Microwave activation of ground tyre rubber and its application in off-road tyre tread formulation

Abstract

Finding a way to increase the amount of recycled waste tyres is a current global challenge. Among others, the production of ground tyre rubber (GTR) and its application in a new rubber compound looks as a perspective way. However, the compatibility of GTR and rubber matrix is limited, leading to insufficient properties of the new material. To improve them, it is suitable to activate the GTR prior to mixing. In this paper, GTR obtained by water jet process was activated with microwave irradiation (i) in a household oven at 400 W and 800 W for 1 and 3 min, and (ii) in an industrial device at 500 W, 1000 W, 1500 W and 1750 W for 1, 3 and 5 min. A total of 7% (w/w) of the irradiated GTR was incorporated into a carbon black-filled rubber compound based on styrene-butadiene rubber (SBR), natural rubber (NR) and butadiene rubber (BR), with a formulation for off-road tyre treads. Most compounds containing microwave-treated GTR showed comparable or better properties than the reference with untreated GTR (tensile strength, 14.9 MPa; elongation at break, 437%; modulus at 300% elongation, 8.97 MPa; hardness, 65.6 Shore A). The industrial microwave device offered better results and the possibility of use of higher variation in conditions than the home microwave oven.