Structure and electrical properties of grafted polypropylene/graphite nanocomposites prepared by solution intercalation

A novel process was developed to prepare electrically conducting maleic anhydride grafted polypropylene (gPP)/expanded graphite (EG) nanocomposites by solution intercalation. The conducting percolation threshold at room temperature (Phi(c)) of the nanocomposites was 0.67 vol %, much lower than that of the conventional conducting composites prepared by melt mixing (Phi(c)=2.96 vol %). When the EG content was 3.90 vol %, the electrical conductivity (sigma) of the former reached 2.49x10(-3) S/cm, whereas the sigma of the latter was only 6.85x10(-9) S/cm. The TEM, SEM, and optical microscopy observations confirmed that the significant decrease of Phi(c) and the striking increase of sigma might be attributable to the formation of an EG/gPP conducting multiple network in the nanocomposites, involving the network composed of particles with a large surface-to-volume ratio and several hundred micrometers in size, and the networks composed of the boards or sheets of graphite with high width-to-thickness ratio and particles of fine microscale or nanoscale sizes. (C) 2003 Wiley Periodicals, Inc.