New Routes to Recycle Scrap Tyres

Abstract

Most means of transport need tyres as an essential component to work. Tyre composition is complex and is designed according to high technical standard requirements of adhesion, flexibility, forces and pressures, which are necessary for their functioning. However, tyres suffer from wear and have a limited lifetime due to its use. After their replacement, the unusable tyres are known as End of Life (EOL) tyres. The crosslinked chemical structure of the rubber, the high amount of stabilizers and other additives present in tyres formulations make them a non-biodegradable, nonenvironmentally friendly material. The growing environmental awareness linked to the development of new european and national regulations have instigated the research for recovering EOL tyres for other applications. A common industrial procedure prior to any form of recovery consists in grinding the tyre, in order to obtain a powder called ground tyre rubber (GTR). This powder has been proposed as a suitable reinforcement for composite materials as a way to reduce the amount of EOL tyres in added value applications. However, one of the main issues of working with GTR is its low compatibility with most of polymeric matrices used, mainly due to highly crosslinked rubber structure. Another drawback is related with the high particle size of GTR obtained by standard industrial grinding process (between 400 and 600 μm approximately) that results in brittle composite materials. Different methods have been already tested to compatibilize the polymer blends and to reduce GTR’s particle size, turning out to be too expensive procedures to provide an economically competitive material. In this chapter, several ways to blend GTR with commodity polymers were discussed. The proposed alternatives are based on the preparation of new composite materials using GTR as a reinforcement, thereby providing another way of adding value and reducing the stock of used tyres. For the development of the proposed GTR based composites, it will be necessary to improve adhesion between matrix and rubber reinforcement. In this regard, the following methods have been carried out, which was discussed in this chapter: 1) acid pre-treatment of GTR materials, 2) use of wetting additives and waxes into the mixture and 3) use of a ternary blend to prepare a thermoplastic elastomer. The effect of each proposed method on the mechanical and morphological properties of the GTR based composites was studied. Also, microstructural and chemical characterization of the composites was provided. Moreover, the materials have been optimized in order to