Carbon black (CB) filled polypropylene (PP) nanocomposites were prepared by using a mild blending method in the present study.In this compounding process

the CB particles were first dispersed at the nanoscale in aqueous suspension by ultrasonic irradiation.Subsequently

the CB suspension was blended with melting PP using a twin-screw extruder with low shear stress screw configuration

followed by removing the vapor from the vent by vacuum

and the CB particles were located in the PP matrix almost as they were in suspension.The SEM results showed that the CB particles were dispersed at nanometer level in the nanocomposites and distributed homogeneously in PP matrix.The common CB/PP composites had a percolation threshold of about 7.66 vol%

whereas the CB/PP nanocomposites prepared by mild blending method exhibited a very low percolation threshold

i.e.

2.49 vol%.The percolation critical resistivity-exponent t of this nanocomposite was estimated

i.e.

ca. 5.4

which indicated that the system did not obey the prediction of the universal percolation theory.These results were likely attributed to the homogeneous distribution of CB particles

most of which did not contact closely with each other.A conductive model

based on the tunneling conduction theory

was established to simulate and explain these phenomena.The simulation result showed that the relationship between average volume conductivity of the CB/PP nanocomposite and variable （p-pc） deviated from linearity

with the maximum simulated t value as 6.3 Furthermore

it also shared the similar trend with experiment results

indicating that the electrical propertyies of CB/PP nanocomposites prepared by mild blending method were controlled by the percolation tunneling mechanism.