Modeling the high frequency mechanical relaxation of simplified industrial polymer mixtures using dielectric relaxation results

Abstract

The mechanical characterization of rubber materials at the frequencies relevant for the tire function during braking (about 1 MHz) is extremely challenging. On the other hand, dielectric relaxation experiments provide a suitable tool for the analysis of relaxation phenomena over a broad frequency range with high sensitivity. Here we show that by analyzing dielectric relaxation experiments in the framework of a simple model the mechanical relaxation of simplified industrial systems based on mixtures of a styrene butadiene rubber (SBR) with a polystyrene oligomer can be anticipated, at least for the SBR rich mixtures that are more relevant for development of tire polymers. The model needs the description of the dielectric and mechanical relaxation processes of the single components of the mixture and uses concepts and ideas introduced in the past for describing the segmental dynamics of athermal polymer blends. The model description of dielectric relaxation experiments on the mixtures provides a quantification of the thermal fluctuations of concentration in the blends. With this input, the mechanical relaxation of the mixtures are calculated using well established equations for the mechanical properties of composite materials. The present approach should be helpful in a rational design of the rubber material depending on the specific requirements.