The physical gelation of the attractive carbon black particles in the isotactic polypropylene melt is studied. Following the method proposed by Winter and Chambon, oscillatory rheology is used to study the kinetic gelation process. The gel time, the relaxation exponent of the critical gel, the gel stiffness and the activation energy for the gelation are determined. The influences of the filler concentration and the experimental temperature on the gelation process are also investigated. The results suggest that the gelation of the filler particles in the polymer melt mainly follows second-order kinetics, and the critical gel should be formed by the rigid particles and the inter-particle polymer layers. (C) 2012 Elsevier Ltd. All rights reserved.