STRUCTURE AND PROPERTIES OF REINFORCING FRACTAL FILLER NETWORKS IN ELASTOMERS

The effect of filler networking on mechanical and electrical propertie s of elastomers is discussed on the basis of percolation theory and a recently developed kinetical cluster-cluster aggregation (CCA) model, respectively. In percolation theory pure geometrical arguments are con sidered and the physical properties of the filler network are related to the infinite cluster that is formed at percolation threshold. In th e CCA-model the particles are allowed to fluctuate around their mean p osition on length scales that are comparable to the polymer fluctuatio n length. Upon contact of neighboring particles or clusters they stick together and form larger clusters. At sufficiently large filler conce ntrations (above the gel point of the filler network), a fractal fille r network results that corresponds to a space-filling configuration of CCA-clusters. Structure and properties of the filler network in this model are compared to the fractal characteristics of percolation netwo rks. In particular, the influence of anomalous diffusion of charge car riers on the scaling behavior of the conductivity is demonstrated for both types of fractal networks. For the elastic modulus an universal p ower law behavior results that is independent of the size of the fille r particles and the applied rubber in both cases.