Composites based on HDPE filled with BaTiO3 submicrometric particles. Morphology, structure and dielectric properties

Composites of high density polyethylene, HDPE, filled with submicrometric particles of BaTiO3, BT, have been prepared. Uniform dispersion of the particles was achieved by high energy ball milling and subsequent hot pressing. Using SEM, FTIR, TGA-DTA and stress-strain tests, studies of the structural, morphological and mechanical features of the composites have been carried out. Frequency response analysis, dielectric strength and resistivity measurements were also performed to evaluate the final electrical properties as a function of the processing and the amount of BaTiO3 particles. From the analysis of the microscopic structure, it can be deduced that any change in the properties of the materials must be solely ascribed to the presence of the BT particles. A balance between an enhancement of space charge polarization with the presence of BT and the existence of permanent dipoles associated to them might explain an initial increase in the dielectric losses with the BT content, and its later decrease at higher BT content. The observed decrease in resistivity and breakdown voltage when increasing the amount of BaTiO3 can be explained by the lower resistivity of BT particles at room temperature and the growing accumulation of space charge.