High‐Performance Sustainable Elastomers: New Insights Into Rubber‐Filler and Filler–Filler Interactions for Carbon Black‐Filled Natural Rubber After Recycling by Devulcanization and Revulcanization

ABSTRACT

The recycling of rubber by controlled devulcanization and revulcanization could greatly improve the sustainability of rubber products, such as tires. However, in order to use this recycled rubber, we must understand the full influence of devulcanization on not just the polymer crosslinks but also the filler network and filler‐rubber interaction. This article demonstrates that recycling by devulcanization/revulcanization strongly affects the filler‐filler agglomeration and dispersion, which had not been reported previously. By producing high‐quality devulcanized rubber, we were able to match the tensile strength and elongation at break of virgin rubber using 50 phr of recyclate, showcasing the potential for manufacturers to recycle their production waste. The rubber network structure of the recycled material was very similar to virgin, as measured by Multiple‐Quantum Nuclear Magnetic Resonance. Yet, we found that recycling reduced filler agglomerate size, confirmed using electron microscopy. Remarkably, this led to increased tear resistance for the recycled rubber. These novel recycled compounds could have important applications where high tear energy and low stiffness are desired, e.g. seals. The proposed difference in filler–filler interaction between virgin and recycled rubbers could have a major influence on the rubber recycling field, presenting new opportunities to tailor rubber product properties using devulcanized rubber.