Effect of Mechanical Treatment Temperature on Electrical Properties and Crystallite Size of PVDF Film (original) (raw)
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Effect of thermal processing conditions on the structure and dielectric properties of PVDF films
The effect of annealing and quenching temperatures on the crystallinity, β phase fraction and dielectric behavior of poly (vinylidene fluoride) (PVDF) have been studied. The crystallinity and β phase fraction of these films were evaluated using X-ray diffraction and FTIR techniques for different annealing and quenching temperatures. It is seen that the thermal processing conditions play a crucial role in determining the dominant phase in PVDF. The β phase PVDF is the most desired phase for device applications such as sensors and actuators. Hence, the thermal processing conditions are optimized for obtaining β rich PVDF films. The β rich phase of PVDF is obtained for films which are annealed at 80 °C and quenched at 20 °C. The as-synthesized films for the optimized processing conditions was studied for their dielectric behavior and was found to exhibit dielectric constant as high as ~60.
Characterization Analysis of PVDF Thin Films Fabricated Using Deep Coating Machines
Proceedings of the International Conference on Science and Technology (ICOSAT 2017), 2018
Development of Polyvinylidene Fluoride (PVDF) thin film manufacturing technologies is rapidly increasing. Various fabrication methods continue to evolve. In this paper described about the fabrication of PVDF thin films using deep coating. Fabrication of PVDF films made for several samples with variations of temperature and duration of heating. Piezoelectric properties of PVDF as well as the fraction of the value of β is the focus of which is discussed in the paper. The amount of beta fraction samples will determine the quality of thin films made. To see how much the value of the beta fraction sampled sample characterization using FTIR and XRD. Characterization of the results obtained is then performed calculations to determine how much beta fraction of the sample. From the calculations, the fraction of beta to increase the heating temperature of 70 0 C to 110 0 C in a row is: 37%, 38%, 44%, 50% and 58%. Further more for variations in the length of time to warm up 10 minutes, 20 minutes and 30 minutes fractions beta values obtained by 34%, 48% and 60%. These results indicate that the PVDF thin films fabricated using deep coating method has produced samples of PVDF films with good piezoelectric properties. Of research is well known that the optimum annealing temperature was 110 0 C and the optimum length of heating time is 30 minutes.
α- and γ-PVDF: Crystallization kinetics, microstructural variations and thermal behaviour
Materials Chemistry and Physics, 2010
The kinetics of the isothermal crystallization from the melt of ␣and ␥-poly(vinylidene fluoride), PVDF, and the corresponding melting behaviour has been investigated. The crystallization kinetics was evaluated on the basis of the theory of Avrami. The variation of the microstructure of the samples crystallized at different temperatures was monitored along time by optical microscopy with polarized light. The correlation between microstructure and kinetic parameters allows tailoring the microstructure of the polymer by choosing specific crystallization conditions. Infrared spectroscopy and Raman spectroscopy show the appearance of the ␥-phase for higher crystallization temperatures.
Polymer, 2001
The present work focuses on the effects of thermomechanical history on the structure and mechanical behaviour of PVDF. In the ®rst part of our investigation differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) are used to follow the evolution of the structure of PVDF after different annealing treatments or deformation. Processing has a signi®cant impact on the quantities of the amorphous and crystalline phases and their interphase. Subsequent annealing affects these phases in a different proportion. This in¯uence depends on the position of the annealing temperature in comparison with the upper glass transition temperature of PVDF. Deformation induces conformational change in the injection moulded samples. Thus, the a conformation is transformed to the b conformation. The b conformation also has a noticeable in¯uence on the mechanical behaviour of the material, which will be discussed in the second part of our study.
Characterization of poled and non-poled β-PVDF films using thermal analysis techniques
Thermochimica Acta, 2004
-poly(vinylidene fluoride)--PVDF-exhibits ferroelectric properties due to the special arrangement of the chain units in the crystalline phase. The ferroelectric phase can be optimised by poling the original stretched film, that tends to align the randomly organised crystallites against the applied field. In this work, polarised and non-polarised -PVDF from the same batch are characterised by mechanical tests and a series of thermal analysis techniques, including DMA, TMA and DSC. The films exhibit mechanical anisotropy, and in the longitudinal direction the poled film presents larger mechanical properties, due to the higher structural organisation. Poled and non-poled show similar crystallinity levels but the melting temperature probed by DSC is higher for the non-poled film; for both films the melting peak exhibits a complex shape, indicating a heterogeneous crystalline organization. Two relaxation processes were found ( and ␣ c ) by dynamic mechanical analysis (DMA). The  process, attributed to segmental motions in the amorphous phase, appears at the same temperature in both directions, but its intensity was found to be higher for the films tested in the longitudinal direction. For a given direction, the poled films exhibit lower peaks, due to the more organised amorphous structure. At higher temperature, the ␣ c -relaxation was related to the contraction of the films in the longitudinal direction during heating, recorded by thermal mechanical analysis (TMA). The onset of molecular mobility within the crystalline phase allows for cooperative diffusion processes in the amorphous phase, generating the randomisation of the initially oriented structure.
IOSR Journal of Applied Physics, 2013
In this report pure poly(vinylidene fluoride) (PVDF) films were prepared by casting method using acetone solvent. The crystallization of both α and β phase from acetone solvent by varying the time of crystallization has been described. This paper also describes the enhancement of β phase at different annealing condition. β phase dominant thin films were obtained when as cast thin films were annealed at 90 ºC for 5 hours. The PVDF films with dominant α-phase were obtained, when time of crystallization is extend. From (Xray diffraction) XRD and Fourier Transform Infrared Spectrum (FTIR) it is confirmed that the PVDF thin films, cast from acetone solution and annealed at 90 ºC for 5 hours, have maximum percentage of β-phase. Presence of the crystalline α and β phases in each sample was confirmed by X-ray Diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). We found that of PVDF when crystallized from its acetone solutions led to the formation of β phase. UV-visible optical absorption analysis revealed a change in the optical gap and shift in absorption edge with annealing temperature.
Influence of the Crystallisation Kinetics on the Microstructural Properties of α-PVDF
MRS Proceedings, 2006
ABSTRACTThe kinetics of the isothermal crystallization from the melt at different crystallisation temperatures and the melting behaviour of Poly(vinylidene fluoride) (PVDF) in the alpha phase has been investigated. The variation of the microstructure of the samples crystallized at different temperatures was monitored with time by Optical Microscopy. The correlation between microstructure and kinetic parameters allows the tailoring of the microstructure by choosing the crystallisation conditions of the samples. Raman and Infrared Transmission Spectroscopy also show the appearance of the γ-phase for higher crystallisation temperatures. The influence of the crystallisation kinetics on the degree of crystallinity of the samples will be also presented and discussed.
Properties of PVDF films stretched in machine direction
Polymers and Polymer Composites, 2020
Polyvinylidene fluoride (PVDF) films possess superior piezoelectric properties due to the β-phase obtained by methods, such as addition of nanofillers, application of high electric field, use of polar solvents and mechanical stretching. Simultaneous stretching and heating of the films can reduce porosity, increase transformation from α-phase to β-phase, and hence, improve their piezoelectric properties. This article presents the effects of stretching PVDF films on the β-phase formation and the resulting mechanical properties. A custom-designed stretching unit with roller mechanism and heating provision was employed for the purpose. The 200% stretched films at 100°C showed 86.79% β-phase, which is in correlation with X-ray diffraction peaks at 2 θ = 20.3–20.6°. Transmission electron microscopy and scanning electron microscopy of the stretched films revealed spherulitic to lamellar transformation and decrease in porosity. Stretching increased crystallinity from 32.99% to 44.84%. Nanoi...
Effects of static electricity and fabrication parameters on PVDF film properties
Bulletin of Materials Science
Degree of crystallinity and β-phase fraction are important factors in determining electroactive polymers performance. In the present work, effects of intrinsic static electricity, substrate type, PVDF solution concentration and drying temperature on β-phase fraction and degree of crystallinity in fabricated PVDF films were studied using XRD, Raman spectroscopy and FTIR techniques. In particular, this paper investigates the influence of static electricity on PVDF film properties for the first time. The results show that discharging static electricity from the PVDF solution is highly effective in reducing the amount of residual solvent. It was found that a lower amount of residual solvent and higher drying temperature resulted in a higher degree of crystallinity. Further, a high fraction of β phase was observed in all PVDF films due to more polar solvent effect that it was hardly affected by other parameters such as static electricity.
Effect of annealing temperature on dielectric behavior of PVDF thick films
Nucleation and Atmospheric Aerosols, 2017
Highly (111)-oriented lanthanum modified lead zirconate titanate (Pb 0.98 La 0.02)(Zr 0.95 Ti 0.05) 0.995 O 3 thin films with the thickness of 300 nm were fabricated by a sol-gel method. Electrical measurements were conducted on (Pb 0.98 La 0.02)(Zr 0.95 Ti 0.05) 0.995 O 3 thin films. Well-saturated hysteresis loops were achieved with an applied voltage of 19 V. Dielectric constant and dielectric loss as a function of frequency for (Pb 0.98 La 0.02)(Zr 0.95 Ti 0.05) 0.995 O 3 thin films annealed at 670°C were measured. Dc bias field dependence of dielectric constant and dielectric loss were conducted at room temperature; the dielectric tunability of (Pb 0.98 La 0.02)(Zr 0.95 Ti 0.05) 0.995 O 3 thin film annealed at 670°C was 20.3 %. The pyroelectric coefficient of films was measured by a dynamic technique. The pyroelectric coefficients of (Pb 0.98 La 0.02)(Zr 0.95 Ti 0.05) 0.995 O 3 thin films annealed at 570, 620 and 670°C were 208, 244 and 192 lC/m 2 K, respectively. It was found that the pyroelectric property was highly depended on the annealing temperature.