Al2O3 Decorated with Zn Single Sites: A Multifunctional Filler for Upgrading the Properties of XNBR Composites

A multifunctional alumina-based filler, Al2O3@APTES-Zn, has been synthesized by functionalizing Al2O3 nanoparticles with aminopropyl triethoxysilane (APTES) and subsequently anchoring Zn2+ centers. This multifunctional nanofiller acts simultaneously as a reinforcing agent, cross-linking promoter, and thermal conductivity enhancer in carboxylated nitrile rubber (XNBR) composites. The anchored Zn(II) sites also provide ionic interactions with XNBR terminations, enabling dynamic reversible bonds for self-healing properties. The comprehensive characterization of XNBR/Al2O3@APTES-Zn composites unveils enhanced cross-linking, improved tensile strength and strain at break (up to 17 MPa and 1416% at 24 phr filler), increased thermal conductivity (+11.4% compared to neat Al2O3 at the same loading), and superior self-repairing efficiency (up to 120%). These results demonstrate that the tailored surface and interfacial properties of Al2O3@APTES-Zn represent a promising benchmark for resilient and sustainable composites in applications, such as hoses, seals, gaskets, and automotive components.