Vulcanization of carboxylated nitrile rubber (XNBR) by zinc peroxide

✍ Scribed by Ibarra, L; Alzorriz, M

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 121 KB
• Volume: 48
• Category: Article
• ISSN: 0959-8103
• DOI: 10.1002/(sici)1097-0126(199907)48:7<580::aid-pi186>3.0.co;2-4

✦ Synopsis

The vulcanization of carboxylated nitrile rubber (XNBR) with zinc peroxide, which produces ionic crosslinks, has been studied in relation to vulcanization time. Vulcanized compounds present two transitions, corresponding to the glass transition of the polymer at low temperatures and the ionic transition resulting from the formation of ionic aggregates. Both transitions are displaced to higher temperatures with increasing crosslink density. The ionic associations which give rise to high values of mechanical properties disappear on exposure of the vulcanized compounds to saturated ammonia vapour. This treatment produces a decreased crosslink density resulting in the disappearance of the ionic transition. When the action of ammonia is terminated by immersion in solvent followed by drying, the original crosslink density is recovered and the ionic transition reappears, although at higher temperatures. However, with increasing crosslink density, the difference between the temperatures at which both transitions take place diminishes. All these factors can be interpreted as re¯ecting the generation of a new and more compatible arrangement of the newly-appearing ionic clusters.