Recycling of Waste Tyre into Silica-Rubber Compounds for Green Tyre Application

The prevention of detrimental effects to environment, owing to generation of a huge amount of rubber wastes, is a big challenge across the globe that warrants a thorough investigation of recycling and reuses waste of rubber products. In this spirit a sustainable development of a devulcanization process along with the production of value added devulcanized rubber is a task of hours. The present work describes a simultaneous devulcanization and chemical functionalisation process of waste solution styrene butadiene rubber (S-SBR). This kind of rubber is generally used as the main polymer component in silica filled tread rubber compounds for high-performance passenger car tyres. As-grown ethoxy groups on the functionalized devulcanized styrene butadiene rubber (D-SBR) are exploited for the coupling between silica and the devulcanized rubber chains. We compare the mechanical and dynamic mechanical performance of D-SBR with that of virgin SBR control composites. Covalently bonding interfaces developed from the pendent ethoxy groups of D-SBR and silanol groups on the silica surface offer a competitive and promising performance of the D-SBR based composites. We conclude that the present approach can be further utilized for the large-scale production of different rubber products with satisfied elastomeric performance.

Laboratory Evaluation of Rubberized Binder and Mix Containing a Low Content of Devulcanized Rubber Modifier

This paper evaluates the mechanical properties of rubberized asphalt binder and mix containing 5% and 10% rubber. This rubberized asphalt binder was manufactured in a field-blend process using devulcanized rubber particles, finer than 250 microns, derived from waste tires. Comparison between the rubberized binder and the base binder test results showed that the rubberized binders had higher complex moduli and lower phase angles at the grade temperature. They also had a higher percentage recovery in the multiple stress creep recovery test, and a significant creep stiffness reduction in the bending beam rheometer test. Given the low rubber content and small rubber particle size, this rubberized binder can be used in dense-graded mixes, whereas asphalt rubber binders, with larger rubber particles and higher rubber content (>15%), must be used in gap- or open-graded mixes. This rubberized dense-graded mix met the volumetric design criteria at the same binder content as the control mix prepared with the unmodified base binder. Laboratory tests on the mix included repeated load triaxial, Hamburg wheel track, flexural dynamic modulus, and beam fatigue. The rubberized mixes had slightly lower stiffnesses than the control mix, but better resistance to moisture damage, rutting, and fatigue cracking. A strong linear correlation was found between the carbonyl area index and the rheological properties of the long-term aged binder and fatigue life of the mixes. Based on these findings, these rubber-modified binders can be considered for use in dense-graded mixes to improve overall performance and make use of waste tires.