Elastomer seals are widely used as barrier seals in containers for low and intermediate level radioactive waste. In addition, they are also used in waste fuel storage and transportation as auxiliary seals. Depending on the area of use, the rubber materials have to demonstrate proper sealing performance with regard to mechanical, thermal and environmental conditions as well as irradiation during the entire operation period. A fundamental understanding of the structure property relationship can help to understand the performance of rubber seals in aged conditions. The present study focuses on the investigation of specific materials to study the structure-property and seal performance-correlation. Fluoro-elastomer (FKM), silicone rubber (VMQ) and ethylene propylene diene rubber (EPDM) were chosen as the prime candidates. Mechanical properties for these seals were achieved by careful control of base rubber formulation, i.e., by opting for the right filler and its concentration, amount of crosslinking chemicals, and with the assistance of process oils. Moreover, with the same rubber, similar mechanical properties were achieved by varying the filler concentration and crosslinking degree, which enables us to understand the structure property dependency of the seals in detail. The materials are investigated in the pristine and under aged conditions to evaluate the influence of ageing on e.g. the stress relaxation or recovery behavior. These values appear to be suitable parameters to judge the expected seal performance. Due to the electrically conducting nature of fillers used to reinforce rubbers (such as carbon blacks, carbon nanotubes (CNTs), Graphene, etc.) it is possible to obtain current information about mechanical and visco-elastic properties by monitoring the electrical conductivity or resistivity. A simple relation that bridges electrical resistance and the mechanical stress was derived and the stress values were theoretically predicted from the electrical resistance values, which showed good correlation with experimental results.