Comparison and evaluation of different analytical methods to predict the in-rubber dispersibility of silica

The aim of the present investigation was to find a correlation between one single analytical parameter of precipitated silica and its in-rubber dispersibility. Therefore, 25 different types of silica with a variety of analytical parameters and dosage forms were investigated by means of standard analytical methods (CTAB, BET, DOA, pH and moisture content) as well as t*wo new methods, the sedimentation test and the in-situ cluster fragmentation. Moreover, all types of silica *were mixed inside a typical Green Tire formulation filled with 80 phr of silica. The macro-dispersion quality was evaluated by means of two dispersion measurement systems, the Topography where the surface roughness of a rubber sample is scanned mechanically by a probe and the Dispertester where the sample is investigated by an optical light microscope. No significant linear correlation between the standard analytical parameter and the macro-dispersion quality could be found whereas the sedimentation method and in-situ cluster fragmentation provides promising approaches. However, it was not possible to directly predict the in-rubber dispersibility of silica by means of one single analytical parameter with a very high correlation coefficient. Finally, different aspects which limit the general approach were discussed. Taking all these facts into account it becomes obvious that a linear correlation of one single analytical parameter with the dispersion quality cannot be found.