Maleic anhydride grafted polypropylene (gPP)／expanded graphite (EG) electrically conductive nanocomposites were prepared via solution intercalation (SI) method．In contrast to melt mixing (MM) method

the relationships between preparation method

microscopic structure and conductivity of gPP／EG composites were investigated by means of measurement of electrical conductivity (σ) and OM

SEM and TEM observatians．The results show that the percolation threshold at room temperature (φc) of the nanocomposites prepared via SI method is 0.67 vol％

which is much lower than that of the composites prepared via MM method (φc=2.96 vol％)．At EG content of 3.90 vol％．the σ of the former attains 2.49×10-3 S／cm

but that of the latter is only 6.85×10-9 S／cm．The reason causing the differences mentioned above is direcdy related to the morphology and the internal microstructure of EG dispersed phase in the composites prepared via two methods．