Relaxation behavior of chlorobutyl elastomer nanocomposites: effect of temperature, multiwalled carbon nanotube and frequency

Abstract

Dynamic mechanical (visco-elastic) relaxation and dielectric relaxation spectra of multiwalled carbon nanotube (MWCNT) reinforced chlorobutyl (CIIR) elastomer nanocomposites were studied. The primary relaxation (α transition, the glass transition) have been studied by dynamic mechanical analysis as a function of temperature (−100 °C to 100 °C) at a frequency of 1 Hz and at 1 % strain. Irrespective of the MWCNT loading, all nanocomposites showed glass-transition temperatures in the range of −15 °C to −10 °C, which was explained on the basis of the relaxation dynamics of polyisobutylene chains in the vicinity of the fillers. The nonlinearity in the tan δ and storage modulus was explained by the concept of MWCNT-chlorobutyl interactions and the aggregation of the nanotubes. The secondary relaxation (α* or β relaxation) have been studied using dielectric relaxation spectra in the frequency range of 100–106 Hz. The capacitance of the nanocomposite was expressed in terms of dielectric permittivity and explained on the basis of polarization of the MWCNT in the chlorobutyl matrix. The electric modulus formalism has been utilized to further investigate the conductivity and relaxation phenomenon. Argand diagram confirms the existence of non-debye/non-linear relationship. The percolation threshold of was found to be at 6 phr MWCNT loading, as studied by conductivity and dielectric permittivity measurements.