In this paper the different reactivities of the di- and polysulfane chains of the silanes TESPD and Si 69 in model systems and under various reaction conditions, similar to those during rubber processing, are described. Due to the different reactivities the polysulfanes of Si 69 limit the upper processing temperature while the stable TESPD tolerates excessive mixing temperatures. The reaction of the disulfane with the polymer is possible only under curing conditions and due to the different reactivities of the di- and polysulfanes the vulcanisation characteristics of silica compounds with Si 69 and TESPD are changed. Nevertheless the in-rubber performance of such compounds are similar and hence the disulfane silane has an improved processing safety.