Homogeneous Hydrogenation Art of Nitrile Butadiene Rubber: A Review

Hydrogenation of nitrile butadiene rubber (NBR) is an important research topic in the field of chemical modification of unsaturated polymers. This review provides an overview of the fundamental data, challenges, and recent advances in the research area of homogeneous hydrogenation of NBR. Besides NBR and its hydrogenation product HNBR, some other important elastomers such as styrene butadiene rubber (SBR), polybutadiene rubber (BR), polystyrene-b-polybutadiene-b-polystyrene (SBS block copolymer), and natural rubber (NR) were also involved for the related hydrogenation reactions and characterization. A brief comparison of hydrogenation catalysts including the heterogeneous and homogeneous catalysts was first conducted and the importance of rhodium (Rh) complex catalysts for homogeneous hydrogenation of elastomers was addressed. This article continued to discuss the reaction pathways for realization of the homogeneous hydrogenation of NBR. This was followed by an examination of the microstructures and characterization techniques of NBR and HNBR. After that the recovery/recycle of precious metal catalysts from the reaction substrate, which have been drawing much attention from industrial manufacturers, was reviewed and highlighted in this article. The applications of HNBR were then summarized. In the end, future research directions were suggested.