The influence of titanium dioxide additive on the short-term DC breakdown strength of polyethylene

The effect of the addition of I % by weight of titanium dioxide fine particles to low density polyethylene (LDPE) on the short-term d.c. breakdown strength of the LDPE was investigated using direct and reverse polarity voltages. The samples used, were cylinders of both plain and doped materials, with hemespherically tipped cylinderical electrodes completely embedded in the material, with a minimum gap length between the electrodes tips of 0.25 mm. All tests were conducted at room temperature. Results indicate that although the addition of TiO, has reduced the d.c. breakdown strength of the doped material if compared to the plain material, yet it has significantly improved its d.c. reverse polarity characteristics. The doped material seems to be insensitive to the d.c. polarity reversals. The observed beneficial effect of the addition of TiO, on the d.c. reverse polarity characteristics is attributed to the role of this additive in modifying the trapping levels in the polymer, and the consequent change in the space charge pattern in the doped material.