Considering the performance of multilayer elastomer products like tires the distribution of crosslinking chemicals caused by diffusion following the assembly step during storage and vulcanization is an interesting aspect for co-vulcanization, crosslink density and influences on the adhesion systems. In this manner the diffusion behavior and the equilibrium distribution of the dithiophosphate accelerator, di-(2-ethyl)hexylphosphorylpolysulfide (SDT) between different rubber compounds used in tires was investigated by means of Fourier Transform infrared spectroscopy (FT-IR spectroscopy) and swelling. The equilibrium distribution of SDT differs as a function of the rubber matrices involved with the consequence that the concentration decreases in the direction tread undertread - steel cord mixture.