The humble but hard-working O-ring is the workhorse of industrial sealing applications.
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The humble but hard-working O-ring is the workhorse of industrial sealing applications. They can mean the difference between machinery running optimally and catastrophic system failures. Choosing the correct elastomer material is crucial to ensure you have the right O-ring for the job. In this article, TRP Polymer Solutions compares Viton® O-rings vs silicone O-rings to demonstrate their respective features, benefits, and drawbacks.
O-rings are arguably one of the most commonplace seals used in industry. These unassuming but supremely useful seals can be specified to handle static or dynamic sealing operations in pneumatic and hydraulic applications, and are employed to prevent leaks in everything from valves to cylinders.
The choice of elastomer will, perhaps unsurprisingly, play a pivotal role in the characteristics and subsequent deployment of an O-ring. With that in mind, let’s explore the various benefits of silicone O-rings and the comparative benefits of Viton® to determine which is the ultimate sealing material.
Viton® is actually a brand name coined by chemical giants DuPont for their particular blend of fluoroelastomer (FKM). Like Hoover, Viton® has become somewhat of a catch-all term for fluoroelastomer rubber. However, for the purposes of this article, we will refer to this rubber material by its proper chemical name, fluoroelastomer and its shortened derivative, FKM.
Fluoroelastomers are characterised by their strong carbon-fluorine bonds, which imbue them with exceptional chemical, thermal, and oxidation-resistant properties. The beneficial traits of fluoroelastomers make them ideal for extreme applications involving fuel and chemical transport and handling. They are also suitable for high-temperature and explosive environments as seals for the oil and gas sector.
Standard Viton® O-rings are likely to perform less effectively at temperatures below -20°C, at which point they can become somewhat hard and inflexible. However, special FKM compounds can provide low-temperature capabilities down to -40°C. Additionally, variants of the Viton® material, such as Viton® Extreme, offer an increased resistance to strong acids, amines, and steam for more demanding environments.
Silicone is comprised of a backbone of silicon atoms with alternating oxygen atoms. It’s these high-energy silicon-oxygen bonds that make silicone more heat-resistant than many other elastomers and more resistant to ozone, UV radiation, and many oils. Silicone is renowned for having one of the widest working temperature ranges of any elastomer, as well as excellent flexibility and low compression set characteristics.
Silicone O-rings can also be compounded to be flame-retardant, electrically resistant, and conductive. On the downside, silicones offer poor tensile strength, poor abrasion resistance, and poor tear resistance. As such, silicone O-rings should only be reserved for static sealing applications.
In conclusion, silicone O-rings can be applied to high-temperature applications or where damage from the elements may be a factor. However, the aforementioned lack of tear and abrasion resistance restricts them to static rather than dynamic applications. For a cost-effective static sealing solution, silicone makes perfect sense as your seal material of choice.
However, if you require a more versatile material capable of both static and dynamic sealing, then FKM is the clear winner. The relative added expense of a Viton® O-ring is paid back through greater operational efficiency, extended service intervals, reduced maintenance costs, and more reliable sealing. With less risk of costly unscheduled downtime, FKM O-rings provide an exceptional return on investment.
As expert elastomer manufacturers, TRP Polymer Solutions can develop the perfect O-ring or custom rubber moulding component for you. For advice and guidance about our various types of polymer, or to discuss your application requirements in more detail, contact TRP Polymer Solutions today on +44(0)1432 268899 or email sales@trp.co.uk.
6 Jan 2020 • 
4 min read
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