Design of a new generation of sustainable SBR compounds with good trade-off between mechanical properties and self-healing ability

Self-healing polymers typically face an enforced trade-off between repairability and mechanical properties, with a high degree of self-healing being achieved mainly by materials having low mechanical strength and stiffness. This study focuses on the development of SBR compounds that can combine together self-healing properties with the use of ground tire rubber (GTR) as alternative sustainable filler. The self-healing efficiency of GTR filled SBR compounds is compared to conventional carbon black filled compounds. The influence of the vulcanization system and the addition of silane-based coupling agents are also assessed. Results show that SBR compounds vulcanized by means of a semi-efficient sulfur based system recover around 50% of their mechanical strength, being the self-healing response related to the presence of disulfide bonds. Contrary to carbon black compounds, GTR samples present similar healing efficiency to the unfilled SBR samples, improving mechanical properties in 50%. Moreover, the coupling agent enhances even more (up to 80%) the mechanical strength of the SBR-GTR compounds without adversely affecting the healing efficiency. These results can thus be seen as a starting model material for developing new sustainable applications economically and environmentally convenient with good mechanical properties as well as healing ability.