Space charge and electrical conductivity in LDPE doped with titanium dioxide

DC conductivity and space charge density were measured in 1mm thick samples of polyethylene with density 0.885 g/cm³ and approximately 17% crystallinity. 2 wt % of the rutile form of titanium dioxide was added to some samples, and 2 wt % of the anatase form to others. Current measurements using semiconductor electrodes were made in the temperature range 40-80 °C, and at applied dc voltages of 20 and 40 kV. The effect on the conductivity of holding the samples at 70 °C and 3-4 × 10^-2 mbar for several days before commencing measurements was also investigated. Space charge density measurements were made at 20 and 30 °C, and at 20 kV, using the LIPP technique and semiconductor electrodes. The effect of a temperature gradient on the space charge profiles was also investigated.