Films consisting of the polymer (polyvinyl alcohol (PVA)) matrix and the filler (graphitized carbon black (CB)) were prepared and examined using TMA, contact angle, and conductivity measurements. Existence of weak interaction between the molecules of PVA and the surface of CB was established. The changes occurring in the process of the thermal treatment and the chlorination of composite films were evaluated using the contact angle measurements. The results of DC conductivity measurements were approached using a model of filler cluster formation in the polymer matrix. The model of this concept is based on the percolation theory and the fractal structure of the filler network. The films exposed to environment of a certain relative humidity and the chlorinated films were examined this way. The size of the clusters, which were formed in the matrix of PVA was determined. It was established that the change of conductivity in the process of moisture adsorption runs through the aggregation of clusters. (C) 2003 Elsevier Ltd. All rights reserved.