Effect of melting and crystallization on the conductive network in conductive polymer composites

Investigation on the effect of melting and crystallization of polypropylene (PP) on the conductive network of multi-wall carbon nanotubes (MWNTs) and carbon black (CB) in MWNT/PP and CB/PP composites is performed. The conductive networks formed by fillers with different aspect ratios (MWNTs and CB) are compared during melting and cooling experiments. The network is found to be deformed during melting and re-constructed again due to the re-agglomeration of fillers during isothermal annealing of the melt. Both deformation and re-construction of the network result in a substantial increase/decrease of the thermal resistivity of MWNT/PP and CB/PP composites. For the modelling of the dynamic network reformation three different approaches are tested: classic percolation theory, general effective medium theory (GEM) and Fournier equation.