HNBR is a highly saturated special elastomer obtained by hydrogenation of nitrile rubber (NBR). Compared with NBR, HNBR has little or no carbon carbon double bonds in its molecular structure. While maintaining NBR’s oil resistance and wear resistance, it also has more excellent heat resistance, oxidation resistance, ozone resistance, radiation resistance, chemical resistance and other properties. It is a special rubber with excellent comprehensive performance.
At the end of 2021, the Ministry of Industry and Information Technology of China released the “Guiding Catalogue for the First Batch Application of Key New Materials (2021 Edition)”, which will be implemented from January 1, 2022. Among them, under the category of advanced chemical materials, hydrogenated nitrile rubber (HNBR) products are added to special rubber and other polymer materials.
HNBR Sealing Belt
Why is HNBR highly anticipated?
Let’s take a look at its advantages over traditional rubber.
1.HNBR compared with NBR(nitrile rubber)
When the actual application of NBR exceeds 120 ℃, the double bonds on the main chain, namely the butadiene chain, are attacked by oxygen, causing bond breakage, causing NBR to prematurely lose its high elasticity and application function. Compared to NBR, HNBR has better heat resistance, higher tensile strength, and can withstand low temperatures up to -50 ℃. For example, in the application of automotive component products, conventional NBR can be used at a temperature of 100 ℃, while specially formulated NBR can be used at 150 ℃.
However, in acidic gasoline and high temperature environments of 150 ℃ for a long time, its ozone and radiation resistance are poor, and it can no longer meet the sealing requirements of vehicles for engines. However, HNBR can reach a conventional use temperature of 150 ℃, and its tensile strength and aging resistance are even better, Therefore, the gearbox seals, shock absorber oil seals, and power steering oil seals produced using NBR in the past have gradually switched to HNBR.
2.HNBR compared with FKM( fluororubber)
Due to the need for environmental protection, automotive fuel often contains various additives, such as methanol, ethanol, methyl tert butyl ether, amine corrosion inhibitors, anti wear agents, etc., which puts higher requirements on rubber components in contact with fuel. Both HNBR and fluororubber have excellent fuel oil resistance, corrosion resistance, and low medium permeability.
Compared with fluororubber, HNBR has higher tensile strength, better resistance to chemical corrosive media, and stronger cold resistance. For example, in the application of seals and other products in the field of automobile manufacturing, it is required that rubber products maintain normal function within the temperature range of -40 ℃ to 150 ℃, while fluororubber can work for a long time at 200~250 ℃.
However, fluororubber deteriorates its low temperature resistance as the fluorine content increases. HNBR’s low temperature resistance can reach -50 ℃, and its high temperature resistance is 150 ℃, which can meet the above requirements. When choosing HNBR brand with an acrylonitrile content of about 43%, It can achieve a good balance between fuel oil resistance and low temperature resistance, and its overall performance is better than that of fluororubber.
3.HNBR compared with CR(Neoprene)
Neoprene has the same good oil resistance and higher physical and mechanical properties as HNBR, but when it is used to manufacture rubber parts Timing belt under dynamic stress, HNBR has obvious advantages, especially when it is used at high temperature and for a long time. Under dynamic stress, HNBR still has high physical and mechanical properties after long-term high-temperature aging, with small dynamic permanent deformation, small changes in elongation and hardness. However, under the same conditions, chloroprene rubber is often damaged and loses its value in use.
For example, in the application of automotive Timing belt products, neoprene with good comprehensive performance was originally used for automotive Timing belt, but with the continuous development of the automotive industry, the speed and power of the automotive engine are constantly increasing, and the requirements for the heat resistance of Timing belt products exceed 120 ℃. Under this condition, neoprene Timing belt has been difficult to meet the requirements. HNBR has better high temperature resistance and can improve the service life of Timing belt under high temperature and dynamic conditions, so the rubber for Timing belt is gradually developed from neoprene to HNBR.