Hydrogenated Nitrile Rubber: The Tidbits

Hydrogenated nitrile rubber (HNBR) is an interesting elastomer. As its fellow elastomers, HNBR also has a high tensile strength material, high elasticity, good abrasion resistance and low permanent set. Apart from it, the added advantage with HNBR is that it has a sound stability against thermal ageing and supports much better properties at low temperature than other oil and heat resistant elastomers. Hence, it is being heartily welcomed by the automotive industry. HNBR is a speciality engineering elastomer, and hence, its market volume is relatively small.

HNBR: The Substance
HNBR in itself is a derivative of nitrile rubber which is hydrogenated in solution with the help of metal catalyst. During composition, the nitrile groups are not effected while carbon-carbon double bonds of nitrile rubber are converted into more stable single bonds.

PROPERTIES

Mechanical Properties
HNBR has extremely good mechanical properties. These usually have high tensile strength at service temperatures of 100-140°C as well as room temperature. Moreover, HNBR vulcanisates are resistant to crack growth as conventional CR elastomers.

Thermo-Oxidative Properties
HNBR is often referred to as the '150 degree elastomer' because of its resistance to thermo-oxidative ageing. HNBR is more durable than the peroxide crosslinked vulcanisate and sulphur-crosslinked vulcanisates as it can withstand a relatively higher temperature in the engine compartment.

Cost Comparison
With so many advantages and benefits, HNBR is obviously a little more expensive than the conventional polychloroprene. The complete replacement of CR with HNBR increases the cost by around 5.7 times.

Future
More enhancements in the properties of HNBR grades will widen the scope of its usage in automotive and other industries. Car timing belts for the time being is the best example of its application, but it would soon be used for other purposes too.