Gaskets /Seals
“A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression. Gaskets allow "less-than-perfect" mating surfaces on machine parts where they can fill irregularities. Gaskets are commonly produced by cutting from sheet materials, such as gasket paper, rubber, silicone, metal, cork, felt, neoprene, nitrile rubber, fiberglass, Polytetrafluoroethylene (otherwise know as PTFE or Teflon) or a plastic polymer (such as polychlorotrifluoroethylene).”
“Gaskets for specific applications, such as high pressure steam systems, may contain asbestos. However, due to health hazards associated with asbestos exposure, non-asbestos gasket materials are used when practical.”
“It is usually desirable that the gasket be made from a material that is to some degree yielding such that it is able to deform and tightly fills the space it is designed for, including any slight irregularities. A few gaskets require an application of sealant directly to the gasket surface to function properly.”
(Wikipedia, Gaskets, 11/9/2011)
“The possibilities for use of these elastomeric materials in the area of seals range from static seals such as, for example, cylinder head, valve cover or oil sump gaskets, seals for manual transmissions and automatic transmissions, O-rings, seals in the area of intake manifolds and exhaust gas recirculations to dynamically stressed sealing elements such as, for example, piston sealing rings, in particular, also so-called bonded piston seals.” [Hornig, US Patent 8,048,964 (11/1/2011)]