Anew Route Of Cross-Linking Ofcarboxylated Acrylonitrile-Butadienerubber Viazinc Oxide-Amino Acid Network Formation

Herein, we present a strategy that leads to the formation of a high-performance elastomeric material based on the carboxylated acrylonitrile-butadiene rubber (XNBR). A unique cross-linking route for XNBR has been designed, which does not involve typical cross-linking agents such as sulfur. In this study, the show cause-effect of zwitterionic compounds as the secondary cross-linking agent for ionic elastomer has been investigated. Naturally occurring lysine (Ly) and tryptophan (Trp) amino acid are the zwitterionic compounds, which have been explored here. This approach results in the formation of a cross-linked ionic elastomer that houses a dual ionic network structure formed by zinc oxide (ZnO) and amino acid. XNBR cross-linked by ZnO and different amino acid compounds exhibit superior physical properties as compared to the conventional cross-linking system. Fourier transform infrared spectroscopy, transmission electron microscope, and swelling study analyzes confirm the existence of zinc-carboxylate and zwitterionic network in XNBR after the cross-linking process. The dynamic mechanical analysis, differential scanning calorimetry, and oscillating disk rheometer analyzes show various thermal relaxations and transitions present in the dual cross-linked XNBR. The ZnO and amino acid cross-linked XNBR rubber with 2.5 phr of Ly and 5 phr of Trp show the highest tensile strength of 42.4 and 39.7 MPa, respectively, which is mostly higher than the previously reported values for ionic cross-linked elastomers.