Properties Of Polyvinylidene Fluoride Research Articles

The effect of core-shell BaTiO3@SiO2 on the mechanical and dielectric properties of PVDF composites

ABSTRACT In this study, polymer composite films were prepared by the solution casting method using ceramic filler barium titanate (BT) to enhance the mechanical and dielectric properties of polyvinylidene fluoride (PVDF). A silicon dioxide (SiO2) shell was coated on BT surface by hydrolysis reaction of tetraethyl orthosilicate (TEOS) at different concentrations in order to provide a strong interface between PVDF and BT. The influence of SiO2 coating on morphology, structure, thermal, tensile and dielectric properties of composites were investigated compared to neat PVDF. The results of analyses show that SiO2 is successfully coated on BT and that the ceramic filler enhances the tensile and dielectric properties of the composites. At low BT concentrations (5 and 10 vol.%) the tensile strength and Young modulus are improved compared to neat PVDF. For films having a high content of SiO2, in particular, coated BT high values, such as 24.8 at 102 Hz are found for the dielectric constant, which is greatly improved by almost 2.3 times compared to neat PVDF. Properties, such as flexibility and thermal stability, are well retained in the prepared composites.

In Vitro Cell Interactions on PVDF Films: Effects of Surface Morphology and Polar Phase Transition.

In recent years, several studies have validated the use of piezoelectric materials for in situ biological stimulation, opening new interesting insights for bio-electric therapies. In this work, we investigate the morphological properties of polyvinylidene fluoride (PVDF) in the form of microstructured films after temperature-driven phase transition. The work aims to investigate the correlations between morphology at micrometric (i.e., spherulite size) and sub-micrometric (i.e., phase crystallinity) scale and in vitro cell response to validate their use as bio-functional interfaces for cellular studies. Morphological analyses (SEM, AFM) enabled evidence of the peculiar spherulite-like structure and the dependence of surface properties (i.e., intra-/interdomain roughness) upon process conditions (i.e., temperature). Meanwhile, chemical (i.e., FTIR) and thermal (i.e., DSC) analyses highlighted an influence of casting temperature and polymer solution on apolar to polar phases transition, thus affecting in vitro cell response. Accordingly, in vitro tests confirmed the relationship between micro/sub-microstructural properties and hMSC response in terms of adhesion and viability, thus suggesting a promising use of PVDF films to model, in perspective, in vitro functionalities of cells under electrical stimuli upon mechanical solicitation.

Investigating the effect of PEG200 and two-dimensional h-BN on PVDF membrane performance for membrane distillation–crystallization

Although water supplies are prominently dependent on desalination technology, desalination plant facing severe issues of discharged brine concentrate. Membrane distillation crystallization is an emerging synergistic technology that resolves the issue of brine concentrate by recovering clean water and value-added minerals simultaneously. In the present study, properties of polyvinylidene fluoride (PVDF) membrane were modified by incorporation of exfoliated fillers of hexagonal boron nitride and polyethylene glycol. The changes in morphology, surface roughness, hydrophobicity, thermal stability, and chemical composition of the prepared membranes were evaluated by scanning electron microscopy, atomic force microscopy, contact angle, thermogravimetric analysis, Fourier-transform infrared spectroscopy, respectively. Membrane distillation crystallization experiments were conducted to observe the effect of modified membranes on the permeate flux and salts recovery at different feed temperatures. The results showed a significant improvement in the permeate flux with modified membranes compared with pure PVDF membrane. It was found that hexagonal boron nitride/polyethylene glycol200 incorporated PVDF membrane gave the higher permeate flux (3.41 kg/m2 h for K2SO4 and 2.62 kg/m2 h for KNO3) at a temperature of 80 °C along with higher salts recovery than pure PVDF membranes. A 100 h long run test was conducted on modified membranes, which showed consistency in permeate flux with a marginal increase in conductivity.

Formation of the structure and properties of polyvinylidene fluoride and composites based on it, prepared by explosive pressing

The possibility of forming PVDF composites with 20% Al2O3 content by explosive pressing in a cylindrical ampoule is shown. It has been established that a change in pressure when using this pressing method leads to the implementation of various compaction mechanisms for PVDF and its composites. A change in pressure affects almost all characteristics of the polymer and the composites being formed, up to their partial destruction.

Synergistic effects of stretching/polarization temperature and electric field on phase transformation and piezoelectric properties of polyvinylidene fluoride nanofilms

This study aims to investigate the dependence of crystalline structure and piezoelectric properties of polyvinylidene fluoride stretched films (up to four times their initial length) as a function of temperature, polarization under constant field as well as varying electric field at constant polarization temperature. X-ray diffraction analysis indicates that α → β phase transformation occurs below 80 °C; meanwhile, the crystallinity is improved with stretching temperature reaching 44% compared to 32% for un-stretched. FTIR analysis confirms the results obtained by XRD, as new functional groups, shift of peaks position as well as reduction in their relative intensity are observed. It is found that the piezoelectric coefficient (d33) decreases with increasing temperature, while it increases with the electric field. The obtained results are discussed on the basis of the dependence of (d33) as a function of phase (α + β + amorphous) composition and the degree of crystallinity associated with various vibrational modes and the arrangement of hydrogen and fluorine atoms (corresponding charge H+ and F−) from either sides of PVDF skeleton chains arising upon the influence of thermomechanical treatment, polarization and electric field.

Influence of adding carbon black on electrical conductivity in dynamically vulcanized of poly (vinylidene fluoride)/fluoroelastomer composites

The present work was focused on studying the effects of different CB loadings on the rheological, thermal, tensile, dynamic mechanical, and electrical properties of polyvinylidene fluoride and FKM composites. To these ends, dynamic mechanical thermal analysis (DMTA) was conducted, and the CB grade and method chosen for compound preparation were CB (N330) by melt mixing with different shear effects were examined, respectively. The composites were melt-blended with CB at 190 °C in an internal mixer, after which the properties of filled and unfilled composites were compared. The DMTA analysis revealed that the area under the loss tangent (tanδ) peak decreased and that the tanδ temperature of the rubber phase increased with CB loading. The presence of CB improved the mechanical properties, such as the Young’s modulus and tensile strength, of the composites and increased thermal stability given the high thermal stability of CB and the interaction between the CB particles and the polymer matrices. The increase in the electrical conductivities of the composites under different CB loadings was also examined with different shear effects because of the different dispersion states of CB. The percolation threshold of conductive thermoplastic vulcanizate composite based on conductive CB was observed and the experimental data could be well fitted to the general equation model.

Thermal, Tensile, Electrical, Dynamic Mechanical Thermal and Rheological Properties of Polyvinylidene Fluoride and Fluoroelastomer Composites Filled with Carbon Black

AbstractThe present work was focused on studying the effects of different CB loadings on the rheological, thermal, tensile, dynamic mechanical and electrical properties of polyvinylidenefluoride (PVDF) and FKM composites. To these ends, the CB grade and method chosen for compound preparation were CB (N330) and melt mixing, respectively. The composites were melt blended with CB at 190 °C in an internal mixer, after which the properties of filled and unfilled composites were compared. The presence of CB improved the mechanical properties, such as the Young's modulus and tensile strength, and increased thermal stability given the high thermal stability of CB and the interaction between the CB particles and the polymer matrices. The dynamic mechanical thermal analysis (DMTA) showed the glass transition temperatures of the composites. The analysis also revealed that the area under the loss tangent (tan δ) peak decreased and that the tan δ temperature of the rubber phase increased with CB loading. The increase in the electrical conductivity of the composites under different CB loadings was also examined, and the percolation threshold of conductive thermoplastic vulcanizate composite based on conductive CB was observed. The effect of CB and its content on rheological behavior of the PVDF/FKM blends was studied and the experimental data was correlated by a physical model named General Equation Model (GEM). A relation between rheology and conductivity of the blends with filler percolation was found.

Effect of formation of micro reaction locations (MRLs) on properties of polyvinylidene fluoride (PVDF) membranes

Micro reaction locations (MRLs) formed in membrane impact the integrated properties of membrane. In this paper, in order to form effective MRLs in PVDF membrane which performs attractive properties, YxFeyZr1-x-yO2 solid superacid coated TiO2 nanotubes (MSYFZr-TiNs) modified by sodium dodecylbenzene sulfonate (SDBS) are embedded into PVDF to prepare MSYFZr-TiNs/PVDF composite membranes with effective MRLs inside channels and on the surface of membranes. MSYFZr-TiNs and MSYFZr-TiNs/PVDF composite membranes are characterized and tested. The results show that YxFeyZr1-x-yO2 solid superacid with stable tetragonal phase reaches a hammett acidity of − 16.468, decomposing inorganic pollutants or restraining their formation inside channels and surface. The MSYFZr-TiNs/PVDF composite membranes with MRLs perform attractive anti-compaction and anti-fouling properties through MRLs. The water contact angle, stable degradation ratios for oil and Fe2O3 are 36.5°, 13.2% and 12.1%, respectively. Furthermore, when treating oily wastewater, the membrane permeate flux and oil retention ratio are 354 L m−2 h−1 and 93.48%, respectively. Therefore, MSYFZr-TiNs/PVDF composite membranes will possess desirable application in water cleaning.

Rheological, crystallization and electrical properties of poly vinylidene fluoride filled with micron iron

Micron iron was added into poly(vinylidene fluoride) (PVDF) via solution method to prepare the PVDF conductive composites. The electrical properties, non‐isothermal crystallization kinetics, crystal form, rheological, and thermal properties of PVDF/Fe composites were studied. Compared with neat PVDF, the PVDF/Fe composites had a higher crystallization rate, thermal stability and conductivity, but both crystallinity and flow property would decrease. The PVDF/Fe composites were subsequently treated by an alternating magnetic field. The percolation threshold value of the composites was found to reduce from 30 vol % to 11 vol %. The conductivity of the PVDF/Fe composites after alternating magnetic treatment increased by 8 orders of magnitude in comparison to neat PVDF, and the electrical conductivity of the PVDF/Fe composite with 30 vol % iron content was about 10−0.58 S m−1. The iron particles were more likely to form a conductive network in the polymer matrix after the magnetic field treatment according to morphological observation. The present work will supply an insight into the design of PVDF conductive composites as well as the further studies on the relationship between structure and property of polymer composites. POLYM. COMPOS., 40:E88–E101, 2019. © 2017 Society of Plastics Engineers

Study of the effects of holmium and 2-aminoterephthalate additions on the optical properties of polyvinylidene fluoride

ABSTRACTIn the present work the optical properties of Polyvinylidene Fluoride (PVDF) have been studied as a function of the content of holmium oxide (Ho), 2-amino terephthalate (AMT) and Ho-AMT compounds as modifiers. The characterization of the samples performed by the Fourier Transform Infrared Spectroscopy (FT-IR), Optical Absorption (UV-Vis) and Optical Fluorescence Spectroscopy. The FT-IR studies have shown that the relative percentage of β phase does not change as a function of the concentration. The fluorescence measurements have shown that the AMT and Ho-AMT compound addition increase the bandwidth at half maxima of PVDF samples. Finally, these results reveal that the PVDF samples studied in this work have potential for some interesting optical applications.

Fouling behaviour of membranes with different characteristics by urban wastewater secondary effluent

ABSTRACTFouling behaviours and antifouling properties of polyvinylidene fluoride (PVDF) ultrafiltration membranes blending with polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP) and polymethyl methacrylate (PMMA) had been investigated using the secondary effluent as the filtration medium. The results demonstrated that the antifouling properties of membranes using PVA and PVP as the additives were generally stronger than those using PMMA. Additives PVA and PVP could effectively improve the structural property and hydrophilicity of the membrane and result in an outstanding antifouling property. A dense membrane surface could prevent low molecular foulants from entering into the membrane pores, depositing on the membrane with a loose spongy layer and penetrating into the internal macropore structure. The not fully generated internal macropores on the membrane surface were trend to be plugged, which resulted in serious flux decay and the membrane fouling was irreversible. Filtration cake formed on the membrane due to concentration polarization, which caused membrane flux decline and high flux recovery after cleaning.

Research on the Technology of Flexible Tactile Type Sensor

The application filed and characteristics of flexible tactile sensor are introduced in this paper. Main technologies including microelectronics mechanical system and other new material of flexible tactile sensor are proposed. The structure and the working principle of microelectronics mechanical system used in flexible sensor are described and explained. The principle of piezoresistive of strain gauge is researched on. The piezoelectric properties of polyvinylidene fluoride is also narrated. The coupling effect of the dielectric mechanical properties and the dielectric mechanical properties are discussed. The conductive mechanism and the piezoresistive effect of flexible tactile sensor based on conductive rubber are analyzed. Physical properties of main technology of flexible tactile sensor are proposed summarily. Moreover, advantages and disadvantages of technologies above are analyzed. Some problems to be solved and research contents of flexible tactile sensor are put forward.

Influence of the processing method on the properties of a PVDF film

The main electrophysical properties of polyvinylidene fluoride (PVDF) films produced by two technologies: the solution casting method and the method of hot pressing from the melt are investigated. To analyze the PVDF films, methods of dielectric spectroscopy (DS), IR spectroscopy, TGA/DSC analysis, and x-ray diffraction (XRD) are used. It is demonstrated that the IR spectra of both PVDF films change weakly in comparison with the virgin PVDF film. The absorption bands characteristic for α-, β-, and γ-phases are observed for the virgin and both types of PVDF films. This testifies to the fact that the molecular structure of film samples is practically independent of their processing method. The only difference is that the new absorption band at 1723 cm–1 arises in the IR spectra of the films produced by the method of hot pressing from the melt. The TGA/DSC analysis demonstrates that the beginning melting temperature, melting temperature, beginning decomposition temperature, and decomposition temperature for the film samples produced by the method of hot pressing from the melt decrease by 8, 2, 10, and 12°C, respectively, compared to the film samples produced by the solution casting method.

Research on the Superhydrophobic Modification of Polyvinylidene Fluoride Membrane

In order to improve the hydrophobic property of Polyvinylidene fluoride (PVDF) membrane, in this paper nano-silica was modified by silane coupling agent firstly, then the modified nano-silica mixed with fluororesin，crosslinking agent and thickener to prepare the super-hydrophobic surface coating, finally the surface coating was covered on PVDF membrane. The results showed that the contact angle of the modified membrane was 162°and the sliding angle was 4°. The modified membrane was test by SEM and AFM, the surface coating on the PVDF membrane formed micro/nano-meter structure such as lotus leaves surface.

A Study of the Properties of Polyvinylidene Fluoride Modified with Nickel Nanoparticles

A Study of the Properties of Polyvinylidene Fluoride Modified with Nickel Nanoparticles

Effect of parameters of the butt pressure welding process on the strength and ductile properties of polyvinylidene fluoride – PVDF – tubular joints

The method most often used for permanent joining of thermoplastic elements is that of butt pressure welding. So far, the investigations carried out at Instytut Spawalnictwa (The Welding Institute) have been focussed on the assessment of the quality of joints made in basic grades of thermoplastics, such as polyethylene (PE), and polypropylene (PP) by the fusion and pressure welding processes, and also, on the technology of these methods. These particular materials are widely used in a variety of plastic constructions such as gas, water and drain pipelines, chemical installations, installations for desulphurisation of combustion gases in power plants, and so on. As the use of plastics for more specific constructions increases, new materials of enhanced properties appear. They are characterised by their higher degrees of purity, a wider range of working temperatures, higher strength, resistance to ultraviolet radiation, etc. Polyvinylidene fluoride (PVDF) belongs to this group.

Dynamic mechanical testing of the creep and relaxation properties of polyvinylidene fluoride

The paper concerns material testing and characterizations of the time-dependent properties of polyvinylidene fluoride (PVDF), a thin film piezoelectric polymer. The study is based on the assumptions of linear viscoelastic theory of hereditary type and time-temperature equivalence principle. A developed experimental program involves quasi-static creep tests and dynamic mechanical tests. The results of this study validate the assumptions of linear viscoelasticity in application to PVDF thin films and provide consistent empirical database regarding the creep and relaxation properties of PVDF in the material directions parallel and perpendicular to the orientation of the aligned molecular chains of the polymer.

Effects of Sample Processing and High-Energy Electron Irradiation Conditions on the Structural and Transitional Properties of P(VDF-TrFE) Copolymer Films

AbstractRecently it has been demonstrated that using a high electron energy irradiation, the electromechanical properties of polyvinylidene fluoride - trifluoroethylene, P(VDF-TrFE) copolymers can be improved significantly for example; high electric field induced strain (∼ 4.5%) with high elastic energy density, high dielectric constant (∼ 65 with loss less than at 1kHz), high piezoelectric coefficient (∼ 350 pm/V ) and high electro-mechanical coupling coefficient (∼0.45). It was found, depending on sample processing and electron irradiation conditions these properties can be controlled. In this talk we will present the experimental data on the effect of processing and irradiation conditions on structural and transitional behavior of copolymers. These structural information coupled with the electro-mechanical properties will be presented in order to show the possibilities for further improvement.

Static and dynamic pyroelectric properties of PVDF

Abstract The pyroelectric properties of polyvinylidene fluoride (PVDF) have been investigated with a new procedure for the simultaneous measurement of the pyroelectric coefficient under quasistatic and dynamic conditions. The sample is heated at a uniform rate with an overlaid sinusoidal temperature modulation. The dc and the ac component of the electric current are recorded, and the dc and ac components of the temperature are measured with a thin film resistive bolometer. The quasistatic measured pyroelectric coefficient is higher than the dynamic one, with a quotient of both quantities up to three. The frequency dependence of the pyroelectric coefficient has been investigated down to 10−3 Hz, showing a contribution of free charges to the pyroelectric current for frequencies below the reciprocal dielectric relaxation time. The results show, that the polarization of the crystalline regions is locally compensated by charge, and that even a small change of the polarization is compensated within a time scale...

Investigation of poling field effects on PVDF pyroelectric detectors: Photoacoustic thermal diffusivity measurements

The influence of poling fields on the electrical and thermal properties of polyvinylidene fluoride (PVDF) pyroelectric detectors is discussed. It is shown that both the dielectric constant and the thermal diffusivity exhibit a monotonically increasing behavior with the poling field. The detectors were fabricated by solution casting of the PVDF films followed by thermal poling. It is concluded that the predominant crystal phase present in our films is the γ-form. Except for the dielectric breakdown field, all the electrical and thermal properties of these films were found to be in good agreement with the commercially available ones. The thermal diffusivity was measured using the so-called open photoacoustic cell method.