Dynamic mechanical analysis and dielectric relaxation spectra of carbon silica dual phase filler reinforced chlorobutyl vulcanizates were used to study their relaxation behavior as a function of temperature (-60 degrees C to +100 degrees C) and frequency (100-10(6) Hz). Strain-dependent dynamical parameters were evaluated at dynamic strain amplitudes of 0.07-5%. The nonlinearity in tan delta and storage modulus was explained based on the concept of filler-polymer interaction and the interaggregate attraction (filler networking) of carbon black. The dynamics of chlorobutyl chain segments in the composites was explained on the basis of their connectivity. The segmental relaxation of the polymer chains in the presence of filler and crosslinking has been explained, based on conformational transitions occurring at high frequencies. The 'percolation limit' of the filler in the composites was found to be in the range of 30-40 phr loading. (c) 2006 Wiley Periodicals, Inc.