Highly electrically conductive polypropylene (PP) composites were prepared by melt mixing using tin-lead (Sn-Pb) alloy as conducting fillers. Two Sn-Pb alloys, Sn-Pb (20/80) and Sn-Pb (40/60), were used for comparison. The effects of Sn-Pb loading and molding temperature on electrical conductivity and mechanical properties of composites were investigated. It was found that both factors had significant effect on electrical conductivity of the final Sn-Pb/PP composite. It was interesting to observe that the molding temperature could control the formation of long-range conducting paths. The mechanism has been explored through the nonequilibrium phase behavior of Sn-Pb alloy. The influence of Sn-Pb loading on mechanical properties of Sn-Pb/PP composites was also investigated. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121:2969-2975, 2011