The humble and versatile 'O' ring is an exceptionally good sealing device. That is the reason why these versatile O rings has made its way in diverse applications ranging from use in garden hose coupling to say the critical aerospace industry. Specialty O-ring seals are some how identical in shape to say a thick rubber band. They are usually round, but can be made available in oval, rectangular, oval, or trapezoidal shapes for making a watertight seal. Extruded O-Rings are manufactured from extruded cords from different types of rubber like Neoprene, EPDM, Silicone, Fluoroelastomer. They are manufactured using close tolerances and generally extruded in long and continuous lengths. (Image showing rubber O ring).

Parameters of O-Rings
Some of the parameters of the material used for extruded O rings are given here.

• Resistance to gases and oils
• Resistance to acids
• Resistance to permanent compression
• Extremely close tolerance
• Resistance to ozone
• Broad range of temperature
• Good Tensile strength

Materials for O rings
Here a brief discussion is made about the different types of rubber that is conducive and profitable for making O rings form extruded profiles.

Natural rubber
Natural rubber displays properties that makes it a preferred product for use in O rings. Some of this properties are high strength along with resilience. It shows good resistance towards abrasion, set and castor based fluids. It has good overall low temperature performance. On the negative side, natural rubber is not known for good heat resistance, weathering properties along with a limited resistance to oils that are based on minerals and aromatic fluids.Perhaps that is the reason why these days natural rubber is being increasingly replaced by synthetic polymers in majority of fluid seal applications.

Styrene butadiene rubber (SBR)
Another of extremely versatile rubber that is put to good use for extrusion applications. It is known by another name that is of Buna S. SBR is essentially a copolymer of butadiene and styrene. Styrene butadiene rubber was basically developed to act as a substitute for natural rubber. That is the reason why most of its properties are identical to that of natural rubber. Coming to the advantages it shows good temperature resistance, along with the a stable price. They are ideal for automotive applications.

Polychloroprene (CR) or neoprene
Neoprene as a material for O rings are known to display excellent resistance to weathering as well as ageing. Along with that it has reasonably good properties in terms of strength, resilience and abrasion resistance. However Neoprene shows some sort of limited resistance to fluids that are aromatic mineral based. Such all these properties make Neoprene a good option for outdoor applications.

Ethylene propylene rubber (EPDM)
Ethylene propylene rubber is basically a copolymer or terpolymer. Properties that makes them suitable for O ring application includes a good amount of resistance to weathering. Also it shows a good resistance to ozone, water and even to steam, which is considered a big challenge to elastomers. All these advantages make EPDM a preferred material for use in diverse applications including the all important central heating systems.

Silicone Rubber
Silicone rubber though not is a preferred choice for sealing applications like O rings but has certain advantages that includes its use in extreme temperatures, good resistance to chemical and weathering. It has a wide use in medical industry for being a material that is non toxic.