Ground tyre rubber produced via ambient, cryogenic, and waterjet milling: the influence of milling method and particle size on the properties of SBR/NR/BR compounds for agricultural tyre treads

Abstract

The increasing number of scrapped tyres constitutes a global problem. One way of recycling them is to mill the rubber waste to produce ground tyre rubber (GTR), which is utilised as a component of fresh rubber compounds for manufacturing new tyres. This paper is focused on the characterisation and application of five grades of GTR produced via three methods: ambient, cryogenic, and waterjet milling. Each GTR was separated using sieves into five size fractions. Each fraction was mixed into a fresh rubber compound based on styrene–butadiene rubber (SBR), natural rubber (NR), and butadiene rubber (BR), designed for agricultural tyre tread. The higher Mooney viscosities of GTR-containing compounds indicate different processability while the curing properties changed only moderately. Smaller GTR particles result in better mechanical properties than larger ones. The waterjet milling process seems to be the most perspective.