Influence of crosslinker and water on mechanical properties of carboxylated nitrile butadiene rubber (XNBR)

Carboxylated nitrile butadiene rubber (XNBR) belongs to the group of ionomers as it comprises ionizable carboxylic acid groups. Its molecular structure enables to pursue several crosslinking routes, resulting in the formation of either covalent or ionic bonds. This study focuses on the effect of ionic and covalent crosslinking on the structure and mechanical properties of XNBR. Furthermore, the effect of water on mechanical properties (tensile tests, stress-rupture tests) is assessed as a function of exposure time in water for swollen and de-swollen samples. The network density shows a good correlation with the swelling degree and mechanical behavior obtained from tensile tests. The results reveal that the introduction of covalent bonds restricts ionic rearrangement processes and is crucial for static durability in water. [Display omitted] •Network structure controls material behavior and water resistance of XNBR.•Good correlation of equilibrium swelling and low field NMR results.•Exposure to water promotes rearrangement of ionic multiplets in cured XNBR.•Covalent bonds improve static durability of XNBR exposed to water.•Higher stress recovery at high ionic crosslinker content after removal of water.