The experimental data reveal that the addition of ethylene-acrylic acid copolymer (EAA) into carbon black (CB)/polypropylene (PP) composites can improve the electrical conductivity of CB/PP composites by two to six orders of magnitude at a comparatively low CB content (phi), and when (phi = 2.5 vol %, 60/40 of PP/EAA is an optimum for electrical conductivity improvement. The dynamic rheological data show that with increasing phi there are apparent rheological percolations for CB/PP composites. A modified Kerner-Nielson equation can be used to describe the correlation between electrical percolation and dynamic viscoelastic percolation. The addition of EAA into CB/PP composites leads to apparent changes in dynamic rheological behaviors. When phi = 2.5 vol %, a rheological percolation appears in CB/PP/EAA (CPE) composites with increasing EAA content. The similar rheological behaviors correspond to the similar morphological structures for CPE composites with phi = 5.0 vol %. The appearance of bumps in the van-Gurp-Palmen plots corresponds to the formation of network structure in CB/PP and CPE composites, and the more perfect the networks, the higher the amplitude of the bumps. All data indicate that the van-Gurp-Palmen plot is sensitive to the formation of filler particle networks or cocontinuous phase which spans the whole composite. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1762-1771, 2009