Nitrile Rubbers (NBR, HNBR) are commonly considered the workhorse for the Industrial and automotive rubber products industry. They belong to the class of Elastomers that offer a broad range of thermal and oil resistance properties. The development of high performance, special purpose elastomers has become increasingly important in recent years and the HNBR has emerged as an important product since past few decades. All polymers are susceptible to attack by wide variety of naturally occurring and man-made agents that results in degradation of the material limiting its effective lifetime. In this work, the effect of thermal and mechanical degradation and the miscibility of different Nitrile Rubbers have been investigated using a variety of techniques. The objective is to assess whether Thermo-Mechanical degradation of these elastomers is occurring during the "conditioning" process and if so, characterize its nature and sort means to prevent it. Blending of polymeric materials is an important route to the development of new materials. Blending of unsaturated NBR and more flexible HNBR has its own scientific and economic aspects.