Rubber nomenclature: Buna-N is the common name for which elastomer family?

Introduction / Context:Trade and historical names for rubbers can be confusing. “Buna-N” appears widely in seals, gaskets, and fuel-system components. Being able to translate these names into chemical families is essential for compatibility and property selection.

Given Data / Assumptions:

• Buna-N is widely used in oil-resistant applications.
• Options include several common elastomer families.
• We assume standard nomenclature used in industry.

Concept / Approach:Buna-N stands for butadiene–acrylonitrile copolymer, known generically as nitrile rubber (NBR). Butyl rubber is isobutylene-isoprene copolymer, neoprene is polychloroprene, and thiokol refers to polysulfide rubbers. NBR’s acrylonitrile content imparts oil and fuel resistance, making it prevalent in automotive and industrial seals.

Step-by-Step Solution:Decode Buna-N → butadiene + acrylonitrile → NBR.Match properties → oil/fuel resistance typical of nitrile rubber.Eliminate butyl, neoprene, and polysulfide as different chemistries.

Verification / Alternative check:Seal catalogs and materials handbooks list Buna-N and NBR interchangeably, with grades defined by acrylonitrile percentage and cure system.

Why Other Options Are Wrong:Butyl: gas impermeability focus; chemistry differs.Neoprene: polychloroprene; halogenated rubber with different compatibility.Thiokol: polysulfide; notable for solvent resistance and odor, not NBR.

Common Pitfalls:Assuming “Buna” always means butyl; historically “Buna” was used broadly, but Buna-N specifically denotes NBR.

Final Answer:Nitrile rubber