Effect of Barium Titanate (BaTiO3) Additive on the Short-Term DC Breakdown strength of Polyethylene.

The use of additives to insulating materials is one of the methods to improve certain properties of these materials. Additives can also be used to provide more insight into some precesses like conduction, space charge formation and breakdown under certain conditions of field application. In the present paper, the effect of the addition of fine particles 1 wt% BaTiO₃ to plain low density polyethylene (LDPE) on the short-term dc breakdown strength of LDPE at room temperature was investigated. The characteristics of the used polyethylene are as follows: density 0.925 g/cm³, melt index 0.25 g/10 min. The BaTiO₃ used was laboratory grade with particle size less than 7 μm. Special cylindrical test samples of both undoped and doped materials were used in this investigation. Stainless steel hemispherically tipped electrodes were embedded in the material by moulding. The mean value of the gap length between the electrodes was 0.25 mm. The design of the test sample allows for determining the intrinsic breakdown strength of the material. The Weibull plots were used to analyze the breakdown test results. Analysis of the results indicate that the addition of BaTiO₃ to LDPE has reduced the short term dc breakdown strength of the doped material by about 16% if compared with the corresponding value for the plain LDPE. An attempt is made to correlate between the present results, and earlier published results about the effect of BaTiO₃ on dc conductivity and space charge formation in LDPE.