Rubber gaskets are elastic elements used to mechanically seal tiny gaps between two mating surfaces or joints. Examples of these surfaces are flange faces of pipes and fittings, mating surfaces of automobile cylinder heads and engine blocks, fuel tank edges and covers, door edges, frames, etc.

Rubber gaskets seal surfaces by flowing into and filling in surface irregularities of rigid parts. The sealing effect is produced by a component that exerts a compressive force that plastically deforms the gasket.

The sealing ability of rubbers is due to their elasticity. Natural or synthetic rubber belongs to a family of materials called elastomers. Elastomers are a class of highly elastic polymers produced by crosslinking long polymer chains into an amorphous structure.

The intermolecular forces between polymer chains are relatively weak, which allows them to reconfigure when pressure is applied. Due to this property, the elastomeric gasket can easily conform to the contours of the surface, resulting in a tight seal.