The morphology of natural rubber/styrene–butadiene rubber blends (NR/SBR) was characterized by atomic force microscopy (AFM), with regard to curing temperature and curing time. The changes in blend morphology were directly visualized by AFM which confirmed the results of indirect experiments like differential scanning calorimetry (DSC). Comparing the phase morphologies at different curing temperatures indicated that the domain size of SBR increases with temperature at lower curing temperatures, but domain growing stops at the latest scorch time. This effect is explained by longer scorch times at low curing temperatures which facilitate phase separation, while the short scorch times at higher temperatures meant that the coalescence of SBR phases was hindered by cross-linking between polymer chains.

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.

Tire tread materials are generally blends of two or more rubbers, fillers, and other materials, resulting in a rubber compound with complex multiphase morphology. The bulk properties of these blends are influenced by morphology and microphase characteristics, hence the desire for techniques that can both discriminate between phases in a blend and provide quantitative information about their physical properties. The effect of polymer ratio and microstructure of SBR on blend morphology and nanomechanical mapping of unfilled NR/SBR blends will be discussed. With nanoindentation techniques available through the use of atomic force microscopy, nanomechanical properties are determined and compared with macroscopic values obtained by dynamic mechanical analysis.

The development of rheological nonlinearity of NR during aging has been investigated. • The evolution of the crosslink density and defects correlate well to rheological response. • The parameter from FT-Rheology I 3/1 exhibits higher relative sensitivity. • With the limitations of NMR and microscope, I 3/1 respond to the network change at both nano-and micrometer scales.