The results of relaxation test are presented in fig. \ref{479291}, showing three tests on each specimen. All specimens are in unaged condition. However, within four days at room temperature, the specimens show a remarkable difference in relaxation behavior. Finally, fig. \ref{109458} shows an accurate fitting of Prony series model on both specimens. Having hyperelastic and viscous properties of the specimens, we are able to simulate the rubber behavior in 3D FE analyses.