Kinetics of the glass transition of styrene-butadiene-rubber: Dielectric spectroscopy and fast differential scanning calorimetry

Abstract

The glass transition is relevant for performance definition in rubber products. For extrapolation to high-frequency behavior, time–temperature superposition is usually assumed, although most complex rubber compounds might be outside of its area of validity. Fast differential scanning calorimetry (FDSC) with cooling rates up to 1500 K/s and broadband dielectric spectroscopy (BDS) with frequencies up to 20 MHz are applied here to directly access both kinetics and dynamics of glass formation in a wide frequency range. For the first-time, the relation between the thermal vitrification and the dielectric relaxation is studied on vulcanized styrene-butadiene rubber, showing that both cooling rate and frequency dependence of its glass transition can be described by one single Vogel-Fulcher-Tammann-Hesse equation. The results indicate the validity of the Frenkel-Kobeko-Reiner equation. Another focus is the sample preparation of vulcanized elastomers for FDSC and BDS as well as the temperature calibration below 0°C.