In situ study of the dynamics of erosion of carbon black agglomerates

With the help of a counter‐rotating transparent rheometer equipped with an optical microscope, the erosion of single, commercial carbon black agglomerates suspended in a polyisobutylene fluid was accurately recorded in situ . We observed that clouds of very small aggregates were leaving the agglomerate at 45 and 225° in the shear gradient–flow direction plane, where the stress is maximum. The distribution of the arrached aggregates is more efficient when the carbon black agglomerate is more asymmetric. A spherical agglomerate of critical radius R 0 will reach a radius R t at time t following R   3 0− R   3 t= at , a being a constant. This implies that the rate at which the number of aggregates is leaving the agglomerate is a constant, independent of the size of the agglomerate. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1627–1629, 2001