Experimental study on mechanical characterization of recycled rubber materials

As the present research aims to develop a low-cost rubber isolator, experimental study to observe the behavior of recycled rubbers is performed. The recycled material considered is a deactivated EPDM, produced by DERGOM Srl. In the research field, utilisations of recycled rubber materials for seismic isolation device are found in the literature. \cite{Tsang_2012,Panjamani_2015,Pitilakis_2015} investigated granulated rubbers derived from tire waste to be mixed with soil as natural seismic isolation for medium-rise buildings. In case of elastomeric isolators \cite{Calabrese_2014,Mishra_2012}, recycled rubber compounds were used to fabricate unbonded fiber reinforced elastomeric isolators (UFREIs), as a cheap isolation system. In this section, a series of experimental works are presented to observe the behavior of recycled rubbers in unaged and aged condition. However, only the unaged specimen is presented in this report, as the aging process is still on-going. This work is essential to evaluate the applicability and durability of the recycled rubber for elastomeric isolation use.  The specimens considered are RR-30 and RR-70, in which the recycled material contents are 30% and 70%, respectively.

Uniaxial tensile test

Three unaged specimens in the form of dumb-bell pieces (fig. \ref{429402}) were tested in the uniaxial tensile test device in Polimi laboratory. The result of the tensile test is presented in fig. \ref{193203}, where the specimen is stretched up to the limit of failure. As expected, the stiffest tensile curve is presented by the rubber with highest shear modulus, but it exhibits the lowest failure strain.