Dielectric and impedance spectroscopy studies on sisal fibre-reinforced polyester composite

Frequency and temperature dependence of dielectric constant (er), dielectric loss (tanδ), ac conductivity (σac) and complex impedance spectroscopy studies on cured polyester matrix and sisal fibre-reinforced polyester composites (SFRPC) have been investigated in the frequency range from 180 Hz to 1 MHz and temperature range from room temperature to 200 °C. The experimental results showed that with the incorporation of sisal fibre, the values of er, tanδ and σac are increased. It is also found that the values of er and tanδ for both cured polyester matrix and SFRPC are decreased with increasing frequency, which indicates that the major contribution to the polarization may come from orientation polarization and interfacial polarization. The increasing value of er with increasing temperature at a particular frequency is due to free motion of the dipole molecular chains within the cured polyester matrix and SFRPC at higher temperature.