Cross compounds in polyethylenes occur from the effect of benzoyl peroxide in the same manner as by ionizing radiation or uv light, through the recombination of polymer radicals. The compounds between the macromolecules represent the resultant of a chain process of the decomposition of benzoyl peroxide in polyethylenes. The quantitative expression of the velocity of the appearance of cross compounds depends on the analysis of the interaction velocity of the polymer radicals on the basis of the kinetic constants of the peroxide decomposition and the transfer of the primary radicai to the polymer. (tr-auth)