Determination of the Crosslink Density of Tire Tread Compounds by Different Analytical Methods

The crosslink density of rubber compounds influences the in-rubber properties of the final product to a great extent. There are several analytical methods available to determine this crosslink density like equilibrium swelling experiments, Temperature Scanning Stress Relaxation (TSSR) measurements, thiol-amine-method, H-1 NMR relaxation, stress-strain analysis according to Mooney-Rivlin or to a non-Gaussian tube model of rubber elasticity (dynamic flocculation model, DFM). SSBR/BR model compounds filled with a Silica/Silane system were produced with varying amounts of accelerator and sulfur and investigated with these different analytical methods. The evaluation shows that methods like DFM, TSSR and Mooney-Rivlin correlate very well but that the thiol-amine method is unsuitable for these silica-filled compounds.