Vulcanization of regenerated rubber pads for seismic base isolation of low rise masonry buildings

The vulcanization process of a low cost parallelepiped seismic rubber isolation device is studied from a numerical standpoint. The seismic isolator is constituted by few rubber pads made by regenerated rubbed and EPDM and -instead of steel laminas- GFRP sheets are utilized to reduce further the production cost. Such cheap device, assuming also its installation without head and foot connecting steel plates, is particularly suited for the isolation of low rise masonry buildings in developing countries. A refined FE discretization is utilized to predict the temperature-time histories that each point of the device exhibits during a standard vulcanization in an industrial oven. The knowledge of the temperature profiles is mandatory to predict the local final vulcanization degree, once that a suitable vulcanization model is at disposal. From simulations results, it is found how the utilization of steel laminas -thanks to their high thermal conductivity- allows a much faster and homogeneous vulcanization inside the bulk, whereas the introduction of pultruded GFRP sheets is equivalent to the vulcanization of a single thick rubber pad. As a consequence, in this latter case there is the need to extend curing to long vulcanization times, always associated to over-vulcanization of the skin and under-vulcanization of the core.