Dielectric relaxation spectroscopy in the high-impact polystyrene/titanium-dioxide composite films

The relaxation processes in high-impact polystyrene (HIPS) films filled with titanium dioxide (TiO2) of the rutile modification have been investigated by means of dielectric relaxation spectroscopy (DRS) supplemented by differential scanning calorimetry (DSC). Films with 2, 4, 6 and 8 vol.% TiO2 were compared to each other and to unfilled samples. Above the glass transition one relaxation became visible for unfilled HIPS. It could be identified as the α relaxation, related to the onset of micro-Brownian motions at the glass transition. The low-frequency (LF) process (which superimposed with α relaxation near Tg) was observed in all TiO2 containing films. The LF process for composite films was not uniform and showed Arrhenius behavior. At lower temperatures (up to about 130 °C) an activation energy of 1.1 eV was found, whereas in the limit of high temperatures, and particularly for higher TiO2 content the activation energy was 2.4 eV.