scholarly journals Characteristics of the Non-Isothermal and Isothermal Crystallization for the β Polymorph in PVDF by Fast Scanning Calorimetry

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2708
Author(s):  
Ernesto Pérez ◽  
Irene Angulo ◽  
Enrique Blázquez-Blázquez ◽  
María L. Cerrada
Keyword(s):  
Isothermal Crystallization ◽  
Vinylidene Fluoride ◽  
Polymer Science ◽  
Scanning Calorimetry ◽  
Isothermal Conditions ◽  
Β Phase ◽  
Fast Scanning Calorimetry ◽  
Poly Vinylidene Fluoride ◽  
The One ◽  
Very High

Structuring at very high rates has become one of the current and important topics of interest in polymer science, because this is a common protocol in the processing of films or fibers with industrial applicability. This work presents the study by fast scanning calorimetry, FSC, of poly(vinylidene fluoride), paying special attention to the conditions for obtaining the β phase of this polymer, because it is the one technologically more interesting. The results indicate that this β phase of poly(vinylidene fluoride) is obtained when the sample is isothermally crystallized at temperatures below 60 °C. Under non-isothermal conditions, the β polymorph begins to be observed at rates above 400 °C/s, although a coexistence with the α modification is observed, so that exclusively the β phase is obtained only at rates higher than 3000 °C/s.

scholarly journals Graphene Nanoplatelet-Reinforced Poly(vinylidene fluoride)/High Density Polyethylene Blend-Based Nanocomposites with Enhanced Thermal and Electrical Properties

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 361 ◽  
Author(s):  
Kartik Behera ◽  
Mithilesh Yadav ◽  
Fang-Chyou Chiu ◽  
Kyong Rhee
Keyword(s):  
Isothermal Crystallization ◽  
High Density Polyethylene ◽  
Vinylidene Fluoride ◽  
High Density ◽  
Scanning Calorimetry ◽  
Melt Mixing ◽  
Graphene Nanoplatelet ◽  
Polyethylene Blend ◽  
Poly Vinylidene Fluoride ◽  
Mixing Method

In this study, a graphene nanoplatelet (GNP) was used as a reinforcing filler to prepare poly(vinylidene fluoride) (PVDF)/high density polyethylene (HDPE) blend-based nanocomposites through a melt mixing method. Scanning electron microscopy confirmed that the GNP was mainly distributed within the PVDF matrix phase. X-ray diffraction analysis showed that PVDF and HDPE retained their crystal structure in the blend and composites. Thermogravimetric analysis showed that the addition of GNP enhanced the thermal stability of the blend, which was more evident in a nitrogen environment than in an air environment. Differential scanning calorimetry results showed that GNP facilitated the nucleation of PVDF and HDPE in the composites upon crystallization. The activation energy for non-isothermal crystallization of PVDF increased with increasing GNP loading in the composites. The Avrami n values ranged from 1.9–3.8 for isothermal crystallization of PVDF in different samples. The Young’s and flexural moduli of the blend improved by more than 20% at 2 phr GNP loading in the composites. The measured rheological properties confirmed the formation of a pseudo-network structure of GNP-PVDF in the composites. The electrical resistivity of the blend reduced by three orders at a 3-phr GNP loading. The PVDF/HDPE blend and composites showed interesting application prospects for electromechanical devices and capacitors.

Determination of the melting enthalpy of β phase of poly(vinylidene fluoride)

e-Polymers ◽  
2013 ◽  
Vol 13 (1) ◽  
Author(s):  
Arkadiusz Gradys ◽  
Pawel Sajkiewicz
Keyword(s):  
Thermodynamic Stability ◽  
Vinylidene Fluoride ◽  
Melting Enthalpy ◽  
Dimethyl Formamide ◽  
Scanning Calorimetry ◽  
Temperature Range ◽  
Β Phase ◽  
Α Phase ◽  
Poly Vinylidene Fluoride ◽  
Limited Temperature Range

Abstract Wide Angle X-ray Scattering (WAXS), Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared spectroscopy (FTIR) analyses of phase composition and of thermal properties of PVDF samples, crystallized at temperatures 27 - 155 °C by casting from N,N-dimethyl formamide (DMF) solution, are reported. Samples obtained at 27 °C contain only β crystal phase and with increase of casting temperature content of β phase decreases in favor of α phase. Evaluation of combined: phase content (WAXS) and melting heat (DSC), leads to two fold higher than for 100 % α phase value of 100% β melting enthalpy, ΔHβ0= 219.7 J.g-1, which may be justified by strong polar interactions in β phase TTT conformation. The relation ΔHβ0 > ΔHα0 leads either to the thermodynamic stability of β phase in whole temperature range (if Tmβ0 ≥ Tmα0) or to the limited temperature range of thermodynamic stability of α phase (if Tmβ0 < Tmα0).

Enhancement effects of two kinds of carbon black on piezoelectricity of PVDF-HFP composite films

2015 ◽  
Vol 08 (03) ◽  
pp. 1540006 ◽  
Author(s):  
Bin Hu ◽  
Ning Hu ◽  
Liangke Wu ◽  
Hao Cui ◽  
Ji Ying
Keyword(s):  
Carbon Black ◽  
Open Circuit Voltage ◽  
Vinylidene Fluoride ◽  
Composite Films ◽  
Open Circuit ◽  
Scanning Calorimetry ◽  
Crystallinity Degree ◽  
Β Phase ◽  
Poly Vinylidene Fluoride ◽  
Scanning Electron

Two kinds of carbon black (CB) (i.e., CB#300 and CB#3350) were added into poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), respectively, to improve its piezoelectricity. The results revealed that when 0.5 wt.% CB was added, the best performance of the PVDF-HFP/CB composite films was obtained. The calibrated open circuit voltage and the density of harvested power of 0.5 wt.% CB#3350 contained composite films were 204%, and 464% (AC) and 561% (DC) of those of neat PVDF-HFP films. Similarly, for 0.5 wt.% CB#300 contained films, they were 211%, and 475% (AC) and 624% (DC), respectively. The enhancement mechanisms of piezoelectricity were clarified by the observation of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscope (SEM). We found that the added CBs act as nucleate agents to promote the formation of elongated, oriented and fibrillar β-phase crystals during the fabrication process, which increase the piezoelectricity. Overdosed CBs lead to a lower crystallinity degree, resulting in the lower piezoelectricity. Compared with CB#3350, CB#300 performs slightly better, which may be ascribed to its higher specific surface area.

Poly(vinylidene Fluoride)/Microcrystalline Cellulose Nanocomposites with Enhanced Compatibility and Properties

2011 ◽  
Vol 471-472 ◽  
pp. 355-360 ◽  
Author(s):  
Xue Gang Tang ◽  
Meng Hou ◽  
Jin Zou ◽  
Rowan Truss
Keyword(s):  
Microcrystalline Cellulose ◽  
Vinylidene Fluoride ◽  
Attenuated Total Reflectance ◽  
Scanning Calorimetry ◽  
Elongation At Break ◽  
Total Reflectance ◽  
Β Phase ◽  
Transmission Electron ◽  
Poly Vinylidene Fluoride ◽  
Cellulose Nanocomposites

Poly(vinylidene fluoride)/Microcrystalline cellulose (MCC) nanocomposites were prepared by ultrasonic treatment and magnetic stir. Poly(vinylidene fluoride)-graft-maleic anhydride (PVDF-g-MAH) was added to promote matrix–filler compatibility. Transmission electron microscopy (TEM) results showed that the diameter of the MCC was decreased to several tens nanometers by the treatment of ultrasonic and magnetic stir. The results of differential scanning calorimetry (DSC) showed that the peak crystallisation temperatures (Tc) and the crystallisation enthalpy ΔHc increased with the addition of MCC, and the melting enthalpy ΔHm increased. With the addition of the compatibilizer (PVDF-g-MAH), peak crystallisation temperatures increased further, while without further increase of the ΔHc. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) showed that the addition of MCC induced β-phase PVDF, and the addition of PVDF-g-MAH can induce more β-phase PVDF. Mechanical properties of the nanocomposites were evaluated and the results showed that the addition of MCC did not increase the Young’s modulus, while the tensile strength and elongation at break decreased.

scholarly journals Influences of poling temperature and elongation ratio on PVDF-HFP piezoelectric films

2021 ◽  
Vol 10 (1) ◽  
pp. 1009-1017
Author(s):  
Zhaonan Jin ◽  
Dan Lei ◽  
Yang Wang ◽  
Liangke Wu ◽  
Ning Hu
Keyword(s):  
High Efficiency ◽  
Vinylidene Fluoride ◽  
Low Cost ◽  
Maximum Output ◽  
Elongation Ratio ◽  
Scanning Calorimetry ◽  
Poling Process ◽  
Β Phase ◽  
Poly Vinylidene Fluoride ◽  
Mechanical Stretching

Abstract Poly(vinylidene fluoride) (PVDF) and its copolymers exhibit excellent piezoelectric properties and are potential materials for high efficiency energy harvesting devices. In this study, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) films are prepared by the solution casting method. The prepared film is then subjected to mechanical stretching and poling process. By adjusting the temperature of the poling process and the elongation ratio of the mechanical stretching process, the relative content of β-phase F(β) increases significantly, leading to high piezoelectric performance. The maximum output voltage of the PVDF-HFP films poled at 40°C reaches 3.67 V, 71% higher than that of the films poled at room temperature. Fourier transform infrared spectroscopy analysis (FTIR), XRD (X-ray diffraction), and differential scanning calorimetry are used to investigate the influences of mechanical stretching and poling process on the crystal structure to discover the enhancement mechanism. This work provides a straightforward and low-cost route to prepare high piezoelectric PVDF-HFP-based materials.

High Efficient and Continuous Triboelectric Power Harvesting based on Porous β-phase Poly (vinylidene fluoride) Aerogel

2021 ◽  
Author(s):  
Minmin Wang ◽  
Weiqun Liu ◽  
Xu Shi ◽  
Jinyang Pan ◽  
Bing Zhou ◽  
...  
Keyword(s):  
Vinylidene Fluoride ◽  
High Electron ◽  
Exchange Method ◽  
Power Harvesting ◽  
Β Phase ◽  
Output Performance ◽  
High Electron Affinity ◽  
High Efficient ◽  
Poly Vinylidene Fluoride ◽  
High Output

Non-additive β-phase porous poly (vinylidene fluoride) (PVDF) aerogel with high electron affinity is successfully prepared through simple solvent exchange method. The as-prepared additive-free PVDF aerogel shows high output performance used...

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.

scholarly journals Studies on the electrostatic effects of stretched PVDF films and nanofibers

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Yixuan Lin ◽  
Yuqiong Zhang ◽  
Fan Zhang ◽  
Meining Zhang ◽  
Dalong Li ◽  
...  
Keyword(s):  
Vinylidene Fluoride ◽  
Polarized Light ◽  
Transition Process ◽  
Open Circuit ◽  
Wearable Electronics ◽  
Energy Harvesters ◽  
Β Phase ◽  
Poly Vinylidene Fluoride ◽  
Piezoelectric Effects ◽  
Energy Harvesting Devices

AbstractThe electroactive β-phase in Poly (vinylidene fluoride, PVDF) is the most desirable conformation due to its highest pyro- and piezoelectric properties, which make it feasible to be used as flexible sensors, wearable electronics, and energy harvesters etc. In this study, we successfully developed a method to obtain high-content β-phase PVDF films and nanofiber meshes by mechanical stretching and electric spinning. The phase transition process and pyro- and piezoelectric effects of stretched films and nanofiber meshes were characterized by monitoring the polarized light microscopy (PLM) images, outputting currents and open-circuit voltages respectively, which were proved to be closely related to stretching ratio (λ) and concentrations. This study could expand a new route for the easy fabrication and wide application of PVDF films or fibers in wearable electronics, sensors, and energy harvesting devices.

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