Butadiene-acrylonitrile hydrogenated copolymer (HNBR) is widely known for preserving properties after long-term heat exposure and excellent resistance to fluids used in the automotive and industries in general. This type of rubber is also extremely resistant to traction, abrasion -even at high temperatures- and ozone.
It is possible to partially or completely hydrogenate the nitrilic rubber molecular chain, which allows to obtain polymers with high temperature and oil resistance.
Disadvantages include high costs and limited resistance to aromatic oils and polar organic solvents, poor electrical properties and low flame resistance.
It is a synthetic polymer, obtained from hydrocarbon rubber chains saturated with nitrile with hydrogen. This special process of hydrogenation reduces many double bonds in the NBR polymer chains, therefore, HNBR presents a higher resistance to heat, ozone and chemical substances, in addition to superior mechanical characteristics compared to the standard of nitrile.
Regarding vulcanization, completely hydrogenated product grades are cross-linked with peroxides, while partially hydrogenated grades, with a level of unsaturation from 3 to 5%, can be cross-linked with sulphur to improve flexibility properties in dynamic systems, but this will reduce compound heat resistance and will result in a worse compression set.
Hydrogenated nitrile (HNBR) is used in many fields, however, the largest consumption of this type of rubber is in the automotive market segment. It is mainly used to make joints, pipes and straps for both dynamic and static application. It is also used for the production of O-rings and is also present in the oil drilling market segment as a sealant.