Dielectric spectroscopy in Silicone Rubber Incorporating Nanofillers

Dielectric isothermal spectroscopy is performed on micro composite and micro/nano composite silicone rubber in the ranges of temperature and frequency of [113-293 K] and [10^-1-10⁶ Hz] respectively. Two specimen have been studied: i) a commercial liquid silicone rubber LSR containing `micro-sized\´ fumed silica fillers; ii) the same silicone rubber in which we added 0.10 weight fraction of nano SiO_x particles. A comparison of their dielectric responses (real epsiv\´ and imaginary epsiv" parts of dielectric permittivity) is presented. For the commercial LSR without nano SiO_x, typical values of epsiv\´ and epsiv" have been obtained. As plotted against the temperature (at a fixed frequency) epsiv\´ and epsiv" present a maximum around 155 K which is attributed to the a relaxation around the glass transition. A strong relaxation peak is observed as nano particles are added in the commercial silicone rubber. The more probable phenomenon to explain this peak is the adsorption of water at the filler surface before mixing.