FRACTAL STRUCTURE STUDY OF CARBON-BLACKS USED AS CONDUCTING POLYMER FILLERS

We characterize the fractal dimension of various carbon blacks by transmission electron microscope image analysis of aggregates and small-angle neutron scattering of filled polymer samples. The results obtained by these two distinct techniques are in very good agreement and are found close to the prediction of the cluster-cluster aggregation model. Furthermore, we determine the volume fraction of carbon black at the insulating-conducting transition of composite materials elaborated with the same blacks, but we do not find a correlation of this threshold with the fractal dimension of the aggregates. This questions the relevance of the fractal concept in the prediction of the physical properties of composites.