In-situ study of the fragmentation process of agglomerated filler in a rubber matrix.
Résumé
We developed a transparent counter-rotating shear cell coupled with an optical microscope. The counter-rotating geometry allows us to stabilize the particle in suspension in a liquid matrix submitted to a shear flow relatively to the laboratory framework. It is then possible to observe the behaviour of this particle under the effect of hydrodynamics stresses. If the particle is an agglomerated object and if the hydrodynamics stresses are larger than its cohesion strength, fragmentation takes place. We thus applied this technique to study the fragmentation process of agglomerated fillers such as carbon black and silica suspended in a styrene-butadiene rubber. Different fragmentation processes were observed and characterized. Quantities such as the minimum shear stress to be applied to reduce the size of the agglomerated filler are determined.
The comparison of different grades of carbon black and precipitated micropearl silica allows us to better understand the mechanism of fragmentation of such agglomerated fillers. Conditions for fragmentation could be related to the agglomerate internal organisation. The experimental procedure, the validity of the measured data and the models used to interpret the data will be discussed.