The present work focuses on the analysis of two composites: a pure amorphous Polystyrene and a rubber modified Polystyrene (High Impact Polystyrene), both filled with Carbon Nanotubes (CNT) for generating Conducive Polymer Composites (CPC). Recently, CPC has been obtained with very low filler content following a volume segregation strategy which maintains the filler in one continuous phase. This phenomenon enhances the contacts between fillers and consequently gives birth to conducive composites with ultra-low filler concentration. In this work the two composites are analyzed using a specific set-up that gives the possibility to monitor both electrical conductivity evolution and the elongational stress in the melt state. This set-up allows determining the maximal deformation that nanocomposites can undergo before becoming insulating. In addition, the dynamic of the network evolution that is, its destruction and structuring has been analyzed. When the destruction is predominant, the two composites behave the same. However, we have observed a slight disparity when there is a possible competition between destruction and structuring during extensional deformation. This difference has been accounted to the presence of the nodules that might locally prevent the structuring mechanism during extensional deformation.