Abstract: An insulated conductor (20) for use in a communication cable which includes a filling material (30) includes a copper conductor (25) and a composite insulation system (27) comprising two concentric layers of insulation. An inner foam layer (28) of the insulation comprises a cellular plastic material (28) which includes a stabilizer system. An outer layer (29) of the insulation is referred to as a skin and comprises a stabilized solid plastic material. The stabilizer system in each of the cellular and solid layers includes a bifunctional portion that functions as an antioxidant and as a metal deactivator and that has a relatively high resistance to extraction. The level of the bifunctional portion of the stabilizer in the cellular material is substantially greater than that in the skin inasmuch as it has been found that the level of the stabilizer cellular layer contiguous to the copper wire determines the oxidation performance level of the composite insulation.