The chemical formula for Nitrile Butadiene Rubber (NBR) cannot be represented by a single, concise formula because it is a copolymer consisting of varying ratios of two monomer units: butadiene (C4H6) and acrylonitrile (C3H3N).
Butadiene contributes units of:
Acrylonitrile contributes units of:
In the NBR copolymer, these monomer units are randomly linked together in a long chain structure. The actual ratio of butadiene to acrylonitrile units will depend on the specific grade of NBR being considered, which can range from a lower percentage of acrylonitrile (around 18%) for greater flexibility to a higher percentage (up to 50%) for improved chemical resistance, especially to oils.
Therefore, instead of a fixed formula, NBR is better described as a statistical copolymer with a general structure that includes both butadiene and acrylonitrile repeat units in varying proportions. The exact composition directly influences the properties of the final material, such as its oil resistance, elasticity, and hardness.
