Abstract
The use of devulcanized tire powder as an effective reinforcement in self-healing styrene-butadiene rubber (SBR) compounds has been investigated for the first time in this work. For this purpose, the evolution of the microstructure of the rubber from end-of-life tires (ELTs) was studied during granulation, grinding and devulcanization through an exhaustive characterization work in order to relate the final microstructure with the mechanical response of the repaired systems. Different morphologies (particle size distribution and specific surface area) obtained by cryogenic and water jet grinding processes, as well as different devulcanization techniques (thermo-mechanical, microwave, and thermo-chemical), were analyzed. The results demonstrated the key influence of the morphology of the ground tire rubber (GTR) on the obtained devulcanized products (dGTR). The predictions of the Horikx curves regarding the selectivity of the applied devulcanization processes were validated, thereby; a model of the microstructure of these materials was defined. This model made it possible to relate the morphology of GTR and dGTR with their activity as reinforcement in self-healing formulations. In this sense, higher specific surface area and percentage of free surface polymeric chains resulted in better mechanical performance and more effective healing. Such a strategy enabled an overall healing efficiency of more than 80% in terms of a real mechanical recovery (tensile strength and elongation at break), when adding 30 phr of dGTR. These results open a great opportunity to find the desired balance between the mechanical properties before and after self-repair, thus providing a high technological valorization to waste tires.
Highlights
Introduction iationsTires are mandatory products for the mobility of people and goods
We report the systematic and comparative microstructural analyses of diverse ground tire rubber (GTR) and devulcanized ground tire rubber originating from end-of-life truck tires (mainly composed of natural rubber (NR)) and obtained by different methods and technologies, enabling the definition of a structural model related to the selectivity of the applied devulcanization process
The second aspect worth analyzing is the effect of the devulcanization on the healing This study the effect free polymeric on that the surface of partially capability of SBRexplored compounds
Summary
Tires are mandatory products for the mobility of people and goods. These vital elements are not capable of being recycled due to their complex structures. If one considers that the amount of natural and synthetic rubber in tires is about 60%, 6 million tons of rubber from tires are disposed each year [1,2]. In this sense, giving a second life and valorization to end-of-life tires (ELTs) has become a global priority.
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