Low-density polyethylene (LDPE) filled with a small amount of titanium dioxide proves to be very suitable for studying the molecular motion of polyethylene by means of dielectric spectroscopy. The titanium dioxide acts as an oxidizing agent that introduces a small concentration of polar carbonyl groups, which does not alter molecular motion, but couples it to the alternating electric field. The frequency and temperature dependences of molecular-motion processes in LDPE are determined from both isochronal and isothermal loss plots. In particular, the temperature dependence of the β process connected with the glass-rubber transition in polyethylene obeys the Vogel-Fulcher-Tammann-Hesse law, which indicates co-operative behaviour. For pure LDPE, a glass-transition temperature of -31 °C is determined dielectrically. It increases with increasing titanium dioxide content.

Low-density polyethylene (LDPE) filled with a small amount (1 to 10 wt.%) of titanium-dioxide (TiO/sub 2/) powder proves to be very suitable for studying the molecular motion of polyethylene by means of dielectric spectroscopy. The titanium dioxide acts as an oxidizing agent that induces a small concentration of polar carbonyl groups, which do not alter molecular motion, but couple it to the alternating electric field, The frequency and temperature dependences of molecular-motion processes in LDPE are determined. In particular, it is shown that the temperature dependence of the /spl beta/ process connected with the, glass-rubber transition in polyethylene obeys the Vogel-Fulcher-Tammann-Hesse law, which indicates co-operative behaviour. The dielectrically determined glass-transition temperatures are close to the literature value of about -30/spl deg/C. The unrelaxed permittivity increases with TiO/sub 2/ content by a factor of 1.45 at 35 wt.% TiO/sub 2/. This is lower than expected from models for the permittivity of heterogeneous mixtures. It points towards an inhomogencous TiO/sub 2/ -particle distribution.