Rotary Shaft Seal Materials: PTFE, Nitrile, Silicone Compared
How to choose the best material for rotary shaft seals
Why material selection matters for rotary shaft seals
Rotary shaft seals are critical components in hydraulic, pneumatic and rotating machinery applications. Choosing the right seal material determines leak prevention, service life, energy loss (through friction), and maintenance intervals. Engineers evaluate temperature limits, chemical compatibility, abrasion and wear resistance, dynamic friction, hardness, extrusion resistance and cost. This guide compares three commonly used materials—PTFE (polytetrafluoroethylene), Nitrile (NBR) and Silicone—so you can select the best option for your rotary shaft seals.
Overview of PTFE, Nitrile (NBR) and Silicone for rotary shaft seals
Material fundamentals and common uses for rotary shaft seals
PTFE: A low-friction, chemically inert fluoropolymer widely used where low friction, wide temperature range and aggressive chemical resistance are required. PTFE versions may be filled (carbon, bronze, glass, MoS₂) to improve wear, stiffness and sealing performance.
Nitrile (NBR): A petroleum-based synthetic rubber with strong oil and fuel resistance, good mechanical properties and low cost. It is the most common elastomer for oil seals and many rotary shaft seals in hydraulic and automotive applications.
Silicone: A silicon-oxygen polymer with excellent high/low temperature performance and flexibility. Silicone rubber offers wide temperature capability and good non-reactivity, but lower abrasion resistance and tensile strength than NBR.
Direct comparison: PTFE vs Nitrile vs Silicone for rotary shaft seals
Key performance metrics engineers search for
| Property | PTFE | Nitrile (NBR) | Silicone |
|---|---|---|---|
| Typical temp. range | -200°C to +260°C (continuous varies with filler) | -40°C to +120°C (high-temp NBR up to ~150°C briefly) | -60°C to +200°C (depends on formulation) |
| Dynamic friction | Very low (ideal for high-speed rotary seals) | Moderate (good for most rotary oil seals) | Low to moderate (can cause stick-slip at low speed) |
| Wear/abrasion resistance | Good when filled; virgin PTFE can cold flow | Good abrasion resistance; elastomeric recovery helps | Poor to fair (not ideal for abrasive media) |
| Chemical resistance | Excellent to most chemicals and solvents | Good to petroleum oils, fuels, many hydraulic fluids | Good to polar solvents, water; poor to fuels/oils |
| Compression set | Low (PTFE maintains shape; but rigid) | Moderate (varies with durometer and temp) | Higher (silicone can take set under long static load) |
| Extrusion resistance | High (rigid designs or backup rings often still needed) | Moderate (requires backup rings at high pressure/high gaps) | Poor to moderate (soft material, needs support in high pressure) |
| Typical applications | High-speed rotary seals, chemical industry, food/pharma | Hydraulic shaft seals, gearboxes, automotive oil seals | Temperature-critical systems, food, medical devices (non-lubricated) |
| Relative cost | High | Low to moderate | Moderate to high (depending on grade) |
Sources for typical ranges: manufacturer datasheets and seal handbooks listed in References.
How temperature and media decide material for rotary shaft seals
Application-driven selection rules
Temperature: If continuous service will approach or exceed ~120°C, NBR often becomes unsuitable—consider PTFE or silicone. For cryogenic or very low-temperature seals (<-40°C) PTFE or silicone are better choices than standard NBR.
Chemical compatibility: For aggressive solvents, acids, bases or cleaning agents, PTFE is often a safe default because of its broad chemical inertness. For oil-based hydraulic systems and fuels, NBR is generally preferred because of oil swell compatibility and proven resistance.
Dynamic performance: speed, shaft finish, pressure and friction for rotary shaft seals
Matching material to kinematic and geometric constraints
Surface speed: PTFE’s low friction is advantageous at high surface speeds to reduce heat and wear. For moderate speeds and pressures commonly found in hydraulic and automotive rotary seals, properly compounded NBR with optimized lip geometry provides reliable sealing.
Shaft finish and hardness: Elastomers like NBR rely on a conforming lip and surface contact; rough shafts accelerate wear. Recommended shaft finish and hardness depend on material—PTFE tolerates slightly rougher surfaces if filled and backed with appropriate design.
Design strategies: when to use filled PTFE, FKM blends or special NBRs for rotary shaft seals
Engineering trade-offs and common customizations
Filled PTFE: Adding bronze, carbon or glass fillers increases wear resistance, reduces cold flow and improves thermal conductivity. For rotary seals in high-speed pumps or aggressive chemicals, filled PTFE often outperforms elastomers despite higher cost.
NBR variants: Hydrogenated NBR (HNBR) offers better high-temperature and oxidative resistance; specialty nitriles improve low-temp flexibility or fuel resistance. Select the specific compound based on fluid compatibility charts and operating temperature ranges.
Silicone formulations: Useful when flexibility across a wide temperature band is required, or for non-oil, clean environments (medical, food). Silicone’s lower abrasion resistance often requires protective design features or sacrificial lips.
Cost vs life-cycle: ROI considerations for rotary shaft seals
Balancing up-front cost with maintenance and downtime
PTFE seals cost more but can reduce downtime and energy consumption in high-speed or chemically aggressive systems, often yielding lower life-cycle costs. NBR is cost-effective for standard hydraulic and automotive applications where fluids and temperatures are within its capability. Silicone is cost-efficient for temperature-critical, low-wear applications.
Practical selection checklist for engineers specifying rotary shaft seals
Step-by-step decision flow you can use
- 1) Record operating temperature range and peak temperatures.
- 2) Identify fluids, solvents and contaminants the seal will contact.
- 3) Determine shaft speed (m/s), pressure and shaft finish.
- 4) Evaluate required lifetime, maintenance access and downtime cost.
- 5) Choose candidate materials (PTFE, NBR, Silicone, or specialty blends) and consult supplier compatibility charts.
- 6) Prototype and test on a bench for friction, wear, and leak under real conditions.
Polypac: technical partner for custom rotary shaft seals and materials
Why choose Polypac for rotary shaft seals and sealing materials
Polypac is a scientific and technical hydraulic seal manufacturer and oil seal supplier specializing in seal production, sealing material development, and customized sealing solutions for special working conditions. Founded in 2008, Polypac began with filled PTFE seals (bronze, carbon, graphite, MoS₂, glass) and has expanded to O-rings and elastomer seals across NBR, FKM, silicone, EPDM and FFKM.
Facility and capabilities: Polypac's custom rubber ring and O-ring factory covers more than 10,000 m², with 8,000 m² of factory space. Production and testing equipment rank among the industry’s most advanced. Long-term collaborations with universities and research institutions support material development and testing, enabling tailored solutions for rotary shaft seals operating under high temperature, high speed, abrasive or chemically aggressive conditions.
Main products and advantages: Polypac manufactures O-Rings, Rod Seals, Piston Seals, End Face Spring Seals, Scraper Seals, Rotary Seals, Back-up Rings and Dust Rings. The company’s strengths include:
- Expertise in filled PTFE manufacturing and a broad material portfolio.
- Custom compound development and rapid prototyping for special environments.
- Advanced production and testing facilities to ensure consistent quality.
- Large-scale capacity with industry partnerships for applied R&D.
If your rotary shaft seal needs a bespoke material grade, a filled PTFE design for high-speed service, or a specialty elastomer for hydraulic oil compatibility, Polypac can develop and produce optimized solutions to reduce leakage and increase component life.
Comparison data and recommended use cases for rotary shaft seals
Quick-reference recommendation table
| Material | Best when | Not recommended when |
|---|---|---|
| PTFE (filled) | High-speed rotary shafts; aggressive chemicals; wide temp. ranges | Low-cost, low-speed oil-only systems where elastomer lip sealing is adequate |
| NBR (standard) | Hydraulic oil seals; automotive; general-purpose rotary seals | High-temp (>120°C) or strong solvents that attack nitrile |
| Silicone | Extreme temperature swings; low-temp flexibility; medical/food (non-oil) | Abrasive environments or oil/fuel-heavy systems without special formulation |
Testing and verification: what to request from your seal supplier
Essential test certificates and trial steps
Ask for:
- Material datasheets (temperature, hardness, chemical compatibility).
- Dynamic leakage test results at representative speed, pressure and temperature.
- Wear and abrasion test reports or field performance case studies.
- Sample parts for bench testing and a short field trial period.
Polypac provides production test data and can support application-specific testing through partner labs and academic collaborators.
Frequently Asked Questions (FAQ) about rotary shaft seals
1. Which material is best for high-speed rotary shaft seals?
Filled PTFE is typically best for high speeds due to its low friction and thermal resistance. Proper filler choice (e.g., carbon or MoS₂) improves wear resistance. Validate with bench tests at expected rpm and surface speed.
2. Can Nitrile (NBR) be used for hydraulic rotary shaft seals?
Yes. NBR is the standard choice for many hydraulic systems because of its compatibility with petroleum-based oils and fuels. For higher temperatures or oxidative environments, consider HNBR or alternative elastomers.
3. Is silicone suitable for oil-lubricated rotary seals?
Generally no—silicone has poor resistance to many hydrocarbon oils and can swell. It is favored for temperature extremes, food and medical applications, or where non-oil liquids are involved.
4. When should I choose a filled PTFE seal over an elastomeric one?
Choose filled PTFE when you need low friction at high speed, exceptional chemical resistance, wide temperature range, or when elastomer wear limits service life. Consider cost and the need for correctial design (back-up rings, housings) to avoid cold flow/extrusion.
5. What design features reduce extrusion risk in high-pressure rotary seals?
Use back-up rings, choose stiffer materials (filled PTFE), reduce clearance gaps, and select lip geometry optimized for pressure. Proper material hardness and reinforcement can greatly reduce extrusion.
6. How do I verify a material’s compatibility with my fluid?
Request chemical compatibility charts and material datasheets from the supplier, and perform soaking and dynamic leakage tests under expected temperature/pressure conditions. If uncertain, Polypac can help run application-specific tests.
Contact and next steps — get custom rotary shaft seals
Talk to Polypac for specification, samples and testing
If you need help selecting the best material or designing rotary shaft seals for challenging conditions, contact Polypac for technical consultation, custom compound development and prototype seals. Our capabilities include filled PTFE designs, a wide elastomer portfolio (NBR, FKM, silicone, EPDM, FFKM), and production/testing at scale.
Request a quote, samples, or application review to reduce leakage risk and extend seal life.
References
- DuPont: Teflon (PTFE) properties overview. https://www.dupont.com/products/teflon-polytetrafluoroethylene-ptfe. (accessed 2025-11-01).
- Parker O-Ring Handbook and material compatibility guides. https://www.parker.com (O-Ring Handbook) (accessed 2025-10-28).
- Trelleborg Sealing Solutions: Elastomer material guides and temperature ranges. https://www.trelleborg.com/en/seals (accessed 2025-10-30).
- SKF: Shaft sealing solutions — design considerations for rotary seals. https://www.skf.com (accessed 2025-09-15).
- MatWeb Material Property Data: PTFE, NBR, Silicone typical properties. https://www.matweb.com (accessed 2025-10-20).
For technical consultation or to request samples and production quotes, contact Polypac through the company's sales channels or visit the Polypac product catalog for O-Rings, Rod Seals, Piston Seals, End Face Spring Seals, Scraper Seals, Rotary Seals, Back-up Rings and Dust Rings.
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