Fabrication of Recyclable Carboxylated Nitrile Rubber‐Based Water‐Swellable Elastomers via Ionic Cross‐linking Strategy

ABSTRACT This study presents a novel recyclable water‐swellable rubber (WSR) based on carboxylated nitrile rubber (XNBR) containing sodium polyacrylate (PAAS) and cross‐linked via an ionic network using zinc oxide (ZnO). The unique ionic crosslinks, dominated by Zn 2+ ‐carboxylate complexes, not only provide an excellent combination of mechanical strength (tensile strength > 9 MPa) and high swelling ratio (> 675% in volume) but also facilitate a closed‐loop recycling process. A facile devulcanization process involving water immersion and chloroacetic acid treatment effectively breaks the ionic clusters, allowing the recovered XNBR to be re‐vulcanized. Spectroscopic analyses (FTIR) confirmed the successful breakage and reformation of ionic cross‐links. The recycled WSR retained comparable mechanical properties and exhibited faster water absorption kinetics, attributed to a more open network structure from chain scission during recycling. Furthermore, the swelling behavior was effectively modulated by the ionic strength of the environment, demonstrating controllable performance in saline solutions. This work highlights a sustainable pathway for developing high‐performance, recyclable WSRs for sealing applications.