A mixture of high-density polyethylene and its low-molecular-weight analogue heptadecane was studied. The mixture behaved as a compound, that is, differently from polyethylene. Heptadecane reduced the crystallinity of polyethylene, and it intricately changed the concentration of centers sorbing phenyl-beta-naphthylamine, the antioxidant, and simultaneously changed the equilibrium constant of sorption. Heptadecane also prolonged the duration of the antioxidant action in polyethylene. (C) 2003 Wiley Periodicals, Inc.