ReTyre

Rubbers are generally chemically cross-linked (vulcanised) to make them suitable for use in tyres. This cross-linking ensures durability, prevents the rubber from melting and influences its mechanical properties; however, it also prevents the material from being remelted and reshaped for recycling, as for thermoplastics. The ReTyre project aims to develop a continuous, scalable process to reverse the cross-linking so that waste tyre rubber can be reshaped and subsequently vulcanised again. To date, the disposal of end-of-life tyres primarily relies on thermal recovery or open-loop recycling, for example for use in asphalt or sports grounds. Material recycling has not yet been achieved, even though end-of-life tyres are generated in very large quantities.

This is not only because of the need to break the crosslinks (whilst avoiding damage to the polymer chains) but also due to the complexity of the material: in addition to spring steel and textile components, tyres contain various types of highly filled rubbers. While steel and textiles can be separated from the rubber, separating and sorting of the different rubbers would be extremely labour-intensive and therefore economically unviable. A continuous and scalable reactive extrusion process is intended to de-vulcanise the shredded and unsorted rubber (excluding steel and textile components). By mixing it with virgin material and subsequent re-vulcanisation without a loss of mechanical properties, tyre-to-tyre recycling will be advanced. The TCKT is working on this ambitious project in collaboration with KIAS Recycling GmbH, the only tyre recycling plant in Austria.