PENETRATION OF SILICONE POLYMERS INTO SILICA AGGLOMERATES AND ITS INFLUENCE ON DISPERSION MECHANISM

The dispersion of silica agglomerates suspended in silicone fluids undergoing simple shear flows has been studied. Two different breakup mechanisms, denoted ''rupture'' and ''erosion'' have been observed. These two breakup modes produce significantly different fragment size distributions. Penetration of the suspending fluid into the silica agglomerate was found to affect the mode and the conditions necessary for dispersion of the agglomerate. Silica agglomerates totally penetrated by silicone fluids resist dispersion much better than unpenetrated agglomerates. The kinetics of matrix penetration was modeled on the basis of capillary forces driving the penetration and viscous effects resisting it. Agreement of this model with experimental observations is excellent.