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

Abstract

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.

Processing, Performance Properties, and Storage Stability of Ground Tire Rubber Modified by Dicumyl Peroxide and Ethylene-Vinyl Acetate Copolymers

“…used during GTR modification; (ii) investigation of the impact of rubber compound composition (e.g., filler, curing additives, etc.) on rubber matrix-modified GTR interfacial interactions, (iii) up-scaling of the obtained research and its industrial implementation, and (iv) searching for special applications of modified GTR allowing the further development of waste rubber upcycling technologies (e.g., materials dedicated to 3D printing [52], or self-healing [53] and thermo-responsive shape-memory materials [54]).…”

Giving a Second Opportunity to Tire Waste: An Alternative Path for the Development of Sustainable Self-Healing Styrene–Butadiene Rubber Compounds Overcoming the Magic Triangle of Tires

“…Secondly, chain mobility also decreases due to the increase in the crosslink density of the vulcanizates in the presence of GTR (see Table S2-1, Supplementary Information S2). This notorious increase in crosslink density, especially with 10 phr of GTR, could be demonstrating a more intensive vulcanization process due to the presence of TESPT [12] and of additional sulfur released during the cryo-grinding process of GTR [28]. This additional sulfur is observed on the S2p core spectrum of the as-received GTR and cryo-grounded GTR from XPS measurements (see Figure S2-2, Supplementary Information S2).…”

“…The previously reported characterization of the as-received GTR showed an average composition of 55 phr NR, 45 phr SBR/BR, and 50 phr of carbon black (CB). The full characterization of as-received GTR has been reported elsewhere [12]. As-received GTR was further pulverized under cryogenic conditions using a Cryomill (Retsch, Haan, Germany), following an optimized protocol consisting of 18 cycles with the sequence of time and frequency schematically presented in Figure S1-1 (Supplementary Information S1).…”

“…Another recent application of GTR is as a potential filler in self-healing matrices [12]. Self-healing materials are designed with the intention of extending their life span, by fully or partially repairing damage autonomously, without any external stimulus.…”

“…Overcoming this compromise is one of the actual challenges of the self-healing scientific community. Previously [12], the authors reported that the addition of 10 phr of GTR to a SBR matrix allows prevailing over such compromise, since tensile strength increased by 80 % and healing efficiency was maintained at 50 %. Meanwhile, the equivalent compound with 10 phr of a typical filler, such as carbon black, reinforced the matrix but hindered the healing ability of the compound [12].…”