Analytical method development to predict the in-rubber dispersibility of silica

The aim of this thesis was to predict the in-rubber dispersibility of silica by means of one sin-gle analytical parameter. Therefore, standard analytical parameters of silica as well as pa-rameters obtained by three newly developed methods were investigated and correlated to the in-rubber macro-dispersion quality. To evaluate the dispersibility of different types of silica, it was essential to use an identical formulation and an identical mixing process. A variety of sili-ca with different analytical parameters were investigated and their effect on in-rubber proper-ties, especially the macro-dispersion quality, within different compounds was evaluated.

The first approach was the investigation of the void volume structure measurement. This new analytical system was used to determine the initial structure of silica which is known from previous investigations to influence the dispersion process.

A second attempt was to transfer the dispersion process into the laboratory. For this purpose, a solution of silica and demineralized water was treated with ultrasound in order to simulate the dispersion process of silica in rubber. After this preparation, the particle size distribution of the silica in the suspension was measured by the use of a sedimentation analysis.

A third approach to predict the in-rubber dispersibility of silica is the use of the in-situ cluster fragmentation. During the measurement a silica sample circulates in a fluid (e.g. water) loop. The suspension passes an ultrasonic device and thereby bigger clusters get fractured into smaller ones. The particle size and distribution are continuously measured over the meas-urement time via laser diffraction. In this way the decrease of clusters can be recorded over a certain time.

It turned out that many different factors influence this direct correlation which makes it more difficult to predict the dispersibility sufficiently. By using a data analyzing model, a combina-tion of different analytical parameters could be found which provides an improved indication compared to the single linear correlation. Moreover, by means of the newly developed meth-ods it was possible to get a better insight into the dispersibility of silica and to get a deeper un-derstanding of the morphology of silica.