Papers by Keyword: PVDF

Abstract: The polyvinylidene fluoride (PVDF) nanofiber has widely investigated as a sensor and transducer material, because of its high piezo and Ferro electric properties. The novel nano structure of PVDF has attracted considerable interest in the bio sensing and biomedical application. This paper deals with PVDF Tactile sensor. Basically The PVDF acts as piezoelectric effect which convert load into electrical signals. The tactile sensor has a main role for visual handicap and robotics. Any physical activities of robotic in all industrial the tactile sensor is a crucible role, whether it can left the object or handling glass parts pressure of object is main. The Sandwich type PVDF base tactile sensor has been fabricated using nanofiber. Using electro spinning method, the PVDF based nanofiber coated over coper the electrodes. In normal, the PVDF has α-phase and while applying electric pulse the PVDF polymer would be changed from α-phase into β-phase. Only in β-phase, the PVDF act as piezo electrics sensor and measure the piezoelectricity simultaneously measure pressure and temperature in real time. The pressure was monitored from the change in the electrical resistance via the piezo resistance of the material. The enhancement of PVDF properties has been carried by using SEM. The SEM image result showed that the size of nanofiber, the size of nanofiber is varied in the range of (180 nm-400 nm) with smooth surface. The X-Ray diffraction has shown that the PVDF was aggregated with the β-phase crystalline nature. Due to β-phase it was act as a piezo electric prosperity’s and its results are very high sensitivity.

Abstract: This article deals with selecting the appropriate method of measurement water vapour diffusion through nanofibre textiles. Parameter for comparison of different sheet materials for its ability to brake the water vapour is a equivalent air layer thickness value S_d. The equivalent air layer thickness S_d [m] expresses the equivalent air layer thickness of the air layer, which would have the same diffusion resistance as the thickness of the measured material. It is necessary to choose the appropriate measurement method for determining the value S_d with diffusion open materials such as nanofibre materials. This article compares the outcomes of two measurement methods – Dry Cup Method and Tube Method. The measurements were carried out on a sample from nanofibre textiles based on PVDF.

Abstract: In this study, Polyvinylidene fluoride (PVDF) ultrafine fibers was fabricated by electro spinning equipment using rotating collector drum with different weight percentage of multi-walled carbon nanotube (MWCNT). The fabricated PVDF-MWCNT fiber has embedded to a glass fiber reinforced polymer (GFRP) for structural health monitoring of composite structures. GFRP is non-conductive material. However, by adding (or) embedding conductive PVDF-MWCNT nanocomposites, measuring its relative electrical resistance can be achieved. This study assesses the use of piezo resistive effect and conductivity of carbon nanotubes (CNT) for in-suit measurement of electrical resistance measurements and strain measurement of carbon fiber are correlated for sensing and damage monitoring purpose. The PVDF-MWCNT fiber and PVA-MWCNT fiber embedded in GFRP were evaluated and compared. Its first time PVDF-MWCNT fiber is used in composite material for sensing the damages; hence embedded sensor will downgrade the fatigue life of the composite structures usually, but in this investigation PVDF-MWCNT focus on not to downgrade the material’s mechanical properties. The manufactured specimens were subjected to various incremental loading and unloading tensile test. During mechanical loading and unloading processes the corresponding electrical resistance was monitored simultaneously, to assess the damage level in the structure.

Abstract: This paper presents the results of experimental work on thin piezoelectric polyvinylidene fluoride (PVDF) film, used as active layer in piezoelectric transformer. PVDF film was deposited by spray deposition technique on flexible polyethylene terephthalate (PET) substrate and its thickness was measured to be 2 μm. Aluminum (Al) bottom and top contacts were deposited by vacuum thermal evaporation. The transfer function of the transformer was measured at different frequencies in the range 50 Hz – 4 MHz. It was observed that at input frequency of 1 MHz, the transfer function started to decrease, which supposed low-frequency AC/AC transformer. Dielectric losses, which characterize piezoelectric devices’ quality, were less that 0.09 in the whole frequency range. This is proof for the efficient energy conversion and stable operation of the microstructure. The work shows that the PVDF transformer performance is comparable to the existing piezoceramic based transformers, which however suffer of high dielectric losses, signal distortions and relatively low boundary frequency.

Abstract: In this work we represent the results for the development of proton conductive membranes by radiochemical modification of thin PVDF films with their subsequent sulfonation. Radiation source were ⁴He ions with energy of 27 MeV produced by cyclotron R-7M the FTI TPU. The results of IR-spectroscopy, gravimetric analysis and microscopy are represented to evaluate changes in membranes properties. It was shown that the deepness of modificated gel can be controlled by radiation.

Abstract: Polyvinylidene fluoride (PVDF) membranes were prepared with different compositions of SiO2 nanoparticles. PVDF is one of the most widely used in membrane technology. The molecular structure of PVDF fluoropolymer provides high chemical resistance, good mechanical properties and thermal stability. It also can be used as composites with inorganic nanoparticles such as SiO₂ to improve the performance and properties of the membrane. In this study, Dimethylacetamide (DMAc) was used as solvent. The prepared membranes were characterized using contact angle measurements with water, atomic force microscope (AFM) and scanning electron microscope (SEM) for the structures of the membranes and mechanical strength. The experimental results showed that additional of nanoSiO₂ will exhibit different characteristic on the microstructure and mechanical strength of the membrane.

Abstract: This study employed 7 weight percent (wt.%) of untreated and treated MgO nanofillers incorporated into PVDF polymer. The effects of coupling agents (chlorotrimethylsilane and triacetoxyvinylsilane) on the polymorphism of PVDF/MgO nanocomposite were investigated. The PVDF/MgO nanocomposite thin films of untreated and treated MgO nanofillers, with and without the addition of coupling agents were produced via spin coating technique. The average thickness recorded for these films was 300 nm thick. ATR-FTIR was conducted to investigate the changes in polymorphism of PVDF/MgO nanocomposite thin films. The results shows that PVDF/MgO (Chlorotriemethylvinylsilane) indicates better compatibility than PVDF/MgO, with sharp and distinguished absorption band at 840 cm^-1, indicating high content of PVDF, β-crystals.

Abstract: Differential scanning calorimetry (DSC) measurement is used to investigate the nonisothermal crystallization behavior of poly (vinylidene fluoride) (PVDF)/polysulfone (PSF)/diethylene glycol dibenzoate (DEDB)/dibutyl phthalate (DBP) system via solid-liquid (S-L) phase separation during a thermally induced phase separation process. The effect of benzene ring in PSF on PVDF crystallization for PVDF/PSF/DEDB/DBP system is investigated. It is found that the Ozawa model can describe nonisothermal crystallization behavior of PVDF/PSF/DEDB/DBP system in a certain crystallization temperature range. Jeziorny method indicates that the secondary crystallization of PVDF exists in the process of nonisothermal crystallization and is enhanced by the increase of cooling rate.

Abstract: On an example of poly(vinylidene fluoride - trifluorethylene) ferroelectric polymer we have shown how different optical methods can be applied for basic optical constants such as refractive index and absorption coefficient obtaining, scattering surface quality control, spectral transmission range control, examining polarization degree etc. Wide range of these methods can be applied not only to thin ferroelectric films but for other different samples.

Abstract: In this paper composite nanofiber membranes were prepared by electrospinning technology from poly (vinylidene fluoride) (PVDF)-poly (methyl methacrylate) (PMMA)-SiO₂ blend solutions with different PMMA and SiO₂ contents. It was found that the diameter of electrospun nanofibers was greatly increased with the added PMMA content but decreased with the added SiO₂ content, and when both PMMA and SiO₂ were added the diameter of electrospun nanofibers was decreased. With a proper ratio of the PMMA and SiO₂ added, the electrospum nanofiber membrane could have a suitable diameter with high porosity. The XRD results revealed that electrospun nanofiber membranes contained mainly β-phase crystal structure of PVDF, and its crystalline is reduced with the added PMMA and SiO₂ contents due to the inhibited crystallization of the polymer by the inorganic particles and PMMA during the solidification process. These nanofiber membranes exhibited a high electrolyte uptake, around 300%. Moreover, the incorporation of PMMA and SiO₂ into the nanofiber membrane improved the ionic conductivity from 1.7×10⁻³S/cm to 2.0×10⁻³S/cm at room temperature. Compared with commercial film PE, their cell cycle and charge and discharge performance were also greatly improved.