  
Aminatul Sobirah Zahari ◽  
Muhammad Hafiz Mazwir ◽  
Izan Izwan Misnon
Keyword(s):  
Molecular Weight ◽  
Dielectric Properties ◽  
Vinylidene Fluoride ◽  
Electrochemical Impedance ◽  
Piezoelectric Constant ◽  
Phase Content ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Poly Vinylidene Fluoride

A significant influence of the molecular weight on the dielectric properties and piezoelectric constant of poly(vinylidene fluoride) (PVDF) membranes obtained by electrospinning was demonstrated. Electrochemical impedance spectroscopy and d33 meter were used to evaluate dielectric properties and piezoelectric constant respectively. The presence of the β-phase was determined by Fourier transform infrared spectroscopy (FTIR) and X-Ray diffraction (XRD). The membranes with the lowest molecular weight (180,000 g/mol) possessed the best dielectric properties. They also had the highest piezoelectric constant (21 pC/N) and dielectric constant (2.9 at 50 Hz) as well as the highest β-phase content (80.25%).

Stretching Induced Crystalline-Phase Transition in Energy-Conversion Poly(Vinylidene Fluoride) (PVDF) Films

2014 ◽  
Vol 1070-1072 ◽  
pp. 589-593
Author(s):  
Fei Peng Wang ◽  
Zheng Yong Huang ◽  
Jian Li
Keyword(s):  
Phase Transition ◽  
Crystalline Phase ◽  
High Speed ◽  
Vinylidene Fluoride ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Α Phase ◽  
Poly Vinylidene Fluoride ◽  
Crystalline Phase Transition

Commercial poly (vinylidene fluoride) (PVDF) films are uniaxially stretched with varying rates at 110 °C in order to endow PVDF piezo-and pyroelectric by crystalline-phase transition from α to β during the stretching. The crystalline phases are determined by infrared spectroscopy. The β-phase content and its fraction in films increase as a result of stretching with high rates. In addition, higher stretching rates yield a slight increase of γ phase. The crystallite size is evaluated by means of X-ray diffraction. It is found that the β-phase crystallites become smaller with fast stretching, whereas the α-phase crystallites are cracked and disappear at high-speed stretching of 2.5 /min.

Phase Transition in Poly(Vinylidene Fluoride) Investigated with Micro-Raman Spectroscopy

2005 ◽  
Vol 59 (3) ◽  
pp. 275-279 ◽  
Author(s):  
C. J. L. Constantino ◽  
A. E. Job ◽  
R. D. Simões ◽  
J. A. Giacometti ◽  
V. Zucolotto ◽  
...  
Keyword(s):  
Phase Transition ◽  
Raman Spectroscopy ◽  
Vinylidene Fluoride ◽  
Raman Band ◽  
X Ray Diffraction ◽  
X Ray ◽  
Micro Raman Spectroscopy ◽  
Β Phase ◽  
Α Phase ◽  
Poly Vinylidene Fluoride

The phase transition from the non-polar α-phase to the polar β-phase of poly(vinylidene fluoride) (PVDF) has been investigated using micro-Raman spectroscopy, which is advantageous because it is a nondestructive technique. Films of α-PVDF were subjected to stretching under controlled rates at 80 °C, while the transition to β-PVDF was monitored by the decrease in the Raman band at 794 cm−1 characteristic of the α-phase, along with the concomitant increase in the 839 cm−1 band characteristic of the β-phase. The α→β transition in our PVDF samples could be achieved even for the sample stretched to twice (2×-stretched) the initial length and it did not depend on the stretching rate in the range between 2.0 and 7.0 mm/min. These conclusions were corroborated by differential scanning calorimetry (DSC) and X-ray diffraction experiments for PVDF samples processed under the same conditions as in the Raman scattering measurements. Poling with negative corona discharge was found to affect the α-PVDF morphology, improving the Raman bands related to this crystalline phase. This effect is minimized for films stretched to higher ratios. Significantly, corona-induced effects could not be observed with the other experimental techniques, i.e., X-ray diffraction and infrared spectroscopy.

Electrically excited oscillation and crystalline structure of a nanoclay/poly(vinylidene fluoride) composite film

2011 ◽  
Vol 22 (18) ◽  
pp. 2103-2112 ◽  
Author(s):  
Go Murasawa ◽  
Akihiro Nishioka ◽  
Ken Miyata ◽  
Tomonori Koda ◽  
Hideo Cho
Keyword(s):  
Composite Film ◽  
Crystalline Structure ◽  
Vinylidene Fluoride ◽  
Composite Films ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Impedance Characteristics ◽  
Poly Vinylidene Fluoride ◽  
Excited Oscillation

This study was conducted to investigate electrically excited oscillation and crystalline structure of nanoclay/poly(vinylidene fluoride) (PVDF) composite films. First, nanoclay/PVDF composite films are fabricated by solvent casting. Second, their PVDF crystalline structure and nanoclay orientation are analyzed using x-ray diffraction. The impedance characteristics of films are then measured. Third, the oscillation excited from films as a result of applied voltage is measured. Thereby, we confirmed the presence of unoriented β-phase PVDF crystals and exfoliated-type nanoclay structure in a composite film. The output oscillation showed monotonic component corresponding to the input sinusoidal voltage at a high frequency range, although its amplitude is low.

scholarly journals Comparative Study of PVDF Sheets and Their Sensitivity to Mechanical Vibrations: The Role of Dimensions, Molecular Weight, Stretching and Poling

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1637
Author(s):  
Miroslav Mrlík ◽  
Josef Osička ◽  
Martin Cvek ◽  
Markéta Ilčíková ◽  
Peter Srnec ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Comparative Study ◽  
Vinylidene Fluoride ◽  
Initial Thickness ◽  
Complementary Method ◽  
Β Phase ◽  
Vibration Sensing ◽  
Poly Vinylidene Fluoride ◽  
Processing Techniques ◽  
The Comparative Study

This paper is focused on the comparative study of the vibration sensing capabilities of poly(vinylidene fluoride) (PVDF) sheets. The main parameters such as molecular weight, initial sample thickness, stretching and poling were systematically applied, and their impact on sensing behavior was examined. The mechanical properties of prepared sheets were investigated via tensile testing on the samples with various initial thicknesses. The transformation of the α-phase to the electro-active β-phase was analyzed using FTIR after applying stretching and poling procedures as crucial post-processing techniques. As a complementary method, the XRD was applied, and it confirmed the crystallinity data resulting from the FTIR analysis. The highest degree of phase transformation was found in the PVDF sheet with a moderate molecular weight (Mw of 275 kDa) after being subjected to the highest axial elongation (500%); in this case, the β-phase content reached approximately 90%. Finally, the vibration sensing capability was systematically determined, and all the mentioned processing/molecular parameters were taken into consideration. The whole range of the elongations (from 50 to 500%) applied on the PVDF sheets with an Mw of 180 and 275 kDa and an initial thickness of 0.5 mm appeared to be sufficient for vibration sensing purposes, showing a d33 piezoelectric charge coefficient from 7 pC N−1 to 9.9 pC N−1. In terms of the d33, the PVDF sheets were suitable regardless of their Mw only after applying the elongation of 500%. Among all the investigated samples, those with an initial thickness of 1.0 mm did not seem to be suitable for vibration sensing purposes.

Simulations of High-Strain Electrostrictive Chlorinated Terpolymers

2003 ◽  
Vol 785 ◽  
Author(s):  
George J. Kavarnos ◽  
Thomas Ramotowski
Keyword(s):  
Vinylidene Fluoride ◽  
High Strain ◽  
Polymer Chains ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lamellar Structures ◽  
Annealing Conditions ◽  
Poly Vinylidene Fluoride ◽  
Electromechanical Responses ◽  
Kinetics Of

ABSTRACTChlorinated poly(vinylidene fluoride/trifluoroethylene) terpolymers are remarkable examples of high strain electrostrictive materials. These polymers are synthesized by copolymerizing vinylidene fluoride and trifluoroethylene with small levels of a third chlorinated monomer. The electromechanical responses of these materials are believed to originate from the chlorine atom, which, by its presence in the polymer chains and by virtue of its large van der Waals radius, destroys the long-range crystalline polar macro-domains and transforms the polymer from a normal to a high-strain relaxor ferroelectric. To exploit the strain properties of the terpolymer, it is desirable to understand the structural implications resulting from the presence of the chlorinated monomer. To this end, computations have been performed on model superlattices of terpolymers using quantum-mechanical based force fields. The focus has been on determining the energetics and kinetics of crystallization of the various polymorphs that have been identified by x-ray diffraction and fourier transform infrared spectroscopy. The chlorinated monomer is shown to act as a defect that can be incorporated into the lamellar structures of annealed terpolymer without a high cost in energy. The degree of incorporation of the chlorinated monomer into the crystal lattice is controlled by annealing conditions and ultimately determines the ferroelectric behavior of the terpolymers.

scholarly journals Fabrication of Poly(Vinylidene Fluoride)/Graphene Nano-Composite Micro-Parts with Increased β-Phase and Enhanced Toughness via Micro-Injection Molding

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3292
Author(s):  
Wu Guo ◽  
Zhaogang Liu ◽  
Yan Zhu ◽  
Li Li
Keyword(s):  
Injection Molding ◽  
Vinylidene Fluoride ◽  
Structure Evolution ◽  
Phase Content ◽  
Micro Injection Molding ◽  
Nano Composite ◽  
Injection Speed ◽  
Β Phase ◽  
Poly Vinylidene Fluoride ◽  
Micro Parts

Based on poly(vinylidene fluoride)/graphene (PVDF/GP) nano-composite powder, with high β-phase content (>90%), prepared on our self-designed pan-mill mechanochemical reactor, the micro-injection molding of PVDF/GP composite was successfully realized and micro-parts with good replication and dimensional stability were achieved. The filling behaviors and the structure evolution of the composite during the extremely narrow channel of the micro-injection molding were systematically studied. In contrast to conventional injection molding, the extremely high injection speed and small cavity of micro-injection molding produced a high shear force and cooling rate, leading to the obvious “skin-core” structure of the micro-parts and the orientation of both PVDF and GP in the shear layer, thus, endowing the micro-parts with a higher melting point and crystallinity and also inducing the transformation of more α-phase PVDF to β-phase. At the injection speed of 500 mm/s, the β-phase PVDF in the micro-part was 78%, almost two times of that in the macro-part, which was beneficial to improve the dielectric properties. The micro-part had the higher tensile strength (57.6 MPa) and elongation at break (53.6%) than those of the macro-part, due to its increased crystallinity and β-phase content.

Structures and Physical Properties of Multi-Walled Carbon Nanotube-Filled PVDF Thermoplastic Composites

2007 ◽  
Vol 124-126 ◽  
pp. 1117-1120 ◽  
Author(s):  
Dong Wook Chae ◽  
Young Wan Nam ◽  
Seung Sangh Wang ◽  
S.M. Hong
Keyword(s):  
Carbon Nanotube ◽  
Vinylidene Fluoride ◽  
Thermoplastic Composites ◽  
Wide Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Loading Level ◽  
Multi Walled Carbon Nanotube ◽  
Poly Vinylidene Fluoride ◽  
Internal Mixer

Poly(vinylidene fluoride) (PVDF) / multi-walled carbon nanotube (MWNT) thermoplastic composites was melt compounded in an internal mixer. The percolation level for this system in electrical conductivity clearly occured between 2 and 2.5 wt%. PVDF/MWNT thermoplastic composites exhibited an increased crystallization temperature with the loading level, at 10 wt% loading by ca. 6. In addition, they presented a shoulder posterior to the main melting peak and an increased endpoint of the peak. In the Wide Angle X-ray Diffraction (WAXD) patterns, the incorporation of MWNT produced a larger shoulder at 2θ =20.7° with increasing the loading level, corresponding to the β-form crystal of PVDF.

The role of cerium(iii)/yttrium(iii) nitrate hexahydrate salts on electroactive β phase nucleation and dielectric properties of poly(vinylidene fluoride) thin films

RSC Advances ◽  
2015 ◽  
Vol 5 (36) ◽  
pp. 28487-28496 ◽  
Author(s):  
Pradip Thakur ◽  
Arpan Kool ◽  
Biswajoy Bagchi ◽  
Nur Amin Hoque ◽  
Sukhen Das ◽  
...  
Keyword(s):  
Thin Films ◽  
Dielectric Properties ◽  
Vinylidene Fluoride ◽  
Nitrate Hexahydrate ◽  
Yttrium Nitrate ◽  
Β Phase ◽  
Poly Vinylidene Fluoride ◽  
Phase Nucleation ◽  
Yttrium Nitrate Hexahydrate

Electroactive β phase nucleation in cerium/yttrium nitrate hexahydrate salt modified PVDF thin filmsviaformation of hydrogen bonds.

Effect of Thermal Treatment on the Physical Properties of Electrospun PVDF Membrane

2012 ◽  
Vol 591-593 ◽  
pp. 1113-1116
Author(s):  
Si Chen Cheng ◽  
Yin Zheng Liang ◽  
Yi Ping Qiu
Keyword(s):  
Thermal Treatment ◽  
Tensile Property ◽  
Tensile Testing ◽  
Vinylidene Fluoride ◽  
X Ray Diffraction ◽  
Electrospinning Technique ◽  
Pvdf Membrane ◽  
X Ray ◽  
Before And After ◽  
Poly Vinylidene Fluoride

The electrospinning technique was used to produce poly (vinylidene fluoride) (PVDF) membrane. Thermal treatment was introduced to improve the mechanical property and dimensional stability. In this paper, the PVDF membranes before and after thermal treatment were characterized by Scanning electron microscope (SEM), differential scanning calorimeter (DSC) and wide angle X-ray diffraction (WAXD), tensile testing. The crystallinity, tensile property, as well as melting temperature changed with the treated temperature. The results hows that thermal treatment could notably increase the tensile property of electrospun PVDF membrane and 160°C is a proper temperature for thermal treating

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