Preparation of hybrids consisting of expanded graphite and carbon nanotubes as conductive fillers of polybutylene terephthalate

Expanded graphite (EG) was loaded with iron by impregnating with ammonium carbonate and ferric nitrate solution. Carbon nanotubes (CNTs) were grown on the EG by iron-catalyzed chemical vapor deposition, using acetylene as a carbon source to form hybrids that were used as a conductive filler to produce conducting polybutylene terephthalate (PBT) composites by an extrusion method. It is found that the CNTs are not entangled and are easy to disperse. The CNT average diameters are 40, 20 and 40 nm, and their lengths are 2, 3.7 and 2.6 mu m for iron loadings of 1.13, 0.75 and 0.57 mass%, respectively. The thickness of the EG is reduced to 10-30 nm as a result of CNT insertion into the graphene layers of the EG. The content of CNTs in the hybrids increases from 50 to 85 mass% with the increasing iron content. The conductive PBT modified by the hybrids (5 mass%) derived from EG loaded with 0.75 mass% iron has a surface resistance of 1. 55 x 104 Omega/cm(2), significantly lower than that (1.55 x 1010 Omega/cm(2)) of the PBT modified by CNTs with the same amount of filler added.