Maxwell–Wagner–Sillars relaxations in polystyrene–glass-bead composites

The Maxwell–Wagner–Sillars (MWS) relaxation is studied for glass-bead–polystyrene (PS) composites having compositions from 0% to ∼50% in volume, in the range 20 Hz–1 MHz and for temperatures varying from room temperature to 280 °C. For the PS matrix, the complex permittivities and ac conductivities are within the limits of 3.3–3.7 and 2–3×10−9 Ω−1 cm−1, respectively, at 1 kHz in a 120–180 °C temperature interval. For the glass, these parameters vary between 20 and 300 for the complex permittivity, and between 9×10−9 and 4×10−8 Ω−1 cm−1 for the ac conductivity, in the same conditions. Good agreement is found between the calculated values of the maximum loss factor frequencies and the experimental ones. The relaxation found in the composite at temperatures above the α relaxation of the PS is ascribed to the trapping of conductive carriers at the interface between the glass spheres and the polymer matrix. This MWS relaxation is showed to have an activation energy of 20 kcal mol−1 and a relaxation time of 10−13.6 s. From the Argand representations it is observed that the MWS phenomenum deviates from a simple Debye-like process for composites having glass volume fractions from 12.5% upward.