Elastomeric Gaskets are made of one type of solid rubber which is either cut from a sheet/roll or moulded/extruded to a specification. These gaskets are suited for low pressure, low heat environments and will create a seal with a low bolt load. This is ideal for flanges that use low grade low quality bolts and/or non-asme flanges and joints. O-rings fall into this class of gasket and are particularly suited to tongue and groove applications.
The use of these gaskets are limited to the operational working conditions that the type of rubber exhibits. And since rubber gaskets will not compress, only deform, excess bolt load will only extrude the gasket out of position into the inner diameter of the flange causing a disturbance of the process fluid and cause the gasket to lose thickness and allow a loss of seal.
Cellular elastomers such as foam/sponge are made by mechanically or chemically expanding uncured rubber compounds. Closed cell foam is made with separate cells of trapped gas within its structure. This makes the foam highly compressible and impermeable to fluids. They are ideal for use as weather seals.
Elastomeric gasket can also have a reinforcing fabric material to provide higher strength. They can contain one or more plies of the material which is made of several fibers, typically nylon, cotton, polyester, as well as the less frequently used asbestos and glass.
Common Rubber Gasket Materials
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Natural Rubber – Excellent physical properties including abrasion and low temperature resistance. Poor resistance to petroleum-based fluids.
Urethane – Good aging and excellent abrasion, tear, and solvent resistance. Poor high temperature properties.
Neoprene – Good weathering resistance. Flame retarding. Moderate resistance to petroleum-based fluids. Good physical properties.
Nitrile – Excellent resistance to petroleum-based fluids. Good physical properties.
Butyl – Very good weathering resistance. Excellent dielectric properties. Low permeability to air. Good physical properties. Poor resistance to petroleum-based fluids.
EPDM – Excellent ozone, chemical, and aging resistance. Poor resistance to petroleum-based fluids.
Styrene Butadiene (Buna-S, SBR) – Excellent abrasion resistance and low temperature properties. High resilience.
Silicone – Excellent high and low temperature properties. Fair physical properties.
Hypalon – Excellent ozone, weathering, and acid resistance. Good abrasion and heat resistance. Fair resistance to petroleum-based fluids.
Viton – Excellent oil and air resistance both low and high temperatures. Very good chemical resistance.1 “Sheet Rubber Handbook – Gasket and Packing Materials”, Rubber Manufactureers Association(RMA) & The Rubber Association of Canada