Iron (III) cross-linked thermoplastic nitrile butadiene elastomer with temperature-adaptable self-healing property

Abstract

Fe cross-linked thermoplastic carboxylated nitrile butadiene rubber (XNBR) materials using Fe-COOH coordination as dynamic cross-links are reported. The transparent and brown Fe cross-linked XNBR (Fe/XNBR) elastomer was prepared by drying of Fe/XNBR organogels, which were fabricated by simple mixing of Fe3+ ethanol solution and XNBR dioxane solution. Tensile tests showed that only a small amount of Fe3+ ions (e.g., COOH/Fe=1/0.086, mol/mol) made the Fe/XNBR had even better tensile strength and stretchability than 2 phr sulphur vulcanized XNBR. Dynamic mechanical analysis demonstrated that the Fe-COOH interaction not only increased the moduli at higher temperatures, but also made the glass transition temperature high-temperature-shifted. In-situ infrared spectra measurements suggested that higher temperatures (e.g, 100°C) generated more trifunctional Fe-COOH cross-links and made the Fe-COOH interaction highly dynamic. The dynamic nature of the Fe-COOH interaction and generation of more trifunctional cross-links at high temperatures endowed fast self-healing and re-molding properties to the Fe/XNBR elastomers. Our result as a proof-of-concept illustrated a simple and cost-efficient way to fabricate self-healable thermoplastic elastomers using metal-ligand coordination in commercial rubbers.