Dielectric Spectrscopy Analysis Behavior of low Density Polyethylene

Abstract

Dielectric spectroscopy is a powerful tool in the investigation of dipolar and conduction in electrical insulating materials. In particular, the localisation of space charges at crystalline - amorphous interfaces in a semicrystalline polymer, such as low density polyethylene LDPE, provides on internal field which could be unfavourable to the insulating properties of the polymer. A physical displacement of space charges through the clusters and structural defects can be detected in the low frequency region. Changes in the real and imaginary parts of the complex permittivity correspond ot changes in the bulk capacitance and conductance of the polymer. In this work we have presented results of dielectric studies in semicristalline polyethylene low density by means of dielectric relaxation spectroscopy (DRS) in frequency range 10-3 - 106 Hz and temperature between -60 and 70degC In this study a relaxation is observed at high frequencies as a large peak in the domain 1 Hz - 10 kHz in the plot of the imaginary part of dielectric permittivity epsiv* (omega) and in the plot of the loss factor Tandelta(omega). An important increasing in values of epsiv and Tandelta at low frequencies and high temperature is observed. Also it was noted that the effect of electrical conductivity causes an important increasing in the index of losses epsiv(omega). The dielectric permittivity epsiv' presents a gradual decrease with increasing frequency and increasing temperature. This feature is masked by high index losses epsiv values due to DC conductivity.These results confirm that the step in the permittivity epsiv'(omega) is due to conductivity current relaxation.