Tensile and Elastocaloric Properties of Natural/Devulcanized Waste Rubber Blends

The need for eco-friendly cooling materials and material recycling are two urgent challenges to address. In this paper, the role of the ground tyre rubber treatment (cryo-grinding and devulcanization) is investigated on the tensile and elastocaloric properties of Natural rubber (NR)/ ground tyre rubber (GTR). The GTR particles that are sieved (<63<mu>m) and devulcanized by microwave irradiation (1 min at 800Watts) exhibit a low network chain density (0.53 x 10(-4) mol.cm(-3)) resulting from crosslinks breakage and rubber chains scission, as supported by FTIR showing a decrease of S-S, C-S, and C-C bonds. The NR/GTR blends show a high elastocaloric effect as compared to the pristine NR, which can be ascribed to the high content of carbon black in the GTR (52 wt.%) and also the high level of devulcanization of the GTR. NR/GTR blends reach a heating of +8 degrees C and a cooling of >-6 degrees C, resulting in a material's coefficient of performance COPmat = 2.8-3 compared to 2.6 for the pristine NR. The concomitant effect of cryogrinding and microwave devulcanization is proposed as a way to improve the tensile and elastocaloric properties of natural rubber/waste rubber blends for their possible integration into elastocaloric devices for heating/cooling applications.