A high-temperature O-ring consists of material that can function effectively at elevated temperatures. Damaged O-rings and related performance issues common to O-ring failure at high temperatures can be directly attributed to incorrect material for the application. Every type of elastomeric material used for O-rings has its own temperature limits to function effectively. Exceeding these limits can lead to accelerated wear, loss of elasticity, and ultimately failure of the seal, resulting in leaks or system malfunction.
O-rings are a type of gasket used to join and seal mated surfaces in industrial and mechanical systems. When compressed between joined surfaces, the familiar doughnut-shaped component serves to reduce friction, resist pressure, and prevent leaks in dynamic applications. Any mechanical system whose parts require fluids, oils, or like lubrication to function also requires gaskets such as O-rings.
O-rings are manufactured, principally, of varying types of elastomers, which are rubber-like polymers regarded for their diverse mechanical properties such as elasticity, tensile strength, durability, viscosity, and weather and temperature resistance. Material selection for an O-ring is defined by its application requirements. Therefore, the best O-ring material for an application is the material best suited for the application. Correct material selection ensures that the O-ring mechanical properties are compatible with the sealing requirements for the device. Knowing which type of elastomer is compatible can be the difference between downtime and productive time. This is particularly important for O-rings to function in high-temperature applications.
How Increased Temperatures Can Affect O-Ring Function
Different types of O-ring materials have varying temperature ranges that they can withstand. Depending on the material, higher temperatures can have either a positive or detrimental effect on the properties of O-rings. That’s why exposing some types of elastomers to high temperatures can result in physical and chemical deterioration, adversely affecting O-ring function and performance in a given mechanical system.
Increased temperatures can alter material properties and promote compression sets, impact chemical compatibility, induce uneven thermal expansion, and, in general, push the O-ring beyond its performance limits. As an example, the material properties of the O-ring, such as its hardness and elasticity, can be affected, leading to a loss of sealing effectiveness. For engineers and designers alike, it’s essential to consider these factors when choosing O-ring materials for a mechanical system designed to operate at an elevated temperature environment.
The Effects of High Temperature on Elastomers
Elastomers have specific temperature ranges within which they can effectively maintain their elasticity and sealing properties. When temperatures increase beyond these ranges, the material properties can change, which may lead to potential issues with sealing effectiveness. For example, at higher temperatures, some elastomeric materials will soften and succumb to compression set, meaning that they become prone to permanent deformation, reducing the O-ring sealing effectiveness and ability to maintain proper contact and compression against mating surfaces.
There is also the effect of thermal expansion when an O-ring’s elastomeric materials are subjected to increased temperatures. Such materials can expand or contract at different rates with the temperature change. In mechanical systems where temperatures rise, the laws of physics dictate that the O-rings elastomeric material will undergo thermal expansion. Depending on the properties of the material comprising the O-ring, it will either expand equally or unequally. Regarding the latter, this can adversely affect contact pressure and impact the integrity of the seal.
High-Temperature O-Ring Materials
High-temperature O-rings are a type of O-ring that can withstand temperatures of 150°C (302°F) or more. The selection of materials for high-temperature O-rings is limited due to the extreme conditions. Factors such as temperature range, chemical compatibility, and pressure requirements play a role in determining the best O-ring for high-temperature applications. That said, three of the best heat-resistant elastomers ideal for O-rings in high-temperature applications are Viton (FKM), PTFE, and silicone. Here’s why.
Viton, or FKM, O-rings are very durable and regarded for their exceptional resistance to high temperatures, petrol, diesel fuels, silicone oils and greases, many chemicals, aliphatic and aromatic hydrocarbons, and mineral oils and greases, aliphatic, aromatic, and also special chlorinated hydrocarbons,. The material is suitable for temperatures ranging from -26°C to 204°C (-15°F to 400°F) and performs well in high vacuum applications.
O-rings made from PTFE (polytetrafluoroethylene) are capable of withstanding high temperatures up to 250°C (482°F). They offer resistance to all known acids, alkalis, and solvents, and exhibit excellent chemical resistance, low friction, and good electrical properties.
Silicone offers good flexibility and resistance and can withstand a wide range of temperatures, from -84 to 232°C (-120°F -450°F), and can handle even higher or lower temperatures for shorter periods. It offers chemical resistance to oxidizing chemicals, some acids, ammonia, and isopropyl alcohol, and has exceptional UV light, ozone, water, oxygen, moisture, and steam resistance. Silicone’s non-toxic biocompatibility makes it an ideal material for medical seals and devices.
Contact Manufacturer’s Rubber and Supply
It’s important to select the appropriate O-ring material based on the specific requirements of the application to ensure optimal performance and longevity. Manufacturer’s Rubber and Supply is a premier manufacturer of rubber products and offers a wide selection of O-rings. No matter what your project is, we can help. For more information on which material is best suited for your O-ring application, contact us today.
