Dispersion mechanisms of carbon black in elastomers
Résumé
Dispersion mechanisms of carbon black pellets in uncured elastomer matrices under shear conditions were studied using a rheo-optical approach. A transparent counter-rotating plate-and-plate shear cell coupled with an optical microscope was used. Elementary mechanisms of dispersion such as rupture, erosion of isolated carbon black pellets and the role of collision on dispersion mechanisms were investigated. A criterion for rupture and an erosion law were determined. The rupture mechanism was shown to be governed by a critical shear stress which is inversely proportional to the pellet size. The erosion mechanism was found to be characterized by a constant eroded volume per strain unit. The eroded volume was shown to be independent of the initial pellet size but to depend on the applied shear stress and the strain. The effect of collision was investigated by observing the dispersion of a carbon black pellet suspended in a glass bead filled matrix. The collision of the carbon black with glass beads can induce erosion and rupture mechanisms. The erosion rate of the collision-induced dispersion was shown to depend on the frequency and kinetics energy of collision.