Given their exceptional performance qualities, the demand for Hydrogenated nitrile (HNBR) elastomers is increasingly globally, says Dr Mosongo Moukwa

 

Hydrogenated nitrile elastomers (HNBR) represent specialty elastomers with the smallest consumption volume yet, but the fastest growing specialty elastomers. According to a report by Research and Market, HNBR elastomers are on the rise, growing at a double-digit annual rate. Given their exceptional performance qualities, HNBR elastomers are used in the automotive industry (timing belts, hosing, seals and gaskets), in the oil industry (stator pumps, packing seals and blowout preventers), as well as in other industries for applications such as cable coverings or laminated rollers. They are sometimes recommended in place of fluoroelastomers (FKM) because of their oil resistance and thermal ageing and cost advantage. 

 

Hydrogenated nitrile elastomers are produced by the catalytic hydrogenation of acrylonitrile butadiene copolymer elastomers (NBR). The hydrogenating process saturates the polymeric chain with accompanying improvements to the ozone, heat and aging resistance of the elastomer and overall mechanical properties. HNBR have good stability towards thermal ageing, but also better properties at low temperatures compared to other heat- and oil-resistant elastomers. They are more suitable for withstanding the relatively high temperatures in the auto engine compartment, which can reach 135-140°C in the timing belt area. 

 

Compared to traditional nitrile elastomers, they are much more resistant to oxidation and sulfur attack at higher temperatures, filling the gap left by traditional nitrile elastomers (NBR) and fluoroelastomers when high temperature conditions require high tensile strength while maintaining excellent resistance to oils and fuels. 

Two companies manufacture commercial HNBR polymers: Lanxess (Germany) under the trademark Therban and Zeon Chemicals (USA) under the trademark Zetpol. Zeon Chemicals Ltd is a wholly owned subsidiary of Zeon Corp of Tokyo, Japan. These suppliers offer a wide range of grades for a range of applications. 

 

 

Global capacity

 

Strong demands in China have contributed to the high growth rate of hydrogenated nitrile elastomers, although their consumption is concentrated in USA, Europe and Japan. In Asia, Zeon Corporation and Lanxess hold respectively 29 percent of capacity (5,300 MTPA) and 4 percent (500 MTPA) respectively. In Europe, Laxness has a dominant presence with 5,000 MTPA capacity (31 percent). In 2012, Lanxess expanded its HNBR capacity by 40 percent at its facilities in Germany and in the US in order to meet the double-digit demand growth. Zeon Chemicals also expanded its HNBR capacity by 25 percent at its US plant. PetroChina Lanzhou Research Center of Chemical Industry had constructed a 30 tonne per annum NBR pilot unit that can produce HNBR varieties. 

 

Technology advances

 

Advances in technology have led to a large variety of specialty grades of HNBR currently available on the market, meeting specific customer demands. Currently, automotive manufacturers require good low-temperature performance to meet the needs of a cold start at -40°C, and to meet extended use at 125-150° C for parts exposed to a heat source. New compounding techniques, comprising of some combination of the high phosphorus mineral fillers, addition of magnesium oxide, and an optimised heat stabiliser system, have been developed. Compounders have also added plasticisers that do not leach out when parts are exposed to higher temperatures for several 

days, preventing a loss of low-temperature functionality.

 

Finally, new low viscosity polymers that can be processed as easily as traditional nitrile polymers, while retaining the advantageous properties of HNBR, have been developed. Up until now, ultra low viscosity HNBR polymers were impossible to manufacture because of limitations in the available viscosity for NBR feedstocks. 

Advances in carboxylate technology have allowed the development of carboxylated HNBR (HXNBR), which offers the advantages of carboxylated NBR but with the improvements in heat resistance and abrasion afforded 

by the hydrogenation of the polymer backbone. 

 

 

Dr Mosongo Moukwa is an Independent

Consultant based in Chapel Hill, USA. He was Director of Technology at PolyOne, USA and a former Vice President of Technology at Asian Paints, Ltd., Mumbai, India. He is a member of the American Chemical Society and Product Development Management Association. 

Email: mosongo@mosongomoukwa.com