Abstract: There is disclosed an insulating composition comprising a mixture of a polyolefin, such as polyethylene or polypropylene, and a partially fluorinated copolymer such as ethylene-chlorotrifluoroethylene (ECTFE) or ethylene-trifluoroethylene (ETFE) in an amount from about 3.0% to about 50% by weight polyolefin. Such mixture may be used as either a solid or foamed insulation over a metallic conductor in a plenum-type communications cable. Such an insulation has been found to have improved mechanical and electrical properties over insulations consisting of 100% ECTFE or ETFE. Specifically, the insulation exhibits improved elongation performance and lower dielectric constant and dissipation factor values. These insulated wires may be used in the transmission of electronic signals, such as voice, data or video, and possess unique properties in electrical, fire safety and cost performance.