Which material is a rubber or plastic used as a seal?

• A. O-ring
• B. Elastomer
• C. Sealant
• D. Gasket

Answer: (B)

Elastomer is a rubbery polymer with elastic, reversible deformation, which makes it perfect for sealing. When you compress an elastomer, it flows slightly to fill tiny gaps and then rebounds to maintain a tight seal as pressure changes. This combination of deformability and recovery, along with chemical and temperature resistance in various formulations (natural rubber and synthetics like nitrile, silicone, neoprene, and fluorinated elastomers), is exactly what you need in seals. O-rings and gaskets are common seal shapes made from elastomer, but they’re outlines of how a seal is used. A sealant, on the other hand, is a substance applied to joint surfaces to fill gaps and harden, not the rubber-like material that forms the seal itself. So the material category described here is elastomer.