Rubber compounds made of reactivated EPDM for fiber-reinforced elastomeric isolators: an experimental study

Rubber recycling technology is a popular issue in many research fields, considering the huge amount of rubber waste in the environment. This paper discusses an application of regenerated ethylene propylene diene monomer (EPDM) to produce vulcanized items such as fiber-reinforced elastomeric isolators (FREIs), which are nowadays considered efficient low-cost seismic protection devices for low rise buildings (e.g., made by masonry) in developing countries. Two types of regenerated EPDM are studies and blended with two different virgin rubbers, Vistalon 3666 and Dutral 4038. The first virgin rubber is used to produce a compound with a hardness of around 30 Shore A, while the latter exhibits 60 Shore A. The present study, which is part of a wider research project aimed at the production of low cost un-bonded seismic isolation devices, focuses exclusively on the determination of both crosslinking degree through rheometer tests and elasticity/mechanical properties of the rubber pads, before and after ageing (hardness, tensile strength, elongation-at-break, stretch-stress behavior before and after ageing). The results show that the compounds with the second reactivated EPDM (type B) exhibit the most satisfactory performance, before and after ageing. This paper discusses also the method of fabrication of FREIs, obtained by the interposition of pads made by the selected recycled rubber and dry glass fiber-reinforced polymer (GFRP) textiles. The hardness tests performed on the sliced FREI specimen indicate that the vulcanization temperature used in the production is roughly suitable to obtain the expected rubber properties.