Conductivity Of Polyvinyl Alcohol Research Articles

Comparative Analysis of Dielectric Properties of Polyvinyl Alcohol and Polyethylene

The article presents a new comparative analysis of the dielectric properties of polyvinyl alcohol (PVA) and polyethylene (PE) at different temperatures and their other physical properties. The characteristic peaks were observed in the FTIR spectra of the polymers. The amounts of carbon and oxygen on PVA’s surface differed from PE. It was hypothesized that these properties could be affected by the increase in temperature and difference in the chemical structures of the polymers. We investigated the dielectric properties of these polymers between 20 °C and 100 °C. Our results revealed that the dielectric properties of these polymers were not the same. The actual permittivity values of PVA at low temperatures were almost constant for all frequency values and increased at higher temperatures with the decrease in frequency. The same pattern concerning the increase of imaginary permittivity of this polymer was observed at low frequencies. The increase of the real and imaginary permittivity of the PVA accompanied the increase in temperature. The actual permittivity of PE was almost constant with the frequency at different temperatures. However, the imaginary permittivity of this polymer showed an increase at low frequencies. The increase in temperature accompanies the increase of the PE’s imaginary permittivity. As expected, the capacitance, like permittivity, changed differently for the polymers. Moreover, an increase in temperature had more effect on the conductivity of PVA than that of PE. The difference in these polymers’ dielectric properties could be due to their chemical structures. The results of this article can be used for further applications of PVA and PE in science and engineering.

PVA biopolymer-acidic functionalized graphene hybrid nano composite for vibration isolation application: An experimental approach with variable reflux and vacuum timings

In this research work, polyvinyl alcohol (PVA)-graphene (Gr) nano composite films were fabricated by incorporating the functionalized graphene (f-Gr) for different periods of refluxing and vacuum oven time. The graphene particles were functionalized through nitric acid (HNO3). Various tests were conducted to estimate the properties and characteristics of this composite. Fourier transform infrared spectroscopy (FTIR) results confirm the bonds of carboxyl, hydroxyl and carbonyl groups, manifested of functionalization of graphene. Scanning electron microscopy was performed to investigate morphology and transparency of f-Gr nano-particles in nano-composite films. Water absorption test was carried out to evaluate water absorption (%) in the PVA based composite films. The result revealed that water absorption rate of the composite decreased with increasing refluxing time at constant vacuum oven time of f-Gr reinforced composite. Dynamic mechanical analysis (DMA) showed that the value of storage modulus was higher for PVA-f-Gr nano-composite films compared to neat PVA and PVA-Gr composite over the entire range of temperature, which lead to explore this composite material for the vibration isolation applications. Glass transition state (Tg), loss modulus and the damping factor (tan δ) of the PVA-f-Gr nano composites films were highly affected by the addition f-Gr nano crystals in the PVA matrix. The value of tan δ for f-Gr nano composite is obtained both higher as well as lower compared to PVA-Gr film for the varying vacuum oven time and refluxing time. Electrical analysis indicates an enhancement in conductivity of PVA with introduction of f-Gr nano particles. After evaluating the high damping characteristics of this composite, the authors perceive that it may be utilized to reduce noise transmission and as a shock absorber vibration isolator.

Ratio and Temperature Dependence of Dielectric Properties and AC Conductivity of Polyvinyl Alcohol / Iraqi Eggshell Composites

The polymer composites used in the present study were made of polyvinyl alcohol (PVA) as a matrix and Iraqi eggshell powder as filler. The eggshell powder was obtained from the waste of Iraqi chicken eggshell. The solution-casting method was used to prepare PVA/eggshell powder composite films with ratios (10, 30, and 50 wt %) of eggshell powder. The dielectric properties (dielectric constant, and power factor) and AC conductivity were investigated in the frequency range 100 kHz to 5 MHz at room temperature and different temperature (50, 70, 90, and 110 oC). It was found that the PVA sample and PVA samples containing 10% and 50% of eggshells had a dielectric constant that increases slightly with frequency up to 200 kHz, after which the decrease in the dielectric constant was very slight. While the sample of PVA containing 30% eggshell powder, the dielectric constant decreased slightly with increasing frequency. By studying the behavior of dielectric constant as a function of eggshell additives it was fond that the sample containing 50% of the eggshell powder has lowest values of the dielectric constant while the sample containing 10% of the eggshell powder has the highest values. The power factor decreased at a very small rate with increasing frequency and generally, the addition of eggshells led to a decrease in the power factor. At frequencies greater than 1MHz, it was found that the sample containing 10% eggshells has the highest conductivity while the samples containing 30% eggshells has lowest values. About the effect of temperature on the studied properties it was found that the dielectric constant and power factor generally increased with increasing temperature. Also, the values of the dielectric constant for samples containing 50% eggshell powder were lower than the other samples. It is generally found that the conductivity increased with frequency. At different temperatures it was found that sample containing 10% eggshells powder has close values of electrical conductivity. Generally, the samples had the highest conductivity at a temperature of 110 oC.

ВИКОРИСТАННЯ ГУМІНОВИХ КИСЛОТ ДЛЯ МОДИФІКАЦІЇ БІОДЕГРАДАБЕЛЬНИХ ПЛІВОК, ВИГОТОВЛЕНИХ НА ОСНОВІ ПОЛІВИНІЛОВОГО СПИРТУ ТА ГІДРОКСИПРОПІЛМЕТИЛЦЕЛЮЛОЗИ

The article is devoted to the problem of obtaining packaging materials that combine a high level of gas and / or moisture resistance and strength with the ability to quickly decompose without harmful effects on the environment. The purpose of the research described in the article is to study the possibility of making such a material, which, during the period of use, will not only be resistant to the effects of various bacteria, but even prevent their appearance, and upon burial it will be biodegradable. The initial components, namely polyvinyl alcohol, hydroxypropyl methylcellulose, and humic acids of coal origin (as antibacterial additives) were reasonably selected. The modifying effect of humic substances obtained from three different samples of low-grade Ukrainian coal has been studied. In the course of the studies performed, it was found that humic acids of different origins and with different characteristics have a specific effect on the processes of structure formation in solutions of polyvinyl alcohol and hydroxypropyl methylcellulose. In particular, it was shown that in polyvinyl alcohol and methylcellulose solutions with the addition of humic acids that do not contain particles of carbon residues of various degrees of dispersion, an increase in the formation of an ordered structure is observed. Micrographs of solutions of polyvinyl alcohol and hydroxypropyl methylcellulose with humic acids are presented. The peculiarities of the influence of humic substances on the processes of structure formation of solutions of polyvinyl alcohol and hydroxypropyl methylcellulose have been investigated in order to obtain hybrid environmentally friendly biodegradable polymer films. The corresponding experimental-statistical mathematical models have been developed, they describe the dependence of the conditional viscosity and conductivity of polyvinyl alcohol and hydroxypropyl methylcellulose on the content of humic acids, the duration of preparation and one of the characteristics of the raw materials used to obtain humic acids. The corresponding equations are given. Keywords: biodegradable polymer films, coal, humic acids, polyvinyl alcohol, hydroxypropyl methylcellulose, experimental statistical mathematical models Corresponding author Zhang Siaobin, e-mail: shefuqinke1992@gmail.com

Effect of zeolite content on proton conductivity and technical characteristics of the membranes based on crosslinked polyvinyl alcohol

Polyvinyl alcohol (PVA)-based ion-exchange membranes are a promising group of materials for use in solid polymer fuel cells (SPFC) due to their high hydrophilicity, film forming ability, low cost, good mechanical properties and the possibility of crosslinking PVA with various chemicals. The compounds with a carboxyl or carbonyl functional group, such as polybasic acids and their anhydrides, were used as crosslinking agents resulting in the formation of a gel. Cross-linking reagents may contain ionic groups, for example, sulfonic, inducing the proton conductivity of PVA in membranes. Ceramic materials based on the oxides of aluminum, silicon, titanium, tin, zirconium, etc. serve as dopants in order to improve the technical characteristics of such membranes, such as to increase ionic conductivity, chemical and thermal stability, as well as the mechanical strength of the membranes. In this work, we report on the preparation of new biodegradable proton exchange membranes for SPFCs based on of polyvinyl alcohol crosslinked with sulfosuccinic acid and doped with beta zeolite particles. The content of zeolite in the composition of the membranes was varied from 1 to 25 %. The effect of the zeolite content on proton conductivity, ion-exchange capacity, moisture content, swelling coefficient, fuel (methanol) permeability and mechanical properties of membranes was studied. An increase in zeolite content from 1 to 25 % leads to an increase in the ion-exchange capacity of membranes from 1.5 to 2.9 mmol/g, a decrease in moisture content from 38 to 28 % and a methanol permeability from 2.27  10 -6 to 6.91  10 -7 cm 2 s -1 . The temperature dependence of the proton conductivity of composite membranes in the range from 30 to 80 oC at the relative humidity of 100 % was studied. The highest value of electrical conductivity was demonstrated by a membrane containing 25 % of BEA zeolite, whose proton conductivity was 23.2 mS·cm -1 .

Enhancement of Thermal Conductivity of Polyvinyl Alcohol Membrane Using Nano-fiber

ABSTRACTThe thermal properties of organic membranes attract much attention due to the fact that heat dissipation in electronic devices limits their functionality and reliability. Here, we enhance the thermal conductivity of polyvinyl alcohol (PVA) membrane using nano-fibers fabricated by electrospinning. Measured by the 3-Omega method, the results show that the effective thermal conductivity of the electrospinning membranes (with/without Cu nanoparticles) are as high as 0.7 W/m-K at room temperature which is as twice as the value of thermal conductivity of amorphous spin-coated PVA membrane (0.35 W/m-K). The mechanism of enhancement are that, compared with amorphous membrane, the phonon scattering is attenuated and the crystallinity is improved in the electrospinning process. Our studies bring new insights in designing new kind of membrane with high thermal conductivity.

Functionalized SiC nanocrystals for tuning of optical, thermal, mechanical and electrical properties of polyvinyl alcohol

Polyvinyl alcohol (PVA)-SiC nanocomposite films were prepared by incorporating functionalized Silicon Carbide (f-SiC) nanocrystals in PVA matrix. Structural characterization of SiC nanocrystals before and after the functionalization was carried out using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Thermogravimetric analysis (TGA). Transmission electron microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to study the morphology and size distribution of f-SiC nanocrystals in PVA-SiC nanocomposite films. TEM and SEM images depict an improved dispersion of f-SiC nanocrystals in PVA matrix. UV–Visible absorption spectroscopy was employed to study the optical properties such as absorption coefficient (α), optical energy gap (Eg), Urbach's energy (Eu), refractive index (n) and dielectric constant of PVA and PVA-SiC nanocomposite films. Refractive index of PVA, at 550nm wavelength, increased from 1.7 to 2.2 for PVA-SiC nanocomposite film containing 0.023wt% f-SiC nanocrystals. TGA shows that the onset of thermal decomposition of PVA is only slightly affected by the addition of f-SiC nanocrystals. Knoop microhardness number has increased from 23MPa for PVA to 45MPa for PVA-SiC nanocomposite film containing 0.023wt% f-SiC nanocrystals at an applied load of 9.8mN indicating improved interfacial interaction. Current-voltage analysis indicated an increase in conductivity of PVA with the introduction of f-SiC nanocrystals. The conduction mechanism responsible for charge transport in PVA-SiC nanocomposite films was found to be voltage dependent. Schottky mechanism is the dominant conduction mechanism at high voltages whereas Poole Frenkel mechanism dominates at low voltages.

Synthesis and effect of vanadium pentoxide nanoparticles on dielectric relaxation and ac conductivity of polyvinyl alcohol

The dielectric parameters of polyvinyl alcohol containing 0–0.8 wt. % vanadium pentoxide are studied in the temperature range 20–150 °C at different frequencies: the dielectric constant, dielectric losses, and tangent of the angle of dielectric losses. Cole–Cole plots are used to determine the static dielectric constant and the dielectric constant at infinitely high frequency. The relaxation time is determined at different frequencies as a function of the tangent of the angle of dielectric losses versus the temperature. It is found that the relaxation properties follow the Arrhenius equation, the activation energy decreases with the vanadium pentoxide content in polyvinyl alcohol. An investigation of the dielectric relaxation as a function of temperature at constant frequency revealed two types of relaxation processes: dipole-segmented motion (α-relaxation) and side-chain dipole group motion (β-relaxation). The ac conductivity in the system polyvinyl alcohol––vanadium pentoxide is explained on the basis of the correlated barrier hopping model.

Optimization and photophysics of cadmium selenide nanoparticles

CdSe nanocrystallites of different sizes were prepared in polyvinyl alcohol (PVA) photopolymer films. Particle sizes were optimized by variation in the Cd to Se ions ratio up to 16:1 as well as doping in PVA. X-ray diffraction shows that the degree of crystallinity of PVA was found to decrease due to doping with CdSe NPs and having a cubic unit cell. The UV–vis absorption spectra for the CdSe NPs in both solutions and PVA films showed blue shifts with increasing the ratio of Cd ion leading to the decrease of the particle size. The photoluminescence spectra resulting from 441.5 nm He–Cd excitation of CdSe NPs in PVA show the same behavior of absorption spectra. A blue shift in most of the FT-IR and FT-Raman bands of PVA was observed due to the interaction between PVA and CdSe NPs, which increase by decreasing the particle size. The conductivity of PVA was found to increase by decreasing the particle size of CdSe NPs.

Preparation and conductivity of polyvinyl alcohol (PVA) films composited with molybdotungstovanadogermanic heteropoly acid

In this work, the polyvinyl alcohol (PVA) films composited with molybdotungstovanadogermanic heteropoly acid were prepared. Infrared spectra (IR) revealed that the Keggin structure characteristic of the GeMo 2W 9VO 40 5− anion was present in PVA films. At room temperature (20 °C), the conductivity of the samples of different HPA content increased from 2.46×10 −3 to 9.92×10 −3 S cm −1. The results indicated that they are new kind of excellent high-proton conductor.

Frequency and temperature dependencies of a.c. conductivity of polyvinyl alcohol (PVA)-CoCl2 composites

The a.c. conductivity for polyvinyl alcohol (PVA)-CoCl2 composites prepared by a casting method has been measured at different frequencies (0.1–10 kHz) in the temperature range 300–450 K. At constant temperature, the frequency dependence of a.c. conductivity, Σ(Ω), was found to fit the established equation Σ(Ω) = AΩ s quite well. On the other hand, the temperature dependence of a.c. conductivity suggested an electronic hopping conduction mechanism in a thermally assisted electric field. Various theoretical mechanisms have been discussed to clarify the conduction processes in these samples. The correlated barrier hopping (CBH) mechanism, proposed by Elliott, was found to be the most appropriate one.