Some materials survive extreme environments while others redefine what “extreme” means. From cryogenic hydrogen at -459°F to continuous operating temperatures of 500°F, from high-speed rotary shafts approaching 100,000 RPM to chemically aggressive process media, modern sealing applications demand more than incremental improvement. They demand stability, predictability, and performance under conditions where traditional elastomers begin to fail.
PTFE seals occupy that space.
This article examines why PTFE continues to be specified in aerospace, chemical processing, food and pharmaceutical systems, and high-speed rotary equipment. This article explores its extreme temperature stability, low-friction tribological behavior, chemical inertness, high-speed capability, long-term reliability, and the ability to tailor performance through fillers and spring energization. The goal is not simply to list advantages, but to understand how those properties translate into measurable engineering performance.
Extreme Temperature Stability
One of the properties that sets PTFE seals apart is their ability to maintain mechanical integrity across a wide range of temperatures, from -459°F (-273°C) to +500°F (+260°C). In addition, they resist melting and degradation at continuous operating temperatures of 500°F, including spikes up to 600°F. High temperatures are not the only area where PTFE excels. PTFE seals remain flexible and retain sealing force even in the presence of cryogenic fluids (e.g., liquid hydrogen, deep space). They successfully prevent the embrittlement problems that are so common in traditional elastomeric seal solutions. In addition, PTFE has a very low coefficient of thermal expansion that supports dimensional stability even during rapid temperature cycling.
Superior Tribological Properties
PTFE also offers an extremely low coefficient of friction, as low as 0.04. This property reduces torque requirements and power loss. PTFE also deposits a microscopic film on the mating surface, creating a PTFE-on-PTFE interface that minimizes wear and enables dry running. Dry running is an extremely useful feature of PTFE, meaning it can run without external lubrication and eliminate stick-slip even after long periods of inactivity.
Chemical and Environmental Resistance
PTFE is one of the most chemically non-reactive polymers. It is non-reactive with almost all industrial chemicals, including aggressive acids (hydrochloric and sulfuric), solvents, and hydrocarbon fuels. Furthermore, it does not become brittle, swell, or degrade when it is exposed to corrosive media. Virgin PTFE grades are FDA, USDA, and 3-A Sanitary approved for food, dairy, and pharmaceutical use. PTFE is hydrophobic: it repels water and resists moisture buildup, making cleaning and sterilization much easier. Finally, PTFE is ideal for aerospace and high-vacuum environments because of its minimal outgassing, which prevents the contamination of sensitive optics or electronics.
High-Speed and Pressure Performance
PTFE rotary shaft seals can handle shaft surface speeds around 6,900 rpm and rotational speeds on the order of 100,000 RPM, which exceeds the limits seen in traditional elastomeric seals. They can also handle pressures up to 100-150 psi, and when BUR or sprig-energized options are used,, they can withstand significantly higher pressures.
Operational Longevity and Reliability
PTFE seals have an unlimited shelf life, unlike traditional rubber seals, which age and degrade during storage. In addition, the self-lubrication and wear resistance of PTFE seals reduce unexpected downtime and maintenance downtime. In addition, non-abrasive grades of PTFE can protect mating shafts from grooving and other surface damage that compromise seal performance. Finally, the low friction of PTFE reduces energy consumption.
Customizability via Fillers and Design
Another key benefit of PTFE is that it can be compounded with fillers to target specific material properties.
- Glass Fiber: Increases wear resistance and compressive strength
- Carbon/Graphite: Improves thermal conductivity and allows for use in steam/water, and is safer for softer shafts
- Molybdenum Disulfide (MoS₂): Increases hardness and lubricity for high-pressure dry running
- Polyimide: Ultra-low friction for use against soft mating surfaces like aluminum
In addition, metal springs can be added to provide a constant sealing force and compensate for seal wear, hardware misalignment, or thermal contraction.
Conclusion
In high-performance applications, failure rarely stems from a single variable. It emerges when materials, load, temperature, motion, and environment are not aligned. PTFE provides the stability needed to bring those variables into balance.
To learn more about PTFE options for sealing solutions, contact the PTFE seal experts here at Advanced EMC. We are here to help you from the initial design stages through to testing and implementation.
