Nitrile-butadiene rubber degradation products

Problem 5-18 (Level 3) Parent et al. have studied the selective hydrogenation of C=C bonds in nitrUe-butadiene rubber (NBR) to produce hydrogenated nitrile-butadiene rubber (HNBR), which has superior resistance to thermal and chemical degradation. To obtain the desired product, the rate of hydrogenation of C=C bonds must be much higher than the rate at which the nitrile group (- C=N) is hydrogenated. 

The hydrogenated products are nitrile rubber, with good heat resistance, and styrene-butadiene-styrene copolymer, with high tensile strength, better permeability and degradation resistance. 

The mechanical degradation and production of macroradicals can also be performed by mastication of polymers brought into a rubbery state by admixture with monomer several monomer-polymer systems were examined (10, 11). This technique was for instance studied for the cold mastication of natural rubber or butadiene copolymers in the presence of a vinyl monomer (13, 31, 52). The polymerization of methyl methacrylate or styrene during the mastication of natural rubber has yielded copolymers which remain soluble up to complete polymerization vinyl acetate, which could not produce graft copolymers by the chain transfer technique, failed also in this mastication procedure. Block and graft copolymers were also prepared by cross-addition of the macroradicals generated by the cold milling and mastication of mixtures of various elastomers and polymers, such as natural rubber/polymethyl methacrylate (74), natural rubber/butadiene-styrene rubbers (76) and even phenol-formaldehyde resin/nitrile rubber (125). 

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