Filler concentration effects on losses in silicone based polymeric composites

Silicone polymer based rubber with different concentrations of powdered aluminum trihydrate (ATH) as filler were studied. Dielectric properties χ*(ω)=χ´-iχ´´ were measured at different temperatures using low frequency dielectric spectroscopy technique. Without any ATH filler a classical interfacial relaxation was significant with dominating dc conduction in losses, χ´´. By increasing the concentration of the filler a low frequency dispersion mechanism started to dominated in the relaxation behavior. With adding the filler, the dc conduction first decreased and then increased again after a certain concentration level was passed. This behavior showed that the filler particles acted like scattering centers or traps for conduction when the concentration was low. As the concentration increased the conductivity of the filler particles and of the interface (between filler particles and the polymer matrix) started to dominate the conduction. Master curve shifts of the data also showed Arrhenius type of behavior