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Temperature Ranges for Various Materials: NBR to PTFE

Cliff • April 24, 2019

Sealing materials are selected for many different reasons. The application dictates the style of sealing. But fluids, pressures, and cycle times all play a prominent role in seal and material selection.

When we add in temperature, this factor often directs us to the types of materials that can survive the application. Read on to learn how we choose sealing materials based on operating and interface temperatures.

Sealing Material Applications

Let’s start out with the most basic material, NBR or Buna-n rubber. The standard temperature range for this material is -40F to 250F. With compounding, this range can be extended to -65 and 300F, but rarely operates at both extremes — and always as a special compound.

With rubber compounds, we must always be cognizant of the fluid in contact to ensure chemical compatibility. It’s important to note that rubber contact seals are best suited for static applications.

Other elastomers, such as silicone, normally travel between -65 and 450F — but don’t handle hydrocarbon fluids. Switching to fluorosilicone has a broader temperature range of -100 to 350 or 400F, and handles hydrocarbon fluids. In this case, availability becomes a problem.

When we talk about elastomers in sealing, the user must be selective within a range of factors. The temperature boundaries can often create other problems in elastomers, such as compression set or swell when combined with fluids.

We use elastomers in sealing as a primary seal and often as a secondary seal in a system. Even if the seal is static, it can still suffer from issues of elevated or frigid temperatures.

Polymer Materials

Polymer materials open a wide range of sealing possibilities. But even the most rigid of polymers needs to remain flexible throughout its operating range and chemically compatible.

While polymers like Teflon can operate between -400 and 500F, there are many physical changes that cause the material to either be too rigid to seal or have such a large loss of physical properties that it could become useless in an application.

An example would be Ultra High Molecular Weight Polyethylene , UHMW, which provides great sealing in air and water and many chemicals but loses structural integrity above 180F. Urethanes are up in the 300F.

We have sealing applications that exceed 1000F and we often turn to carbon seals like the triple ring seal. The requirements for long life are often care in manufacturing the gland with excellent surface finishes.

If all our sealing will occur over 700F and there’s no oxygen present, Polyimide materials often do an excellent job. But as temperatures cool, this material becomes less compliant.

PCTFE

Want to go to -460F (close to absolute zero), Polychlorotrifluoroethylene, or PCTFE is what you’re looking for. The caveat to all these polymers with temperatures that exceed the ability of most elastomers are metal springs.

Eclipse Engineering designs seals from the application up. The use of elastomers, polymers, carbon, and metal springs are just a few of the tools we use to solve sealing problems.

In designs where we can see over 700-degree temperature swing, it’s important to realize the interaction of the seal with the hardware. As the hardware is going through these swings, we must accommodate the growth and shrinkage of dissimilar materials when designing a sealing solution.

Having a full range of materials allows us to design solutions for your specific needs. The engineering staff at Eclipse has experience with all the materials mentioned to create a solution specific to your needs.

We also manufacture using various grades of elastomers, custom blending of any of the polymers to handle varying amounts of temperature change with spring candidates ranging from a simple Buna-n O-ring to a sophisticated spring energized seal.

Case Study: Angled Spring Grooves for Custom Spring Energized Ball Seats

By Doug Montgomery • February 13, 2025
Learn how Eclipse Seal’s custom spring energized ball seats with angled grooves improve performance

Case Study: Dual Lip Crimped Case Seal in High Speed Rotary Vacuum Application

By Doug Montgomery • January 17, 2025
Eclipse deals regularly with challenging sealing applications from all industries. High pressures and speeds create unique sets of conditions where seal design and material properties are pushed to the limit. While reciprocating applications can certainly test seals to the edge of capability, often times rotary applications can present the greatest challenge to seal integrity and wear life. Unlike reciprocating configurations where the seal is acting on a different part of the shaft or bore throughout it’s operating range, rotary seals must operate on the same sealing area continuously. This makes things like heat rejection much more difficult, especially in unlubricated or dry running applications. Extreme localized heating can have negative affect on both seal and hardware life. Rotary applications also pose sealing difficulties due to the simple fact that surface speeds can be much higher than in reciprocating systems. A simple electric motor can operate at very high rpm, while long stroke, high speed reciprocating machinery is a major piece of equipment that is far less common (though Eclipse also has sealing solutions in a number of these situations). A customer approached Eclipse with an application that was beyond the scope and capability of any standard, off-the-shelf rotary seal. This sealing system would require a combination of both wear resistance in high-speed rotary, as well as excellent leakage control and sealability. Two factors that, more often than not, work in opposition to each other. The Customer Issue The customer was developing a test system that required an electric motor shaft passed through the wall of a large vacuum chamber. The testing apparatus needed a sizable motor to meet the speed and torque requirements. Adapting the motor to operate inside the chamber would not be practical due to contamination and motor cooling concerns. Therefore, the motor would have to be placed outside the chamber and a driveshaft would have to go through the chamber wall. Which, of course, would need a seal. Operating Conditions:
 Rotary Shaft Seal
 Shaft Diameter: 2.5”
 RPM: 7,500 RPM - unlubricated
 Pressure: Vacuum internal side / 1 ATM external side Temperature: 40° - 90°F The customer knew any kind of off-the-shelf rotary seal with a rubber element would not last any amount of time in the combination of speed and a dry running condition. They also knew a single lip PTFE seal would likely not meet their leakage requirements. Therefore, they turned Eclipse for a custom sealing solution.

Case Study: PEEK Spring Energized Seal in a High Temperature/High Radiation Application

By Doug Montgomery • November 25, 2024
Eclipse has engineered sealing solutions for applications all over the planet and in a plethora of environments. From the bottom of the ocean to orbiting the earth, Eclipse is challenged by the unique conditions in each application. Whether it be extreme temperature and pressure or severely caustic or abrasive media, Eclipse has a solution for most every sealing problem. One distinct environment presents a particularly challenging set of circumstances for seal design – high radiation. Eclipse’s primary seal material choice for many applications is PTFE and PTFE blends. With all the wonderful attributes PTFE possesses as a seal material, radiation resistance is not one. In high radiation environments PTFE’s properties can degrade to essentially rule it out as a suitable material. The options for effective sealing materials that are also radiation resistant becomes very limited. The seal designer is therefore confronted with creating a seal that is expected to perform in every way a typical PTFE seal operates, out of materials that are not as favorable to sealing. This is where Eclipse’s engineering experience and expertise in seal design come to the forefront. The Client's Issue Eclipse was approached by a customer that was looking for a seal solution for a sensor used in a nuclear application. It would be operating in an environment with both high temperature and high Gamma radiation. Operating Conditions:
 Reciprocating Rod Seal
 Rod Diameter: Ø1.000
 Stroke: 1.5”
Cycle Rate: 2-4 cycles per minute
 Media: Air, Salt Water Mist
 Pressure: 100 PSI
 Temperature: 70° to 450°F
 Gamma Radiation Exposure: 10^6 rads

Case Study: MicroLip™ – Robust Rotary Sealing in Cutting-Edge Robotics

By Doug Montgomery • November 14, 2024
Technological advancements in the area of robotics have led to more and more life-like creations existing only in works of science fiction a few decades ago. Development in autonomous logic processing and sensing allows bipedal robots to walk over uneven ground, up and down stairs, open doors and carry loads. Fast response to dynamic and unpredictable real-world environments is critical for the future use of robots in true-life service and practical employment in the years to come. While software and sensor development remain the primary focus of most research, the physical mechanics of next-gen robotics are also continually progressing. Physical components and control systems such as hydraulic pumps and cylinders, servo motors, and structural members are under pressure to continually be lighter, stronger, more efficient and less expensive. Increased demands on the physical components facilitate the need for innovative solutions in design and material usage. Advancements in construction and technology have spilled into all areas of robotic mechanisms and the many seals located throughout the system need to meet the challenges of tomorrow. Eclipse has been at the forefront of this research and has developed innovative solutions pushing the boundaries of conventional sealing devices. MicroLip™ by Eclipse is a prime example of most demanding applications forging new technologies in the sealing world. The Client's Issue Eclipse was approached by a leading robotics company looking for a sealing solution operating under a challenging set of conditions. While many components of tomorrow’s robotics are now controlled and actuated by servo/stepper motors and various electronic devices, the heaviest and most powerful movements are still driven by traditional hydraulics. The constant demand for more powerful hydraulic actuation in ever deceasing size and weight requirements has put tremendous strain on component design. But if robots are to progress to the point where they are usefully employed in the world, high power in a compact design is necessary. A robot, for example, used to survey and assist in a disaster zone too unstable for normal rescuers, must fit through doorways and over obstacles yet still be physically strong enough to render assistance. Large hydraulic systems are capable of moving extremely heavy loads but size and weight constraints of a humanoid size robot limit potential. The robot’s internal power supply to drive all components is also a limiting factor. Our client was developing a new hydraulic pump to drive all major motion aspects of their robotic systems. Their main objective was to minimize the pump’s physical size as much as possible while increasing output and improving power consumption efficiency. This means higher pressures and speeds on increasingly smaller and lighter components. Application Parameters: Shaft Diameter: Ø9.5mm Seal Housing Envelope: 5mm radial cross-section by 6mm axial width Rotational Speed: 3,500 RPM nominally; 6,000 RPM max Operating Pressure: 125 PSI min, 225 PSI nominal, 350 PSI max Surface Finish: 0.04µm Media: Hydraulic Oil While the above combination of pressure and speed might present difficulties for any conventional seal alone, the client’s extremely small physical envelope to house the seal further complicated the matter. If that wasn’t enough, the application presented the additional sealing challenge of up to 0.003” [0.08mm] of shaft runout. As part of the downsizing of all components in the pump, shaft support bearings were minimized leading to the possibility of runout. The wobbling effect of the shaft creates problems as the sealing lip has follow a moving, uneven mating surface, therefore potential leak-paths are created. Wear life can also be compromised due to higher concentrations of uneven loads. The combination of high pressure, high speed, high runout and minimal gland size present a worst-case scenario for a typical seal. Unsurprisingly, the client faced leakage of hydraulic fluid after only short periods of service with any conventional seal they had tested. Eclipse knew the had the perfect solution for this application. One developed to handle such extreme rotary sealing conditions: MicroLip™.
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