Polytetrafluoroethylene, or PTFE, is a synthetic fluoropolymer best known by its brand name, Teflon. This remarkable material was accidentally discovered in 1938 and has since become a staple in countless industrial and consumer applications. What sets PTFE apart is its combination of chemical resistance, thermal stability, electrical insulation, and—perhaps most notably—its extremely low friction coefficient.
The PTFE friction profile makes it an ideal choice in situations where materials must slide smoothly without sticking or generating heat. Whether it’s a bearing inside a motor, a sliding valve in a chemical plant, or a coating on a frying pan, PTFE’s low friction capabilities shine across a wide range of uses.
This article explores in depth the coefficient of friction for PTFE, why it’s considered the benchmark for low-friction materials, how it compares to alternatives, and what you need to know when specifying PTFE in your applications.
What Is Friction Coefficient and Why It Matters
To fully appreciate PTFE’s low friction properties, it’s important to understand the concept of friction coefficient, often abbreviated as COF.
Understanding the Coefficient of Friction (COF)
The coefficient of friction is a numerical value that represents the resistance between two surfaces sliding against each other. It’s a dimensionless number, typically ranging between 0 (no friction) and 1 (high friction), although some materials can exceed 1 in very sticky scenarios. The lower the value, the smoother the interaction between surfaces.
There are two types of friction coefficients:
- Static friction coefficient: The force required to start moving one object over another.
- Dynamic (or kinetic) friction coefficient: The force required to keep the object moving.
When discussing PTFE friction, the focus is usually on dynamic friction since PTFE is commonly used in components that are in continuous motion.
Why the COF Matters in Engineering and Design
The coefficient of friction has real-world implications in mechanical performance, energy efficiency, and system longevity. For example:
- A low COF reduces wear between two contacting parts, extending their lifespan.
- It minimizes the energy needed to maintain motion, which is crucial in motors, conveyors, and bearings.
- Lower friction means less heat generation, reducing the risk of thermal degradation.
PTFE’s Friction Coefficient: How Low Can It Go?
When it comes to low friction materials, PTFE is the undisputed champion. In fact, it holds one of the lowest coefficients of friction among all solid materials, making it a go-to choice for engineers aiming to minimize resistance between moving parts.
Typical Friction Coefficient Values for PTFE
- Static COF: ~0.05–0.10
- Dynamic COF: ~0.04–0.08
These values can vary slightly depending on specific conditions (load, surface finish, speed, temperature), but PTFE’s COF is consistently low across the board. This ultra-smooth performance makes PTFE ideal for sliding applications with minimal wear and drag.
PTFE vs. Other Common Materials
Let’s look at how PTFE compares with other materials in terms of dynamic friction coefficients:
| Material | Approx. COF (Dynamic) |
|---|---|
| PTFE (Teflon) | 0.04 – 0.08 |
| Nylon | 0.20 – 0.30 |
| UHMW-PE | 0.10 – 0.20 |
| Acetal (POM) | 0.15 – 0.25 |
| Stainless Steel | 0.50 – 0.60 |
| Rubber | 0.80 – 1.00 |
This stark contrast shows just how unique PTFE’s friction performance really is. Even other “low friction” plastics like UHMW and Nylon can’t match it.
Why PTFE’s Low Friction Matters
- Smooth motion: Reduces stick-slip behavior in precision applications.
- Lower wear: Protects mating surfaces and components.
- Energy savings: Less resistance means motors work less and last longer.
- Versatility: Maintains low COF across wide temperature and pressure ranges.
Engineers and designers in industries such as aerospace, electronics, medical, and heavy machinery often rely on low friction PTFE to ensure high-performance and maintenance-free operation.
Factors Influencing PTFE Friction
While PTFE’s friction coefficient is naturally low, real-world conditions can influence how it performs in a given application. Understanding these factors helps engineers fine-tune system performance and choose the right PTFE grade or form for their needs.
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Surface Roughness and Finish
PTFE performs best when paired with smooth, polished surfaces. Rougher surfaces may increase the contact area and lead to a slightly higher PTFE friction value. However, PTFE can conform slightly to surface irregularities, helping maintain low friction even under suboptimal conditions. -
Pressure and Load
PTFE exhibits a unique friction behavior under pressure. Unlike many other materials, the coefficient of friction for PTFE often decreases with increasing pressure—up to a certain limit. This “pressure-velocity” (PV) relationship makes PTFE suitable for high-load applications like bearings and seals. -
Temperature
PTFE operates effectively across a wide thermal range (around -200°C to +260°C). Its friction coefficient remains relatively stable across these temperatures. However, extremely high temperatures close to the upper limit may soften the material, especially in dynamic applications, potentially affecting long-term performance. -
Speed and Motion Type
- Lower speeds can lead to slightly higher static friction (stick-slip behavior).
- Higher speeds promote a more stable dynamic COF, where PTFE truly shines.
- PTFE performs better in sliding motion than in rolling or oscillating contacts.
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Presence of Lubricants
PTFE is often called a “self-lubricating” material because of its low surface energy and resistance to adhesion. In high-friction or abrasive environments, external lubricants can further reduce wear without significantly changing the already low PTFE friction coefficient.
Applications Benefiting from Low Friction PTFE
Thanks to its exceptionally low coefficient of friction, PTFE is widely used in industries where reducing drag, wear, and energy consumption is critical. Its performance under pressure, temperature, and motion makes it a go-to material for countless engineering challenges.
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Bearings and Bushings
PTFE bushings and plain bearings are popular in machinery where lubrication is difficult or undesirable. These components run quietly and efficiently, even in dry environments, due to PTFE’s low friction surface.Benefits: Extended life, no need for greasing, low noise
Use Cases: Automotive suspension systems, conveyor rollers, food processing machines -
Seals and Gaskets
Sealing components made from PTFE maintain tight tolerances while allowing for smooth movement between parts. The low friction PTFE material ensures less wear and a better seal over time.Benefits: Chemical resistance + reduced drag
Use Cases: Hydraulic systems, pumps, chemical handling equipment -
Sliding Pads and Wear Strips
PTFE is often applied as sliding pads, liners, or wear strips in mechanical assemblies where consistent motion and minimal friction are required. These strips reduce stress on metal parts and extend service life.Benefits: Minimized surface damage, silent motion
Use Cases: Elevators, bridge expansion joints, industrial robots -
Cable and Wire Insulation
In electrical and communication systems, PTFE-coated wires benefit from both its thermal resistance and smooth, low-friction outer surface, making them easier to route through tight channels or moving joints.Benefits: Ease of installation, high dielectric strength
Use Cases: Aerospace wiring, medical equipment, RF cables -
Valves and Stem Packing
In valves, PTFE stem packing ensures smooth actuation and reliable sealing without binding, especially in aggressive chemical environments. The friction coefficient for PTFE allows consistent torque even after long idle periods.Benefits: Low torque operation, excellent corrosion resistance
Use Cases: Oil & gas valves, pharmaceutical process equipment -
Medical and Laboratory Equipment
PTFE’s inertness and low surface energy allow for hygienic and frictionless movement in delicate instruments. Syringes, slide bearings, and lab automation gear often use low friction PTFE parts.
Enhancing PTFE’s Friction Properties with Fillers
While virgin PTFE already boasts one of the lowest friction coefficients among engineering materials, certain applications demand even more customized performance. That’s where filled PTFE comes in—engineered composites designed to improve wear resistance, reduce creep, and optimize PTFE friction behavior.
Why Add Fillers to PTFE?
Fillers are introduced to:
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Enhance mechanical strength
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Improve thermal conductivity
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Boost wear resistance
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Modify frictional behavior for specific applications
Although adding fillers may slightly increase the coefficient of friction for PTFE, they significantly improve dimensional stability and long-term performance under load.
Common PTFE Fillers and Their Effects
| Filler Type | Effect on PTFE Friction | Typical Applications |
|---|---|---|
| Glass Fiber | Slightly increases COF; improves wear and compressive strength | Bearings, seals, piston rings |
| Carbon | Balances low friction with increased conductivity and hardness | Valves, dynamic seals, pumps |
| Graphite | Maintains low friction under load; excellent in dry lubrication | Sliding components, thrust washers |
| Bronze | Adds wear resistance and thermal conductivity; raises COF | High-speed rotating parts |
| Molybdenum Disulfide (MoS₂) | Lowers friction under load; excellent in high PV conditions | Gears, bushings, heavy-duty equipment |
Trade-Off: Friction vs. Wear Resistance
In some designs, a slightly higher PTFE friction coefficient may be acceptable if it results in dramatically lower wear and longer service life. Engineers must weigh these trade-offs based on:
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Load and speed conditions
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Temperature environment
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Contact surface material
Filled PTFE grades allow tailored performance, making them essential in high-demand applications such as aerospace actuators, industrial valves, and compressor rings.
PTFE vs Other Low Friction Plastics – How It Compares
While PTFE is often the first material that comes to mind when discussing low friction plastics, several other engineering polymers also offer favorable sliding characteristics. However, PTFE continues to stand out due to its exceptionally low coefficient of friction, chemical resistance, and thermal stability.
PTFE vs UHMW-PE (Ultra-High Molecular Weight Polyethylene)
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Friction Coefficient: UHMW-PE typically ranges from 0.10 to 0.20, which is higher than PTFE (0.04–0.08).
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Wear Resistance: UHMW-PE often outperforms PTFE in abrasive environments due to its superior toughness.
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Cost: UHMW is generally more cost-effective.
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Applications: UHMW is common in bulk material handling and food processing.
PTFE wins in friction performance; UHMW wins in abrasion resistance.
PTFE vs Acetal (POM)
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Friction Coefficient: Acetal’s COF is around 0.15–0.25, much higher than PTFE.
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Dimensional Stability: Acetal offers excellent stiffness and machinability.
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Chemical Resistance: PTFE is far superior.
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Applications: Gears, automotive parts, electrical insulators.
PTFE excels in low-friction and chemical resistance; Acetal is better where rigidity and precision are key.
PTFE vs Nylon
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Friction Coefficient: Nylon ranges from 0.20–0.30, much higher than PTFE.
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Moisture Sensitivity: Nylon absorbs water, affecting its stability—unlike PTFE.
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Strength: Nylon is stronger under mechanical load.
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Applications: Wear pads, bushings, pulleys.
PTFE provides better friction performance and stability; Nylon may be stronger structurally but less reliable in wet or chemically harsh environments.
Summary Table: PTFE vs Other Plastics
| Property | PTFE | UHMW-PE | Acetal (POM) | Nylon |
|---|---|---|---|---|
| Friction Coefficient | 0.04–0.08 | 0.10–0.20 | 0.15–0.25 | 0.20–0.30 |
| Chemical Resistance | Excellent | Good | Moderate | Poor |
| Temperature Resistance | -200°C to +260°C | Up to 80°C | Up to 120°C | Up to 100°C |
| Water Absorption | None | Very Low | Low | High |
| Machinability | Good | Fair | Excellent | Good |
PTFE’s unbeatable low friction performance makes it the top choice in high-precision and chemically aggressive applications—even if it’s not the strongest or toughest plastic in the toolbox.
Testing and Measuring PTFE Friction Coefficient
Understanding and quantifying the coefficient of friction for PTFE is essential for engineers designing precision systems. Laboratory testing ensures that PTFE materials meet friction, wear, and load expectations under real-world conditions.
What Is Coefficient of Friction (COF)?
The coefficient of friction is a dimensionless number that measures the resistance to sliding between two surfaces. It is typically categorized into:
- Static COF: Resistance to starting movement
- Dynamic (Kinetic) COF: Resistance during continuous motion
For PTFE, both values are among the lowest of any known solid:
- Static COF: ~0.05–0.10
- Dynamic COF: ~0.04–0.08
Standard Test Methods
Several standardized tests are used to determine the PTFE friction coefficient accurately:
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ASTM D1894 – Standard Test Method for Static and Kinetic COF of Plastics
This is the most common method. A weighted sled with PTFE slides over a test surface at a specified speed while measuring resistance.Output: Static and kinetic COF
Conditions: Ambient temperature and humidity-controlled -
ASTM D3702 – Wear Rate and Friction Coefficient in Thrust Washer Applications
This test is used for PTFE in dynamic applications like bearings and seals. It simulates rotary or oscillating motion under load.Output: COF and wear factor (k)
Commonly used for: Filled PTFE grades -
Pin-on-Disk Testing
A pin made of one material (e.g., PTFE) rotates or slides against a disk of another material under controlled load and speed.Output: COF and wear track analysis
Useful for: Simulating real sliding contact behavior
Factors Affecting COF Measurements
The friction performance of PTFE depends on test conditions, such as:
- Load and pressure
- Sliding speed
- Surface roughness of mating material
- Temperature and humidity
- Presence of lubricants or contaminants
Tips for Using PTFE in Low Friction Applications
To get the most out of PTFE in various applications, proper design and handling strategies are essential:
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Choose the Right PTFE Grade for the Job
- Virgin PTFE: Best for chemically aggressive or clean environments; lowest friction, but less wear resistance.
- Filled PTFE (e.g., glass, carbon, graphite): Slightly higher friction but offers better wear life and mechanical strength—ideal for high-load, high-wear conditions.
Pro tip: Use virgin PTFE when minimizing friction is critical; choose the appropriate filler for durability. -
Mind the Surface Finish of Mating Materials
The surface roughness of the material in contact with PTFE greatly affects the overall coefficient of friction:- Too smooth: May cause stick-slip behavior
- Too rough: Increases wear and friction
Aim for a moderately polished metal surface (Ra ~0.2–0.4 μm) for best sliding performance. -
Optimize Load and Speed Parameters
PTFE performs best under moderate loads and speeds. Keep the PV value (Pressure × Velocity) within manufacturer guidelines to avoid premature wear. -
Allow for Creep and Thermal Expansion
PTFE’s low stiffness and high thermal expansion can lead to creep under load. Use backing materials or encapsulation to manage deformation. -
Consider Lubrication (if Needed)
While PTFE is often self-lubricating, in demanding applications, a dry lubricant like graphite or MoS₂ can enhance longevity.
Real-World Applications of Low Friction PTFE
Thanks to its ultra-low friction and chemical inertness, PTFE is widely used across industries that demand smooth, efficient, and reliable motion. Here are some key applications:
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Bearings and Bushings
- Used in: Sleeve bearings, thrust washers, plain bushings.
- Benefits: Eliminates the need for external lubrication, reduces noise, and enables long service life.
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Seals and Gaskets
- Used in: Dynamic seals, valve stem packing, hydraulic piston rings.
- Benefits: Maintains tight tolerances and smooth movement between parts.
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Conveyor Systems and Wear Strips
- Used in: Conveyor belt guides, chutes, and hopper linings.
- Benefits: Lower drag, reduced wear, quieter operation.
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Aerospace and Defense
- Used in: Control surface bearings, sliding joints, fuel system liners.
- Benefits: Low outgassing and thermal resistance.
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Electronics and Semiconductor Manufacturing
- Used in: PTFE guide rails, low-friction slide pads, cable insulation.
- Benefits: Remains chemically stable under plasma exposure.
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Medical and Laboratory Equipment
- Used in: Syringe plungers, pump seals, sample transport mechanisms.
- Benefits: Hygienic and frictionless movement in delicate instruments.
Conclusion
PTFE stands out as a benchmark for low-friction materials due to its remarkable properties and versatility across various applications. Understanding its coefficient of friction, how it compares to alternatives, and the factors that influence its performance can help engineers and designers make informed decisions when specifying PTFE for their projects. Whether in bearings, seals, or medical equipment, PTFE continues to play a vital role in enhancing efficiency, reliability, and longevity in numerous industries.
