Selecting the right sealing material is crucial for reliable industrial sealing solutions. Among high-performance seals and gaskets, two popular polymer options are PTFE (Teflon) and PEEK. Both materials are known for their outstanding properties, but they differ in temperature tolerance, chemical resistance, mechanical strength, and ideal use-cases. This in-depth guide compares PTFE vs PEEK seals in terms of key differences and industry applications, and provides a material selection guide for engineers and procurement managers. We’ve also included visuals (tables, charts, and real-world examples) and an FAQ to address common questions about PTFE and PEEK sealing components.
Key Differences Between PTFE and PEEK Seals
PTFE (polytetrafluoroethylene) and PEEK (polyether ether ketone) are both high-performance thermoplastics, but they have distinct characteristics that influence their suitability for different sealing applications. Below we compare their temperature resistance, chemical compatibility, mechanical strength, friction/wear properties, and other factors:
Temperature Resistance
Both PTFE and PEEK can withstand high temperatures, but PEEK maintains integrity under load at temperatures where PTFE would start to deform. PTFE is generally stable for continuous use up to about 260°C (500°F). PEEK’s melting point is around 343–400°C, and it can operate continuously around 250–260°C, with short-term exposure up to ~300°C without losing its shape under stress. In other words, PEEK handles high-pressure, high-temperature (HPHT) conditions better. For example, at 250°C a PTFE seal under load may creep or extrude, whereas a PEEK seal of similar design would retain its form. PEEK’s superior thermal dimensional stability makes it ideal for high-stress, high-heat environments, whereas PTFE might require mechanical support (like a metal spring or housing) at the upper end of its temperature range.
At low temperatures, PTFE remains flexible (usable down to cryogenic ranges, -200°C or lower) and does not become brittle. PEEK is tougher at ambient and high heat, but is more rigid; it can endure cold conditions but may not have the same flexibility as PTFE in extreme cold. Both materials have a wide operating range, but if your application involves extreme heat with pressure, PEEK is often the safer bet, while for extreme cold or moderate heat PTFE performs excellently.
Chemical Compatibility
One of PTFE’s greatest strengths is its chemical inertness. It is often touted as the “most chemically inert polymer,” resistant to acids, bases, solvents, fuels, and corrosive media across a broad temperature range. PTFE seals and gaskets can handle virtually any chemical fluid or gas, making them ideal for chemical-resistant gaskets in aggressive environments. Only a few extremely reactive substances (like fluorine gas at high temperature, chlorine trifluoride, or molten alkali metals) can attack PTFE, which are rarely encountered in typical industries.
PEEK also offers excellent chemical resistance, though not quite to the universal level of PTFE. PEEK stands up well against most acids, hydrocarbons, oils, and solvents – even at elevated temperatures. However, strong acids at high concentrations can be an Achilles’ heel for PEEK. Notably, concentrated sulfuric acid will actually dissolve PEEK at room temperature, and PEEK can be attacked by halogens and strong oxidizing acids, especially at high heat. In practical terms, this means PEEK seals are unsuitable for applications like concentrated vitriol (H₂SO₄) handling, whereas PTFE would be preferred in such cases.
For most chemicals encountered in industries (hydrocarbons, water, steam, mild acids/bases, etc.), both PTFE and PEEK are highly resistant and often rated “A” (excellent) in compatibility charts. PEEK’s chemical resistance is often described as second only to PTFE. As a valve seat material comparison: PTFE has “very high chemical compatibility” and is even FDA-approved for food/pharma uses, only failing with elemental fluorine or strong alkalis; PEEK’s compatibility is similarly broad (also available in FDA grades) but “may fail when exposed to sulfuric acid”. In summary, for extremely corrosive or ultra-pure applications, PTFE is usually the first choice, while PEEK is a close second that trades a bit of chemical inertness for other strengths.
Mechanical Strength and Dimensional Stability
When it comes to mechanical properties, PEEK is significantly stronger and stiffer than PTFE. PEEK exhibits a high tensile strength around 90–100 MPa, compared to PTFE’s tensile strength of about 25–35 MPa. This means PEEK seals can withstand higher loads and internal pressures without deforming. Similarly, PEEK’s flexural modulus (~3900 MPa) is an order of magnitude greater than PTFE’s (~495 MPa), reflecting PEEK’s rigidity versus PTFE’s flexibility.
In practical sealing terms, PTFE is a softer, more pliable material, while PEEK is hard and rigid like an engineering plastic. PTFE will deform (cold-flow) under long-term load – for example, a PTFE flange gasket may creep over time if bolting pressure is high. PEEK has superior creep resistance, maintaining dimensional stability under continuous stress and high pressure. This makes PEEK ideal for seals that serve as structural components (back-up rings, anti-extrusion rings, bearing cages, etc.) since it can hold tight tolerances in a loaded assembly. In fact, PEEK is so mechanically robust that it’s often processed and machined with guidelines similar to metals. One trade-off is that PTFE’s flexibility allows it to conform easily to surfaces (helpful for achieving a seal at low contact pressure), whereas PEEK’s hardness may require more precise mating hardware.
For high-pressure applications, PEEK seals handle load better — for example, in valve seats for high-pressure valves, PEEK can outperform PTFE which is generally not recommended above ~350 bar (~5000 psi) without support. PTFE seals in high-pressure systems often incorporate metal or polymer energizers (springs, washers) to prevent extrusion, whereas a PEEK ring can act as a structural seal or anti-extrusion ring on its own. If your application demands structural strength, stiffness, or long-term dimensional integrity under load (e.g., a gasket that shouldn’t relax or a seal that must retain shape over years of compression), PEEK is the preferred material.
Friction and Wear Properties
PTFE is renowned for its extremely low coefficient of friction – it is one of the slipperiest solids. Virgin PTFE’s coefficient of friction is about 0.05, versus ~0.35 for PEEK. This means PTFE seals have excellent self-lubricating characteristics: they slide easily against mating surfaces, generate minimal heat from friction, and do not stick-slip. PTFE’s low friction is a big advantage in dynamic seals (like rotary shaft seals, valve stem seals, etc.), where it reduces wear on both the seal and the counter-surface. PTFE can even run dry in many cases, since it inherently lubricates the interface. This is beneficial for applications where adding lubricants is undesirable or impossible (e.g. oxygen service, food processing, or cryogenic environments where oils might freeze).
PEEK, on the other hand, has a higher friction coefficient – not nearly as slippery as PTFE. However, PEEK still has relatively low friction compared to metal; it can often be used in dry or marginally lubricated conditions and is considered a low-friction polymer (some PEEK grades are formulated to improve tribology). In fact, PEEK also exhibits self-lubricating behavior to a degree, especially when immersed in fluids like water or oil. Its friction is just higher than PTFE’s. That said, PEEK’s wear resistance is outstanding. PEEK can sustain high PV (pressure-velocity) conditions without galling or wearing out quickly. It handles abrasive wear and repetitive motion with minimal material loss, even in harsh environments like those with sand or particulates. PTFE is softer, so in unfilled form it can wear faster under abrasive or high PV conditions – though it wears with very low friction heat. To combat this, PTFE is often filled with reinforcements (glass, carbon, bronze, etc.) to increase its wear resistance and stiffness. Filled PTFE compounds are commonly used for wear rings, bushings, and long-life dynamic seals.
In summary, if low friction is the priority (e.g. for a fast-rotating shaft or where power loss must be minimized), PTFE is unbeatable. If resisting mechanical wear and deformation is the priority (e.g. a high-pressure piston seal or a heavily loaded bearing), PEEK’s hardness and wear resistance give it the edge. Many spring-energized seal designs actually use PTFE for the sealing lip (for flexibility and low friction) and PEEK or a harder polymer for backup components – leveraging the strengths of both materials in one assembly.
Other Considerations (Density, Electrical, Processability, Cost)
- Density & Weight: PTFE is significantly heavier (density ~2.15 g/cc) than PEEK (~1.30 g/cc). For weight-sensitive designs (aerospace, racing, etc.), PEEK offers weight savings of roughly 40% compared to PTFE . This is one reason PEEK is popular in aerospace — you get high strength without the weight penalty of metal or heavier polymers.
- Electrical Properties: PTFE is an excellent electrical insulator with a very high dielectric strength (~50–150 kV/mm) and low dielectric constant. It’s often used in high-voltage and RF applications for this reason. PEEK is also insulating (dielectric strength ~50 kV/mm) but not as superior as PTFE in this regard. In applications like sensors or connectors where electrical insulation and high temperature are needed, PTFE might be favored for insulation while PEEK might be used for structural parts around it. Both materials have minimal moisture absorption (especially PTFE, which is almost completely hydrophobic), helping them maintain insulation properties in humid or wet conditions.
- Processability: PTFE is processed differently (by compression molding and sintering) because it doesn’t melt and flow like a normal thermoplastic. It’s often sold as molded billets that are machined into seals or as skived tapes . PEEK is a true thermoplastic that can be injection molded, extruded, or machined from stock shapes. For custom seals in low volumes, both materials are typically CNC machined from rods/tubes. PEEK is a bit easier to machine precisely because of its rigidity (PTFE’s softness can make it tricky to hold tight tolerances without deformation). Overall, both are available in various forms (rings, billets, finished parts) from suppliers.
- Cost: Price is often a deciding factor. PEEK is an order of magnitude more expensive than PTFE. Sources estimate PEEK can be ~5–10× the cost of PTFE by weight. PTFE itself is not cheap compared to common plastics, but PEEK is truly a premium material. The high cost of PEEK has kept it as a niche polymer used only when its performance is absolutely necessary. Procurement-wise, this means if PTFE can meet the requirements, it will save a lot on cost. PEEK’s expense is justified in extreme environments where other polymers (even PTFE) would fail – often preventing costly downtime or redesigns. When budgeting for seals, consider that a PEEK seal or gasket might significantly increase material costs; however, it could also outlast a PTFE part under harsh conditions, potentially offsetting its price with longevity.
Examples of machined polymer seal rings (various sizes) that can be made from PTFE or PEEK. Both PTFE and PEEK are supplied as solid stock (rods, tubes, billets) which can be machined into seals, rings, valve seats, and other components. PTFE’s softness allows it to conform as a gasket, but often requires metal springs or housings for support in high-pressure seals. PEEK’s rigidity means PEEK rings can serve as structural elements – for instance, back-up rings, bushings, or connector insulators in oilfield tools and valves. In the image above, the white rings could represent virgin PTFE parts (commonly white), while the black/brown rings are likely PEEK or filled PTFE parts. This illustrates how both materials appear as finished ring seals ready for installation in equipment.
Summary of Differences
To summarize the key differences: PEEK offers greater mechanical strength, higher load-bearing capability at high temperatures, and excellent wear resistance, albeit at a much higher cost. PTFE provides unmatched chemical resistance and ultra-low friction, along with flexibility and good performance over a wide temperature span (especially in chemical and low-friction contexts). PTFE is generally preferred for applications requiring chemical inertness or electrical insulation, or where friction must be minimized. PEEK is chosen for applications requiring structural strength, high-pressure capability, and low deformation under stress. Often, the choice comes down to the specific demands of the application – as the next sections on industry use-cases will illustrate.
Industry Applications of PTFE and PEEK Seals
Both PTFE and PEEK have proven their value across a range of industries. However, each material has particular domains where it excels. Here we highlight how these materials are used in aerospace, automotive, oil & gas, medical/pharmaceutical, and general industrial manufacturing, and why one may be favored over the other in each sector.
Aerospace & Defense
The aerospace industry demands materials that can handle extreme temperatures, pressure differentials, and rigorous safety standards. PTFE seals are widely used in aerospace because they reliably perform across a huge temperature range (from cryogenic -260°C up to +260°C) and have inherent flame resistance. For example, PTFE is used in jet engine seals and aircraft fuel system components where temperatures cycle from very low (high altitude cold) to very high, and where low friction is needed to reduce wear. PTFE’s inherently non-flammable nature (high LOI and low smoke generation) is a bonus for aerospace safety. Common aerospace uses for PTFE include rotary shaft seals, hydraulic seals, backup rings, valve seats, and O-ring energizers in systems like turbine engines, auxiliary power units (APUs), gearboxes, flight control actuators, and environmental control units. In these roles, PTFE’s low friction prevents excessive heat build-up at high speeds, and its chemical inertness handles various aerospace fluids (hydraulic oil, jet fuel) without degradation.
PEEK is also a star player in aerospace, especially where metal replacement and weight reduction are goals. PEEK’s high strength-to-weight ratio and thermal stability make it suitable for structural components near engines or high-heat zones. For instance, PEEK is used in aircraft engine components, fasteners, and sensor housings that must withstand heat and vibration. Electrical connectors in aircraft often use PEEK as an insulator body to handle temperature plus mechanical strain, while minimizing thermal expansion that could loosen connections. In defense and space applications, PEEK finds use in cable insulation, pump housings, and even missile components, thanks to its ability to maintain properties under punishing HPHT conditions. Its lighter weight also improves fuel efficiency and payload capacity compared to metal parts.
Where each excels in aerospace: PTFE is typically chosen for sealing applications requiring flexibility and chemical resistance (fuel and fluid seals, low friction bearings in actuators, etc.), and for insulation in high-voltage systems. PEEK is favored for structural or semi-structural parts that see high stress and temperature (e.g. compressor seals, high-pressure valve seats, or replacement of aluminum components to save weight). Notably, both materials are often used together: e.g. a spring-energized PTFE seal might have a PEEK anti-extrusion ring backing it up in a high-pressure aircraft hydraulic actuator. This combination leverages PTFE’s sealing and PEEK’s strength for a robust aerospace seal assembly.
Automotive
Modern vehicles rely on advanced materials to improve performance and efficiency. PTFE seals have become a go-to solution in many automotive systems – you’ll find PTFE in fuel injection seals, fuel pump seals, power steering rack seals, A/C compressor shaft seals, and turbocharger seals. One reason is PTFE’s unbelievably low friction, which reduces energy loss and wear in engines and drivetrains. PTFE shaft seals in the engine (for example, crankshaft or camshaft seals) can endure dry running and moments of starved lubrication without damage, thanks to PTFE’s self-lubricating nature. They keep oil in and contaminants out with minimal drag. PTFE also stands up to the cocktail of automotive fluids – from engine oils and gear lubes to coolants and fuels – it’s essentially immune to these chemicals. Even aggressive fuel additives or new bio-fuels don’t faze PTFE seals, whereas some elastomers might swell or degrade.
Temperature in automotive applications is another factor: PTFE dynamic seals can survive engine bay temperatures up to 250–300°C (for example, near exhaust manifolds or in turbochargers) where many rubber seals would fail. In fact, PTFE rotary seals have been shown to retain their properties at temperatures up to 600°F (315°C) in abusive conditions. This high-temp endurance means PTFE seals won’t melt or lose spring force in hot engine environments, maintaining sealing even during hard driving. Additionally, PTFE’s performance at high surface speeds is valuable for things like transmission output shaft seals – they handle high RPM and surface velocity with minimal wear or heat generation. All these benefits translate to reliability and even environmental gains: vehicles using PTFE seals often have reduced emissions due to better sealing (no oil leaks, less friction means less fuel consumption).
PEEK is used in automotive as well, particularly in engine and powertrain components that see extreme stress. A key application is PEEK-based seals in internal combustion engines. For example, PEEK piston rings and sealing rings are employed in some high-performance engines. These rings endure the combustion chamber temperatures and pressures while maintaining their shape and sealing ability. PEEK rings have shown excellent leakage stability at high temperatures, meaning they keep a tight seal between the piston and cylinder even when the engine is running hot. The bonus of PEEK’s low friction helps reduce frictional losses in the engine, improving efficiency. Another area PEEK is making inroads is cylinder head gaskets. Traditionally, head gaskets are multi-layer steel, but engineers have developed composite gaskets using PEEK combined with PTFE for demanding engines. This PEEK-PTFE gasket material provides a tight seal between head and block while withstanding extreme heat and pressure cycles. It resists abrasion and is more forgiving (less risk of corrosion or adhesion to mating surfaces) than metal gaskets. The use of PEEK in these gaskets also means they can better handle the differences in thermal expansion, maintaining seal integrity through heat cycles.
Outside the engine, PEEK is used in automotive transmissions and EV drivetrains for components like thrust washers, electric motor insulation, and bearings, due to its high wear resistance and thermal stability. It’s also found in braking systems (e.g., ABS components) where high heat occurs, and in connectors and sensor housings throughout the vehicle for its durability and dimensional stability.
In summary for automotive: PTFE is typically selected for dynamic seals and any application needing low friction, chemical inertness, and heat resistance – such as shaft seals, fuel system gaskets, and emissions-related seals. PEEK shines in high-temperature engine parts and structural sealing roles – like those critical engine seals and gaskets that must hold up to combustion forces. Cost sensitivity in automotive means PEEK is used where absolutely needed (sports or luxury vehicles, or long-life components), whereas PTFE, being cheaper, is widely used in mass production for improved performance over traditional elastomers.
Illustration of a PTFE rotary shaft seal (blue component) used in an automotive engine. In automotive applications, PTFE seals are often utilized on rotating shafts (e.g., crankshafts or wheel hubs) because of their low friction and high temperature tolerance. The image above shows a cross-section of a PTFE lip seal in a housing, demonstrating how PTFE can bridge the gap between traditional elastomer seals and full mechanical seals. Such PTFE shaft seals keep oil in and dirt out of engines, transmissions, and differentials, even at high RPMs and temperatures that would cause rubber seals to harden or crack. Meanwhile, unseen inside the engine, PEEK polymer components may be employed in piston ring seals or head gaskets to ensure long-term durability under combustion heat. Together, PTFE and PEEK parts contribute to improved reliability and efficiency in modern vehicles.
Oil & Gas Industry
Few environments are as punishing as oil and gas exploration and production. Downhole tools, wellheads, and refinery equipment face High Pressure High Temperature (HPHT) conditions along with corrosive fluids. This is a field where both PTFE and PEEK have vital roles, but PEEK in particular has become a material of choice for extreme service.
PEEK seals are extensively used in oilfield equipment because they survive where many other materials fail. PEEK can retain its mechanical properties even in pressures beyond 10,000 psi and temperatures above 150°C (302°F). For example, in a wellhead or downhole valve, you might find PEEK seal rings in couplings, wellhead connectors, drill bit assemblies, loading swivels, and blowout preventers. PEEK is also common in ball valve seats, compressor seal rings, pump wear rings, and backup rings in the oil/gas sector. One of the most demanding applications cited is face seals at the wellhead that contain high-pressure production fluids – these often incorporate PEEK because it can handle the combination of high pressure, high temperature, and sour chemicals. PEEK’s advantage here is its ability to resist extrusion and deformation under pressure, ensuring a seal remains tight during pressure spikes. Additionally, PEEK resists attack from crude oil, natural gas (and H₂S or CO₂ in sour gas), and completion fluids, giving it longevity in downhole conditions.
PTFE also has uses in oil and gas, especially in situations demanding top-tier chemical resistance. PTFE backup rings are widely used in O-ring glands for high-pressure tools to prevent elastomer extrusion. PTFE spring-energized seals are used in valves and pumps where chemical compatibility with harsh fluids is critical (for example, in a chemical injection pump or in certain components of subsea equipment). However, pure PTFE would cold-flow under the extreme pressures deep in an oil well, so designs often rely on filled PTFE or PEEK for structural support. It’s not uncommon to see a spring-energized PTFE seal lip combined with a PEEK anti-extrusion ring in high-pressure valves. Where PTFE truly excels in oil/gas is in static seals or gaskets that see aggressive chemicals – for instance, PTFE gasket tape is used on pipe flanges carrying corrosive fluids because it can seal and not be eaten away by acids, amines, or solvents in the process stream. PTFE’s temperature range also covers many oil & gas needs (cryogenic LNG lines up to hot hydrocarbons).
In refinery or petrochemical plants (downstream oil & gas), PTFE gaskets are common for process equipment – they can handle extreme pH chemicals and temperatures up to 260°C in reactors and piping. PEEK, being more expensive, is used more sparingly in downstream plants; you might find it in critical pump components or special valves that see both high mechanical stress and corrosives.
Summing up oil & gas: PEEK has become a workhorse for HPHT seals, downhole tools, and any component where mechanical failure is not an option. It’s used for seals, compressor plates, bearings, and valve seats that face the combined challenges of high pressure, heat, and chemicals. PTFE is invaluable for chemical service seals and gaskets, especially in static applications or as part of composite seal designs, and it’s often utilized for its inertness and low friction in less mechanically demanding roles. Both materials contribute to increased reliability and lifespan of oilfield equipment – preventing leaks in environments where a leaking seal could mean environmental disaster or costly downtime.
Medical Devices & Pharmaceutical/Food Industry
In medical and pharmaceutical applications, material purity and performance under sterilization are paramount. PTFE and PEEK are both used in medical device seals and components, but their roles differ slightly.
PTFE is highly valued in pharmaceuticals and biotech because it is chemically pure and non-reactive. It doesn’t contaminate or leach into fluids, and it can be made in FDA-approved grades. PTFE seals and gaskets are used in pharmaceutical processing equipment, such as pump diaphragms, valve seals, and connectors, where aggressive cleaning chemicals or solvents are present. They ensure no chemical reaction or degradation affects the product purity. PTFE’s smooth, non-stick surface also resists biofilm adhesion, which is helpful for hygiene. In medical devices, PTFE rotary seals can be found in equipment like anesthesia machines, oxygen concentrators, or insulin pumps – anywhere a seal must remain inert and low friction. PTFE is also used as catheter coatings and in surgical instruments for its low friction and biocompatibility. Expanded PTFE (ePTFE) in particular is used for implantable medical devices such as vascular grafts and surgical meshes because it’s biocompatible and porous.
PEEK is one of the few polymers that is biocompatible and suitable for implants. In fact, PEEK is used to make implantable devices like spinal fusion cages, orthopedic pins, and dental implants because it has bone-like modulus and can be sterilized without losing properties. For seals in medical devices, PEEK’s role is often in high-stress components or where repeated sterilization is needed. For example, PEEK washers or seals in surgical hand tools or autoclave equipment can survive hundreds of steam sterilization cycles (at ~134°C) without embrittlement. PEEK’s resistance to gamma radiation also allows it to be used in devices that are sterilized by radiation(it doesn’t become brittle or degrade significantly under high doses of gamma). In drug delivery pumps or certain lab analyzers, PEEK tubing and fittings are common (PEEK tubing is widely used in HPLC machines due to its chemical inertness and pressure capability). This shows PEEK’s chemical resistance is sufficient for most pharmaceutical fluids as well.
For food & beverage processing, both PTFE and PEEK have roles in seals for mixers, valves, and piping. PTFE is often seen in food-grade gasket and seal applications because it’s FDA and EU food-safe, and it doesn’t impart taste or react with food products. PEEK can also be food-grade and may be used in high-temperature food processing equipment (like seals in ovens, fryers, or beverage sterilization units) where metals might corrode.
In summary, PTFE is usually chosen for static or dynamic seals in medical/pharma where chemical inertness and ultra-clean performance are needed – e.g. seals in a chemical reactor for drug synthesis, or a check valve in a medical gas line. PEEK is chosen for parts that need to withstand mechanical load and repeated sterilization – e.g. a surgical instrument bushing, a high-pressure chromatography seal, or even implantable seal components in the body. Both materials have grades meeting FDA and USP Class VI biocompatibility standards, making them go-to high-performance sealing materials in life sciences equipment. The selection often comes down to whether the application is more mechanical (favoring PEEK’s strength) or more chemical/tribological (favoring PTFE’s inert slipperiness).
Industrial Manufacturing & Other Uses
“Industrial manufacturing” covers a broad array of sectors – from chemical processing plants and semiconductor fabrication to heavy equipment and manufacturing machinery. PTFE and PEEK find myriad uses here as well.
In chemical processing and industrial fluid handling, PTFE gaskets and seals are ubiquitous. PTFE sheet gaskets are used on pipe flanges, reactors, and storage tanks because they can withstand aggressive chemicals and high temperatures simultaneously. For example, a PTFE gasket can seal a pipe carrying concentrated acid at 200°C where other gasket materials would degrade – PTFE can handle it with ease. PTFE gasket tape (expanded PTFE) is also used to get a reliable seal on glass-lined steel equipment or irregular flange surfaces, given its adaptability and chemical resistance. Even at 600°F (316°C) and up to 3000 psi, specialized PTFE gasket tapes can maintain a seal. In industrial valves and pumps that handle solvents or corrosives, PTFE O-rings or envelope gaskets (PTFE jacket over elastomer) are common. PTFE’s role here is mainly to ensure no chemical attack or contamination in processes – crucial for product quality and plant safety.
Meanwhile, PEEK is often chosen for mechanical components in industrial machines that need both strength and chemical resistance. For example, in a compressor or pump for a chemical plant, you might find PEEK wear rings, PEEK valve seats, or PEEK bearing cages. PEEK can replace metal in some of these parts to avoid corrosion (a metal might rust or corrode in a chemical environment, whereas PEEK will not). One advantage noted is that PEEK can replace metal wear components while offering excellent resistance to galling and seizing, and it’s self-lubricating so maintenance is reduced. This is why PEEK wear rings show up in high-pressure pumps or mixers – they extend service life without needing constant lubrication.
In the semiconductor manufacturing industry, both materials are used for their purity and performance. PTFE is used for ultrapure water and acid transport lines, wafer handling components, and seals in semiconductor tools because it doesn’t contaminant and can survive the nasty etching chemicals (like HF, which PTFE resists). PEEK, especially carbon-fiber reinforced PEEK, is used in vacuum chamber components, wafer clamp rings, and CMP (chemical mechanical planarization) tool parts where durability and low outgassing are needed. Greene Tweed (a materials supplier) notes that high-purity grades of PTFE are used extensively in fluid handling for semiconductors, whereas PEEK and its variants are used for things like sensor housings and seal components in aircraft engines and other demanding environments
– highlighting the different niches even in industrial contexts.
Heavy equipment and manufacturing machinery: PTFE shows up in things like slide bearings, guide strips, and liners to reduce friction on large machine ways (e.g., Turcite® is a PTFE-based material used on machine tool slides for smooth motion). PEEK shows up in bushings, gear wheels, and wear plates in textile machinery, packaging equipment, etc., where metal replacements are desired to eliminate lubrication and noise. PEEK fasteners (screws, nuts) are even used in chemical plants and high-temperature ovens where metal fasteners might seize or corrode – PEEK fasteners can handle the heat and are non-corroding.
Summing up industrial uses: If the application is a chemical-resistant gasket or seal for a tank, pipe, or industrial valve, PTFE is usually the top choice due to its near-universal chemical compatibility and temperature range. If the application is a structural or wear component in equipment that also faces heat/chemicals, PEEK is often the go-to, since it provides metal-like strength with polymer corrosion resistance. Many industrial sealing solutions marry the two: for instance, a mechanical seal in a pump may use a PTFE sealing face for low friction against a rotating shaft, combined with a PEEK retainer or jacket for support. Both materials help plants achieve longer maintenance intervals and solve challenging sealing problems that would confound more ordinary plastics or rubbers.
Material Selection Guide: Choosing PTFE vs PEEK for Your Seals
Selecting between PTFE and PEEK for a seal or gasket comes down to balancing your application’s requirements in several key areas. Here’s a practical selection guide for engineers and procurement teams to decide the right material:
- Chemical Environment: What media will the seal contact? If you are sealing against extremely corrosive chemicals or a wide range of reagents, PTFE is usually the safer choice due to its virtual inertness. PTFE gaskets are ideal for acid, caustic, solvent, and reactive gas pipelines – they’ll stay unscathed where other plastics might fail. PEEK also handles most chemicals, but check for specific incompatibilities (like concentrated acids). For instance, if the process involves concentrated sulfuric acid or nitric acid at high temperature, PEEK would be a poor choice (risk of degradation). On the other hand, in oil & gas fluids, fuels, or water/steam service, PEEK does fine. Verdict: Use PTFE for the most chemical-resistant gaskets and seals in harsh chemical processing. Use PEEK if chemicals are moderate and other factors below push toward PEEK.
- Temperature Range: What temperatures will the seal see (both continuous and peaks)? Both materials handle up to ~250°C in continuous operation, but PEEK retains its mechanical strength better near that high end. If your seal will see sustained temperatures above ~230°C while under load (e.g., a pressurized steam seal or an engine exhaust seal), PEEK is more likely to maintain a tight seal without deforming. PEEK can also handle short excursions to 300°C+. Conversely, for cryogenic temperatures or very rapid temperature cycling, PTFE’s flexibility can be advantageous (it won’t crack with thermal shock). Also consider the temperature plus chemicals together: PTFE can handle hot, strong acids that PEEK cannot. Verdict: For extremely high-heat applications (250°C and up, or >200°C with high pressure), lean towards PEEK. For sub-zero or broad-range applications (e.g., -100°C to +200°C) and purely thermal compatibility, PTFE usually suffices.
- Mechanical Load & Pressure: Will the seal face high pressure or mechanical stress? This is a critical differentiator. Under high loads, PEEK outperforms PTFE – it has much higher load-bearing capacity and resists creep . If the seal is in a high-pressure valve (hundreds of bar) or under heavy bolt load (as in a torque-tightened gasket), PEEK will maintain shape and seal integrity better over time. PTFE, if used, might need a design compensation (like a thicker section or a spiral wound gasket form) to avoid creep. For example, at 20,000 psi downhole tools, PEEK seal rings are standard, whereas PTFE would extrude unless backed by a retainer. Verdict: For high-pressure systems, large mechanical loads, or vacuum seals needing dimensional stability, choose PEEK or ensure PTFE is heavily reinforced. For low to medium pressure (say <50 bar) and when other factors favor PTFE, PTFE can be used and is easier to conform into the seal cavity.
- Dynamic vs Static Sealing: Is the application dynamic (moving parts) or static? Dynamic seals (rotary or reciprocating) often benefit from PTFE because of its low friction and ability to run without lubrication. A PTFE lip seal on a shaft will generate less heat and last longer without lubrication than a PEEK seal would (PEEK might cause more friction and wear on the mating shaft). PTFE also handles slight misalignments or eccentric motion well by deforming to maintain contact (especially with an energizer spring). Static seals (gaskets, face seals) that just sit in one place under compression can use either material, but if the static seal has to also support loads or pressure, PEEK’s stiffness can be a benefit (e.g., PEEK anti-extrusion rings in a static O-ring groove). Verdict: For dynamic, sliding applications (valve stem seals, shaft seals, guide rings) where friction is critical, PTFE is usually preferred (sometimes PTFE blended with carbon or bronze for a bit more wear resistance). For static seals under high stress or where extrusion is a risk, consider PEEK for structural support or as the seal itself.
- Wear and Longevity: Does the seal need to last a particularly long time or through abrasive conditions? If you need a seal or wear ring that lasts for many years in service or sees abrasive media, PEEK offers outstanding wear and fatigue resistance . It’s often chosen for long-life applications (10+ year service) because it will hold up physically. PTFE can wear faster, especially unfilled, but in gentle conditions it can also last a long time. PEEK’s hardness also means it’s less likely to get nicked or damaged during handling and installation – PTFE being softer can be scratched or cold-flow if mishandled. Verdict: For maximum durability and wear resistance, especially in a harsh mechanical environment, choose PEEK (or a filled PTFE if cost is a concern and chemistry allows). For lighter-duty or low-friction critical applications, PTFE’s adequate durability and lower friction may suffice.
- Regulatory and Purity Requirements: Are there FDA, USDA, or other regulatory requirements? Must the material be ultra-pure? Both PTFE and PEEK can be formulated to meet FDA and other standards (virgin PTFE is FDA compliant, and certain grades of PEEK like medical-grade or food-grade PEEK are available). However, PTFE has a longer track record in food/pharma as a gasket material (it’s easier to get PTFE that’s compliant and it’s inherently non-toxic and non-additive). PEEK is used too, but make sure to specify FDA-grade PEEK if it’s contact with ingestibles. For semiconductor or vacuum, note that PTFE outgasses extremely little and has no moisture absorption, whereas PEEK has low but not zero moisture uptake (which could matter in ultra-high vacuum). Verdict: Both can be used in clean/regulated environments, but PTFE is often the default for food/pharma gaskets due to its inert history. Use whichever meets the specific certifications needed; otherwise base the choice on performance.
- Cost Constraints: Is cost a major factor or is performance paramount? As noted, PEEK is much more expensive than PTFE. If you’re designing a high-volume product and can possibly get away with PTFE, the cost savings will be significant. PTFE is also more widely available off-the-shelf in various standard gasket and seal forms, which can reduce lead times and cost. PEEK tends to be used in mission-critical or high-value equipment where the cost is justified by the performance (for example, in a jet engine or downhole drilling tool, the cost of material is minor compared to the system cost; but in a simple pipeline flange, PEEK would be overkill). Verdict: Use PTFE whenever it meets the requirements, as it is more economical and readily available. Only specify PEEK when the operating conditions (temperature, pressure, load, etc.) exceed PTFE’s capabilities or when a failure of a PTFE part would be catastrophic enough to warrant the extra expense of PEEK.
- Combination Solutions: It’s not always an either-or choice. In some cases, the best solution is a hybrid: for example, a seal assembly where PTFE is used as the sealing interface and PEEK is used as a support ring or adapter. As mentioned earlier, head gaskets combining PEEK and PTFE have shown great promise in automotive engines – leveraging PEEK’s heat resistance and PTFE’s surface conformability. Spring-energized seals often use PTFE for the jacket and a metal spring for resilience, but in high-temp cases the jacket could be PEEK, or a PTFE jacket could be backed by a PEEK cap. Don’t be afraid to use both materials together to exploit the best attributes of each.
By considering these factors – chemicals, temperature, pressure, motion, regulatory needs, and cost – you can arrive at a material choice that best fits your application. In summary, choose PTFE seals for broad chemical compatibility, low friction, and economy, and choose PEEK seals for high stress, high temperature, and demanding mechanical durability. If still in doubt, consult with seal manufacturers or material specialists who can offer guidance (and even testing) for your specific scenario.
Frequently Asked Questions (FAQ) about PTFE and PEEK Seals
Q1: Which material handles higher temperatures, PTFE or PEEK?
A1: Both can handle up to 250°C (482°F) continuously, but PEEK can handle higher temperatures under load than PTFE. PEEK parts remain strong and won’t deform even at 300°C in high-pressure conditions. PTFE can survive up to ~260°C, but at that extreme a PTFE seal under pressure will tend to creep or lose shape. So for sustained high-heat (250°C+) especially with stress, PEEK is better. PTFE is fine up to 260°C in lower stress settings and actually performs better at cryogenic lows.
Q2: Is PEEK more durable than PTFE?
A2: In terms of mechanical durability and load-bearing, yes, PEEK is generally more durable. It has higher tensile strength and hardness, so it’s less prone to wear or deformation under stress. PEEK seals often outlast PTFE seals in high-pressure or high-speed wear applications. However, durability also depends on conditions: PTFE is extremely durable against chemical attack (it won’t degrade in corrosive environments that might eventually age other plastics). PTFE also has a kind of “fatigue resistance” in flexing applications because of its flexibility. But if we’re talking overall lifespan in a demanding mechanical application, PEEK’s resistance to creep and wear means it usually has a longer service life than PTFE in the same application.
Q3: What are the chemical limitations of PTFE and PEEK?
A3: PTFE is almost universally chemical resistant – it can handle strong acids, bases, solvents, chlorine, you name it. The rare chemicals that attack PTFE include fluorine gas (especially at high temp), high-temperature oxygen plasma, molten alkali metals, and certain highly reactive fluorinated compounds. These are not common in most industrial processes. PEEK is also very chemically resistant, but it does have a weakness to concentrated acids and some halogens. For example, concentrated sulfuric acid will quickly attack PEEK, and PEEK is not good with nitric acid or bromine at high temps. In most oil/gas, water, hydrocarbon, or mild chemical environments, PEEK is fine. In summary: use PTFE for extremely aggressive chemistries (it’s the safer bet), and avoid PEEK with strong acids/oxidizers – check a compatibility chart if in doubt.
Q4: Can PTFE and PEEK seals be used together?
A4: Absolutely. In fact, many advanced sealing systems combine the two to get the best performance. For example, a cylinder head gasket was developed using a composite of PEEK and PTFE to exploit PEEK’s heat resistance and PTFE’s sealing qualities. Another common pairing is using a PTFE sealing lip with a PEEK anti-extrusion or backup ring in high-pressure hydraulic seals. You might also see PEEK valve seats with a PTFE coating to reduce friction. Using them together is a smart way to handle complex requirements – there’s no chemical incompatibility between PTFE and PEEK, so they won’t react adversely. Just be mindful that combining them can add cost (due to PEEK content) and complexity.
Q5: What’s the difference between PTFE and Teflon?
A5: None in terms of material – Teflon™ is the brand name for PTFE resin made by Chemours (formerly DuPont). It has become a generic trademark often used to refer to PTFE, but technically PTFE is the polymer’s name. So a Teflon seal is a PTFE seal. Just ensure when specifying that you get virgin PTFE vs. mechanical grade or filled, depending on your needs.
Q6: Are PTFE and PEEK seals FDA approved / food safe?
A6: They can be. Virgin PTFE (unfilled PTFE) is generally considered safe for food and pharma use and is FDA compliant. It’s often used in food processing equipment and medical devices for this reason. PEEK can also be made in food-grade or medical-grade versions (for example, Victrex PEEK has grades that meet FDA and EU food contact regulations, and PEEK is USP Class VI biocompatible for medical implants). If you need a food-safe seal, specify “FDA-compliant PTFE” or “food-grade PEEK.” Both materials are basically inert and don’t shed harmful chemicals, but using certified grades ensures no additives or fillers that aren’t approved.
Q7: Why is PEEK so much more expensive than PTFE?
A7: PEEK is expensive for a few reasons: (1) It’s produced in much lower volume globally than PTFE, making it a specialty polymer. (2) Its manufacturing process and raw materials are more complex and costly. (3) PEEK is often sold into high-tech industries that are willing to pay a premium for its performance, which keeps the price high. By contrast, PTFE, while not cheap, has been around longer (discovered in 1938 vs. PEEK in late 1970s) and is made by many suppliers in large quantities, which lowers its cost somewhat. Roughly, PEEK can cost on the order of 5-10 times more per kilogram than PTFE. For procurement, this means PEEK seals will significantly impact your material budget. Always verify that the added performance of PEEK is truly needed. In some cases, a filled PTFE or another polymer might suffice at a lower cost. But for those cases where only PEEK works, its cost is justified by avoiding failure in service.
Q8: Do I need special handling or installation procedures for PTFE or PEEK seals?
A8: Generally, they don’t require much special treatment beyond what you’d do for any high-quality seal. A few pointers: PTFE is more pliable and can be easily nicked or scratched, so handle virgin PTFE parts carefully to avoid gouging the sealing surfaces. It also can be slightly less elastic – PTFE O-rings, for example, come as “solid” rings that you might need to gently heat or use a two-piece design to install (since they don’t stretch like rubber). PEEK is very hard, so ensure mating surfaces are smooth; a rough metal shaft can quickly abrade a PEEK seal. Both materials are hydrophobic, so unlike rubber seals, there’s no need to grease them for moisture – but a light lubricant can help with assembly to prevent any galling (especially for PEEK in contact with metal). If a PTFE seal is energized by a spring, be careful not to deform the spring during installation. And importantly, perform a safety de-rating for pressure with PTFE seals at high temperature (as some manufacturers advise) – meaning don’t assume the same pressure rating at 20°C applies at 200°C due to PTFE’s creep.
By understanding these FAQs and the earlier comparisons, you should be well-equipped to choose between PTFE and PEEK for your sealing needs. Both materials are champions of the sealing world – the key is aligning their strengths with your application’s demands to achieve a reliable, long-lasting seal.
Conclusion
Both PTFE and PEEK seals have their unique advantages. PTFE is unbeatable for chemical resistance and low friction, while PEEK excels in strength, wear resistance, and high-pressure applications. Choosing the right material depends on the specific needs of your application. If you’re still unsure, feel free to contact us at FLUIDMEC for expert advice!
