Polyvinyl Formal Films Research Articles

Enhanced Quality Factor of Polyvinyl formal (PVF) Based Nanocomposites Filled with Zinc Oxide and Carbon Black Nanoparticles for Wireless Sensing Applications

The present article deals with the preparation of polyvinyl formal based nanocomposites filled with zinc oxide (ZnO) and carbon black nanoparticles using colloidal blending technique. To explore the electrical and structural properties, PVF/ZnO/CBNP nanocomposite films were characterized using Fourier transform infrared (FTIR) spectroscopy, X- Ray diffraction (XRD) and Scanning electron microscopy (SEM). The surface morphology of these nanocomposite films was evaluated using polarized optical microscopy (POM). The structural change in PVF nanocomposite was achieved by incorporating ZnO and CBNP, by homogeneous distribution in polymer nanocomposite. The electrical properties such as impedance and quality factor (Q – factor) of PVF/ZnO/CBNP composite films were elucidated using impedance analyzer in the wide range of frequency from 50 Hz – 20 MHz and temperature in the range 50°C – 150°C. Quality factor was measured as a function of temperature (50 – 150°C) and wide range of frequency from 50 Hz - 20 MHz. The PVF/ZnO/CBNP nanocomposite exhibits high Q-factor (439) for neat PVF films. The incorporation of ZnO at 10% decreases Q-factor to 36.1. Incorporation of CBNP at 5% and ZnO at 5% further reduces the Q-factor to 13.7. With further increase in CBNP content, the Q – factor was found to decrease7.38. Impedance values of PVA/ZnO/CBNP nanocomposites varied at different filler loading in PVF at 3% of CBNP (3.54 X 107Ω) to 10% of CB (1.48 X 107Ω). Increase in the CBNP wt% in PVF shows enhanced conductivity. Thus, based on the above results the PVF/ZnO/CBNP nanocomposites can be used for high – k capacitor applications and also for wireless sensing applications.

Transient and thermally stimulated depolarization currents in polyvinyl formal films

AbstractTransient currents in double‐sided vacuum aluminized polyvinyl formal (PVF) film samples of thickness 40 μm were investigated in the charge and discharge modes at different temperatures and fileds. The results observed suggest that the transient currents are governed by charge injection processes leading to space charge effects. Comparative studies of the isochronal characteristics (i.e. current–temperature plots at fixed times) with the thermally stimulated discharge current (TSDC) indicated a strong resemblance between the two techniques. These studies suggest that the simultaneous mechanism of movement of charges through microscopic distances coupled with dipolar orientation may be responsible for the TSDC peak observed at 100°C.

DETECTION LIMIT FOR A VERY THIN BACKING FILM

Detection limit for thin backing films is formulated. A polyvinyl formal film of ~ 0.14µm was bombarded with 3 MeV protons and continuos backgrounds were measured with a Si(Li) detector. A large constant background of a high energy region (≥6 keV ) was interpreted as the Compton tail due to the 440 keV γ-rays from the excited state of 23Na which contaminated the surface of a carbon collimator placed just in front of a target. The detection limits of this thin film, under the condition of the beam spot size 6 mmϕ without collimator, are estimated for the elements of atomic number Z=10~55 and the minimum detection limit is calculated to be 4×10−12 g for Z=28~34.

Stark effect and spectral hole-burning: solvation of organic dyes in polymers

Spectral hole-burning studies of nile red and cresyl violet in polyvinylbutyral and polyvinylformal films have been performed. From the shape of spectral holes under the influence of an electric field, the dipole moment difference between the ground and excited state of both dyes has been determined. The Stark effect was investigated at different positions in the inhomogeneously broadened absorption band of the guest molecules. The observed dipole moment difference decreases with increasing wavelength. This variation is caused by the matrix induced dipole moment. For nile red, which is a neutral and polar molecule, the distribution of induced dipole moments is strongly correlated with the orientation of its ground state dipole moment. In the case of cresyl violet perchlorate, which is a salt, this distribution is anisotropic for guests absorbing in the blue part of the inhomogeneous band but becomes more isotropic as the absorption wavelength increases. The wavelength dependence of the observed dipole moment is much stronger and is ascribed to the existence of the cresyl violet perchlorate salt in different states of solvation.

Isolation of an Iridovirus from Farm-Raised Gouramis (Trichogaster Trichopterus) with Fatal Disease

Gouramis (Trichogaster trichopterus) are a popular freshwater tropical fish raised extensively in Florida for the ornamental fish trade. Between June 1991 and February 1992, 2 separate groups of farm-raised gouramis experienced death rates of approximately 0.5-10%/day for approximately 2 weeks. About 30 diseased fish from each group were presented to the Veterinary Diagnostic Laboratory at Kissimmee, Florida. About 20 fish from each shipment survived transport and were placed in aerated aquaria and observed for 7 days; dead fish were discarded. Most infected individuals appeared clinically healthy and maintained good appetites. However, adults developed patches of hyperpigmentation and lethargy 24-96 hours prior to death, and about 30% of affected juveniles and adults exhibited abdominal distention. Approximately 70% of the fish died during the observation period, and the remaining moribund fish were killed. Necropsy of 5 individuals from each group revealed splenomegaly (2-fold greater diameter than normal) with reddening of the adjacent intestine. Clear amber fluid (0.5-2 ml) was present in the coelomic cavities of the fish with distended abdomens. Attempts to culture bacterial pathogens from spleens and kidneys on tryptose blood agar plates were unsuccessful. Ultrastructural examination was performed on pellets harvested from tissue homogenates and on ultrathin tissue sections. Samples included spleen, anterior kidney, liver, and intestine; 1 heart sample was processed for epoxy sections only. To obtain pellets, unfixed tissues were homogenized in deionized water (10% w/v) and then centrifuged at 4,000 x g for 10 minutes. The supernatant was centrifuged at 14,000 x g for 60 minutes. The resulting pellet was suspended in 25 µ1 deionized water, mixed with an equal volume of 1.5% phosphotungstic acid (pH 6.8), and applied to grids covered with carbon-coated polyvinyl formal film a using a micropi

PREPARATION OF THIN SUPPORT FILM FOR PIXE AND ITS APPLICATION TO TRACE ANALYSIS OF BIOLOGICAL MATERIALS

A thin support film is indispensable to make targets of biological material for trace analysis by PIXE. We developed a simple technique for the preparation of high quality support film. Polyvinylformal (PVF) was dissolved in tetrahydrofuran (THF) and the solution was spread on the surface of sucrose solution. The THF was evaporated and a PVF film formed on the surface. The thickness of the PVF film was 0.1µm with good homogeneity. The PVF film was stable to 3MeV proton bombardment and no impurity elements were observed. The continuous X-ray background was <1/20 that of 280µg/cm2 Mylar. We used the PVF film as a support film for some biological materials. Because of the lower X-ray background from the PVF film, K, Ca, Fe, Ni, Cu, Zn, As and Br in 50–100µg of biological materials could be detected.

Electrical properties of pure and iodine-doped polyvinyl formal films

The electrical properties of pure polyvinyl formal films of thickness 33.5 νm grown by the solution growth technique have been studied. Measurements of current-voltage (I-V) characteristics in the temperature range 303–413K were used to determine the conduction mechanism. It was found that a Poole-Frenkel type of conduction mechanism is dominant throughout the temperature range studied. An investigation of the effect of impurities such as iodine on the activation energies of the trap depth in the polymer matrix was also undertaken.