The morphology of PE/CB conductive composites

The resistivity of the conductive composite varies as a function of the volume fraction of the conductive material. Considerable experimental and theoretical work has been done to examine how the volume fractions and the morphology of the components affect the electrical behavior of the composite materials. The generalized effective medium (GEM) equation gives the complete information on how the volume fraction of components may affect the medium conductivity by taking into an account the intrinsic conductivities and geometries of both components and also their arrangement and orientation in the applied electric fields. In this paper the electrical percolation phenomenon in CB/HDPE composite influenced by crosslinking under different irradiation doses and different ambient temperatures has been investigated. The experimental data regarding the dependence of conductivity on the volume fraction of CB were fitted into the GEM equation. The parameters in the GEM equation, corresponding to the dispersion characters of CB in HOPE matrix, were determined through the computer fitting. The CB particles aggregated constructing a three-dimensional conducting network along the electrical current direction. The polymer matrix,however,is statistically vertical to electrical current direction, hindering conductive particles from contacting each other. The higher the irradiation dose or the ambient temperature, the more serious the hindrance. The electrical conductivity of HOPE composites filled with high-structure CB particles is dominated by percolation mechanism based on a particle-touching model, while crosslinking or ambient temperature increasing causes a larger gap between the conductive particles and makes the conductivity more affectd by tunneling mechanism.