The role of BaTiO/sub 3/ in modifying the dc breakdown strength of LDPE

Abstract

In the present paper, the effect of the addition of fine particles 1%wt BaTiO/sub 3/ to plain low-density polyethylene (LDPE) on the short-term dc breakdown strength of LDPE is investigated. The Weibull plots are used to analyze the breakdown test results. This indicates that the addition of BaTiO/sub 3/ to LDPE has reduced the short-term dc breakdown strength of the doped material by /spl sim/16% and increased the dispersion of the breakdown data. The results also indicate that the Weibull exponent b has been reduced significantly for the doped material. Earlier measurements on the effects of the incorporation of BaTiO/sub 3/ in LDPE on dc current transients and space charge formation in LDPE are presented and correlated with the present results. Results from a variety of measurements using different techniques such as X-ray diffraction, differential scanning calorimeter (DSC), scanning electron microscopy (SEM), and optical microscopy are used in order to establish the effects of the incorporation of the additive in the polymer on its structure and morphology. The multiple role of BaTiO/sub 3/ additive in modifying the dc breakdown strength of LDPE is discussed in general terms of the existing breakdown theories in solid dielectrics. The combined effects of the additive on the different factors which influence the breakdown process in solids such as charge carrier mobility, charge carrier injection at the electrodes, space charge formation, polymer structure and morphology is explained and discussed. The present work introduces some novel elements in explaining breakdown processes in polymeric solid dielectrics by using an additive of known effects to provide an insight into the breakdown in LDPE. Moreover, an attempt is made to integrate results from different measurements using a multitude of techniques to yield a meaningful picture of the breakdown mechanism of LDPE.