An O-ring material selection guide
Posted on 19/05/2016 Category: O-Rings
O-rings are common seals used in many manufacturing industries. With such a broad range of materials available, it can be tricky to select the appropriate material for any given project. So Martin’s Rubber has compiled this useful O-ring material selection guide, to give you a clear insight into the advantages and disadvantages of common O-ring materials. O-rings are an ever-present product across many industrial applications these days. One of the great advantages of O-rings, which makes them so prevalent, is that they can be manufactured from a wide range of elastomers to give an exceptionally durable and functional final product. However, as we know, too much choice can sometimes be a bad thing. In fact, when it comes down to it, what really sets one O-ring material apart from another? Well, short of talking to an experienced Martin’s Rubber adviser – which should always be your first port of call for the most comprehensive advice and guidance – read on for a detailed O-ring material comparison, to find out more about the various qualities of common O-ring elastomers.
O-ring material comparison
Viton® is an all-round material capable of handling a diverse array of applications, particularly sealing jobs involving movement. It is suited for silicone fluids and gases, petroleum oils, acids and some halogenated hydrocarbons. Viton® isn’t recommended for Skydrol, ethers with low molecular weight, amines, esters or hot hydrofluoric acids. Viton® O-rings are extremely versatile, finding a home in many chemical processing, automotive and appliance applications.
Nitrile (Buna-N) O-rings
Nitrile or Buna-N O-rings produce general purpose seals that are tear-resistant and can withstand abrasive treatment. Nitrile O-rings, which have a temperature range between -54 and 149 degrees Celsius, are suitable for use with water, petroleum oils and some hydraulic fluids. Nitrile O-rings are not advisable for use with automotive brake fluid, ketones, phosphate ester hydraulic fluids, and nitro and halogenated hydrocarbons. Bear in mind that nitrile’s inherent ozone and weather resistance is not infallible, though it can be strengthened through compounding. Nitrile performs well in applications with limited temperature and resistance requirements.
Neoprene, which is classified as a general purpose elastomer, is unusual in that it is moderately resistant to petroleum oils and weather (ozone, UV, oxygen). Neoprene O-rings are therefore uniquely qualified for certain sealing applications where many other materials would fail. It has relatively low compression set, good resilience and abrasion, and is flex cracking resistant. Neoprene shares the same operational temperature range as nitrile and is commonly used to seal refrigerants in air conditioner and refrigeration units. Some people can have an allergic reaction to basic neoprene.
Silicone O-rings perform well with water, steam or petroleum fluids and are sometimes used in high temperature fuel injection ports. They can operate within a temperature range of -84 and 232 degrees Celsius. Though silicone O-rings have been shown to withstand an extreme of -115 degrees Celsius during short periods of exposure. Silicone does, however, exhibit poor tear resistance, abrasion and tensile strength. It is therefore better suited for static, rather than dynamic, applications.
Ethylene Propylene Rubber (EPR) O-rings
Unlike Viton® O-rings, Ethylene Propylene Rubber (EPR) O-rings are suitable for use with corrosive Skydrol hydraulic fluid, as well as steam, water, silicone oils, brake fluids and alcohols. This material is known to display good heat and compression resistance. Similar to nitrile, EPR is not perfect for a wide-range of applications due to wear and tear issues. EPR O-rings have been used widely in the aerospace industry in hydraulic pumps.
PTFE encapsulated O-rings handle surface wear well, in addition to exhibiting corrosion and abrasion resistance, non-permeability, chemical inertness and low absorption. They can also operate within a wide temperature variance of between -73 and 260 degrees Celsius. Pure PTFE O-rings are very rigid and hard to apply, which makes them more suited to static applications. PTFE O-rings are often used in automotive steering devices and paint guns.
Polyurethane is well regarded for its all-round general toughness, as well as for its notable abrasion and extrusion resistance. O-rings made from this material would not be suitable for applications requiring good compression and heat resistance. The latter is due to a narrower operational temperature range of between -54 and 100 degrees Celsius. Polyurethane O-rings are often used for hydraulic fittings, cylinders and valves, pneumatic tools and firearms. Now that you’ve chosen your preferred O-ring material, are you having trouble sizing it? Read another one of our recent blogs to find out more about our handy O-ring size chart. Find out more about our O-Ring products by speaking to us on 023 8022 6330, or [email protected].