Abstract
Dual phase fillers of the type carbon black-silica have been prepared by two different technologies. The first one was based on mild operating conditions, the thermal activation was accomplished at a lower temperature, while in the second technology the temperature was higher and vacuum was applied. The fillers, synthesized by the two methods, differ considerably in their characteristics. The more intensive impregnation of the carbon black with silica-sol and thermal activation at higher temperature leads to better mutual penetration of the two phases and better isolation of the conductive particles of the carbon phase by the dielectric silica phase.