High-density polyethylene (HDPE)/polypropylene (PP) composites with graphenes were prepared by melt-compounding method. Graphene sheets were prepared through thermally reduced graphene oxide (TRG) and surfactant exfoliated graphene (SEG), respectively. Structural characterization showed that the TRG sheets exhibited a few-layers composition with more defects compared to the SEG sheets. Morphological observations of the composites demonstrated that the graphene was preferentially dispersed in the HDPE phase and the addition of graphene (TRG and SEG) influenced the phase structure of the HDPE/PP composites. The distribution of the TRG sheets in the HDPE phase was better than the SEG sheets, and the obtained HDPE/PP composites exhibited a low electrical percolation threshold with the highly dispersed graphene. The TRG/HDPE/PP composite showed a low electrical percolation threshold of 3 wt% (1.25 vol%). For the SEG/HDPE/PP system, the percolation threshold was 7 wt% (2.98 vol%). Differences in the behavior of the two graphene components (TRG and SEG) in the HDPE/PP composites influenced the formation of percolation networks and electrical properties. (C) 2015 Society of Plastics Engineers