HNBR is made by conducting a selective and controlled
hydrogenated reaction with NBR. A highly saturated methylene
main chain is excellent for heat resistance and ozone resistance,
and the nitrile is oil and fuel resistant. As a result of the
hydrogenated reaction, heat and ozone resistance increase with
further hydrogen addition. Two types of polymers are commercially
usable based on the hydrogenation reaction. One is an almost
saturated type which is cross-linked only with peroxides, as the
original double bonds comprise 1%. The other is to maintain a
high rate of double bonds (5–10%) vulcanized by peroxides or
sulfur