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“Materials” are the foundation of our technology. Every day, people deal with products that possess seals and they generally know very little about the materials with which they are made. For example, plastic is a comparatively new material and has long been considered to be a “wonder substance”. But why is plastic so flexible and how are the various mixtures differentiated from one another? When is a silicone seal better than one made of polyurethane or rubber?
NBR – Nitrile Rubber
NBR is the abbreviation for nitrile butadiene rubber. This is a synthetic rubber that was developed during the 1930s. It is fabricated through the co-polymerization of acrylonitrile (ACN) (polar building block) and 1.3-butadine (nonpolar building block). Its attributes mainly depend on its ACN content.
The manufacturer can vary the content and thus produce different types of the material. In the process, the ACN content determines the balance between media resistance and low-temperature flexibility. Low ACN content produces a low glass transition temperature but also leads to greater swelling in oils and fats. As the ACN content increases, this behavior reverses direction – due to the polar components in the polymer.
Nitrile rubber exhibits superior mechanical strength with high elasticity as well as good deformation behavior in a temperature range between -30 °C and 100 °C. Its relatively low heat resistance can be traced to the presence of reactive double bonds. It is used for oil- and fuel-resistant seals such as Simmerrings®, O-rings and frame seals. The use of NBR marked the arrival of elastomers as a sealing material particularly in general industry. It is also employed in the auto industry.