DESIGN OF ELECTRICAL CONDUCTIVE COMPOSITES - KEY ROLE OF THE MORPHOLOGY ON THE ELECTRICAL-PROPERTIES OF CARBON-BLACK FILLED POLYMER BLENDS

Effect of carbon black (CB) on the morphology of filled polyethylene ( PE)/polystyrene (PS) blends has been investigated by image analysis of optical micrographs (2-D analysis) and by the selective extraction of one phase of the binary blends (3-D analysis). The macroscopic electr ical resistivity of the filled polyblends strongly depends on the sele ctive localization of CB in one phase or at the interface and above al l on the double percolation, i.e. percolation of the polymer phases an d percolation of the CB particles. The selective localization of CB in the PE phase has remarkable effects on the polyblend phase morphology . The phase cocontinuity is indeed extended over a much larger composi tion range, and the phase morphology is stabilized toward post-thermal treatment at 200 degrees C. In the case of double percolation and sel ective localization of CB at the polyblend interface, electrical condu ctivity is observed at a CB content as low as 0.4 wt %.