The influence of phase transition on the filler network in the isotactic polypropylene/carbon black(emPP/CB)composite was studied.The combination of dynamic rheological and electrical measurements was used to monitor the evolution of the conductive resistivity and storage modulus of the composite during melt annealing and in situ crystallization and melting.In order to obtain a composite with a good filler dispersion state and with a strong tendency of filler aggregation

the mild blending method was used to fabricate the composite.An emPP/CB composite containing 6 wt% CB was used.The results suggest that the CB particles can aggregate and form a filler network in the composite during melt annealing

while the formed filler network could be affected by the phase transition (crystallization and melting) of the polymer matrix.In the crystallization process

the resistivity of the composite increases slightly

indicating that the growing lamellae can maneuver the filler particles and break some weak linkages in the filler network.In the melting process

the resistivity of the composite increases significantly

revealing the expansion of the polymer matrix leads to the significant breakdown of the filler network.After in situ crystallization and melting

the filler network which can be detected by the dynamic rheological experiment disappears

demonstrating that the phase transition breaks the filler network.The different developments of the storage modulus before and after phase transition show that the phase transition process cannot destroy all the aggregation structure which has formed in the previous melt annealing process.The filler network can be reconstructed quickly after in situ crystallization and melting.