The life time of elastomer components is limited by irreversible aging processes. Over the course of time mechanical-dynamic (fatigue), oxidation processes, temperature, exposition to UV light (photo oxidation) have an high negative influence on the physical and chemical properties. Functional failure of the component concerned can be the consequence. Especially in presence of high temperatures and mineral oils NBR and HNBR are used high performance polymers. The knowledge about chemical aging mechanisms, kinetics and about the weak parts in the polymer chain and in the chemical network are fundamental for life time prediction and measures in stabilizing the polymer matrix. So investigations by means of selected methods like FT-IR spectroscopy, chemiluminescence, TGA and NMR-relaxation are used to describe the mechanistic role of the ACN-groups during oxidative aging in HNBR and NBR and of the crosslinks in NBR elastomers.