Theoretical and morphological evaluation of dynamic viscoelasticity and thermo-mechanical characteristics of TPV composites

Abstract

In this work, the regular usage of conventional dynamic mechanical analyzer (DMA) has been extended through the characterization of rubber elasticity and dynamic viscoelasticity of the TPV composites based on natural rubber, ethylene octene copolymer and carbon black (NR/EOC/CB). Two independent theoretical approaches viz. rubber index and damage parameter, have been adopted in order to evaluate the same. Rubber index, which is the function of temperature and entropy, has been utilized here to estimate the elasticity of the rubber networks. On the other hand, a classical damage parameter, which is a measure of dynamic viscoelasticity, has been obtained from initial tangent modulus through cyclic stress softening i.e. Mullins effect. Moreover, the measurement of thread break-up time obtained from the capillary number expression and morphological observations has directed us to revalidate the new mechanism of morphology evolution through the thermodynamic calculations. The reduced interconnectivity between the rubber domains, which has been obtained as a result of uneven filler dispersion into the rubber phase, has resulted in reduced elasticity in the rubber networks, as evident from the experimental results and atomic force micrographs. This study has thus revealed different novel aspects of dynamic mechanical analyzer and provided innovative methods for the characterization of rubber-like materials.