Thermomagnetic stability and heat-resistance properties of carbonyl iron filled siloxanes

This paper focuses on the investigation of the frequency-temperature dependence of the complex permeability and permittivity of polydimethylsiloxane (PDMS) filled with carbonyl iron (CI) powders. The investigation is aimed at the development of thermally stable polymeric magnetic materials. It is established that, in contrast to the magnetic properties, which vary little up to temperatures of 150 °C, the dielectric properties exhibit appreciable variation with increasing temperature. As temperature increases, composites with primary CI show much smaller decrease in permittivity compared with composites based on processed CI, because the onionlike particle structure of primary CI is more stable to high-temperature oxidation. The influence of CI on the thermal destruction of PDMS is attributed to the chemical composition and the surface behaviour of CI particles. It is established that among all investigated types of CI, only processed CI enriched with α-iron have a temperature stabilizing effect on composite materials, which is associated with the inhibition of depolymerisation of PDMS.