Sepiolite Nanofibers Decorated With Zn Single Sites: A Sustainable Filler for Mechanically Robust and Self‐Healing Ionomeric Elastomer Composites

ABSTRACT The growing demand for sustainable elastomer management has prompted the development of self‐healing cross‐linked rubbers. Recent studies showed that adding ZnO to carboxylated nitrile rubber (XNBR) creates thermo‐reversible ionic interactions. However, Zn leaching during life cycles of rubber products raises environmental concerns. Moreover, achieving both efficient repairability and high mechanical performances in elastomers remains a major challenge. To address these issues, this work introduces a novel multifunctional filler based on sepiolite nanofibers (Sep) surface decorated with Zn(II) single sites. This is designed to simultaneously provide structural reinforcement, thermally activated self‐healing properties and ensure potential reduced metal leaching from XNBR composites. Specifically, naturally occurring Sep was surface functionalized with an amino‐substituted silane (APTES) to promote the coordination of Zn(II) centers. Following surface and morphological characterization, Sep@APTES‐Zn was incorporated into XNBR to enable the formation of a thermo‐reversible ionic network mediated by Zn(II) cations and allow rubber recovery after damage. Indeed, XNBR/Sep@APTES‐Zn composites display excellent mechanical properties, remarkable self‐repairability and pronounced potential recyclability. Moreover, the structural stability of Zn(II) sites in the materials represents a valuable turning point toward the potential reduction of Zn leaching phenomena. These findings may open new avenues to design and fabricate high‐performance and sustainable rubber products with extended service lifetime.