The reason to develop NBR is to replace Natural rubber and enhance physical and chemical properties. The history of NBR can be traced back between 1914 and 1922, when the price of Natural rubber fluctuated from 11.5 cents/lb to as high as $1.02/lb. The supply from Asia faced shortage in 1925, and the price of natural rubber reached $1.12/lb.
In response to the severe shortage, German and American companies started to research on synthetic rubber as a potential alternative.
Finally, the first successful synthetic rubber, Buna, was patented by Germany's I. G. Farben Industrie in 1926. You may not recognize this company, but you have probably heard of its successors, such as BASF and Bayer.
Meanwhile in the US, DuPont's Arnold Collins has successfully developed polychloroprene rubber in 1929, which is now known as Neoprene. The new material was commercialized in 1933.
Several American rubber companies also began to develop copolymer rubbers of their own, such as Goodyear's Chemigum, or BF Goodrich's Ameripol. Standard Oil (which is now ExxonMobil), at the meantime, developed butyl rubber in 1937.
The most notable discovery during the 1930s was IG Farben's team polymerizing a synthetic rubber called Buna-S from butadiene and styrene in an aqueous emulsion. Currently known as styrene butadiene rubber (SBR), Buna-S had been produced in large quantities in Germany by 1935.
IG Farben scientists also developed nitrile rubber Buna-N in 1931, and began its mass production in 1935, laying the cornerstone of NBR. During the World War II, Nazi Germany prevented the export of NBR to the UK and the United States. Hence, Standard Oil and other companies license by IG Farben started their own NBR production. After World War II, IG Farben defuncted and was separated into multiple companies. The Buna brand was licensed to Bayer. And eventually in 2005, Bayer strategically spun off Nitrile rubber to LANXESS.
In 2016, LANXESS and Saud Aramco formed a joint venture company, ARLANXEO, and continued to produce Nitrile rubber under the trademark of Perbunan. Besides those companies we just mentioned, there are many other major Nitrile producers, such as Zeon Chemical or JSR Corp.
Firstly, at the polymer synthesis level:
The ACN content is typically described as "the Acrylonitrile content" or "ACN content" of the polymer chain. The ACN content ranges from 18% to 50%. The higher the ACN content, the better the fuels and oil resistance level is. The most common and balanced grade of NBR content is 36% of ACN
Secondly, the curing system. Standard NBR is sulfur cured due to the butadiene unsaturated structure. Small amount of sulfur with aggressive accelerators is the most cost-effective way to cure NBR. Organic peroxide curing system can improve compression set at 150°C, especially when being used with co-Agents, such as TAIC (triallyl isocyanurate) or TAC (triallyl cyanurate).
The third factor is the filler and additive added to the compound. Like in the case of other rubbers, filler and other additives can significantly enhance NBR's chemical and physical performance.
We will elaborate more about compounding ingredients in other episodes. Now just note that common ingredients include:
5. Process oils
By adding these ingredients into the formulation process, we can create different compounds, which are used in different applications. The oil, fuel, and heat resistance feature of NBR has made this elastomer very important to the automotive non-tire and industrial rubber businesses.
NBR is considered to be the major oil, fuel, and heat resistant elastomer in the world. It is commonly used in automotive industry, ranging from hydraulic hoses, fuel and oil supply hoses, seals, rollers, drive belts, to fabric linings and gaskets. In addition, the increasing prevalence of light weight vehicles boosts the automotive industry's demand for Nitrile rubber.
NBR-based seals & O-rings, hoses, and other oil & gas hardware goods are significantly consumed in oil & gas applications, owing to their high oil & fuel resistance.
And our final note on NBR is, besides auto and energy applications, glove and medical devices also play an important role on nitrile consumption.