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

Abstract

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.