Results of measurements of dynamic mechanical and physical properties of the ionic polymer, based on carboxylated nitrile rubber (XNBR) neutralized by zinc oxide (ZnO), reveal that ammonia works as an ionic plasticizer. Accordingly, the main chain transition is little affected but the high temperature transition due to ionic aggregates, as observed in dynamic mechanical measurements, disappeared after being exposed to ammonia for 24 h. Exposure to ammonia also caused a drop in physical properties of both unfulfilled and carbon black and silica filled XNBR-ZnO compositions.