Using an internal laboratory mixer five different bifunctional organic silanes are tested in order to check their grafting and compounding behaviour. The grafting rates, crosslinking behaviour and gel contents of the modified polymeres, detected by FTIR and hot extraction, show clear differences compared to those of the usual VTMOS in accordance with the substituents and the degree of substitution al the central silica atom. Defined changes in the structure of the grafting molecules allowed us to create agents which lead to crosslinked polymers with comparable properties, but showing better handling and processability.