Comparison of viscoelastic and dielectric relaxations as a function of carbon black loading in butyl and chlorobutyl rubber

Abstract

Dynamic mechanical and dielectric spectra have been measured for a number of the simpler amorphous polymers such as acrylate compounds. Many complex polymer systems such as synthetic rubbers have not been as extensively studied. A transfer function technique and time-temperature superposition were used to measure the frequency-dependent Young's modulus and loss tangent as a function of carbon black loading and type in chemically cross-linked butyl and chlorobutyl rubbers. Dielectric permittivity and loss were measuerd as functions of frequency and temperature. The dielectric behavior was significantly influenced by the type of cross-linking system and by filler loading. The Williams-Watts ‘stretched exponential’ function was found to be a reasonable fit to the dielectric spectra of the unfilled systems. The effects of molecular motions and rubber-filler interactions on the two types of relaxations are discussed.