a composition stabilized against oxidative degradation comprising : a polyolefin , carbon black homogeneously incorporated in said polyolefin , a stabilizing amount of a n - phenyl - n &# 39 ;-- p - phenylenediamine first stabilizer component incorporated into said polyolefin and a second stabilizer component of at least one amine antioxidant selected from the group consisting of a para - substituted aralkyl - substituted diphenylamine ; a para - phenylenediamine and a polymerized dihydroquinoline incorporated into said polyolefin .