Why Lubricate Nylon?
Nylon’s natural surface properties include a relatively low coefficient of friction compared to many engineering plastics—but it’s not inherently self-lubricating. In moving-part applications like gears, bearings, slides, and cams, unlubricated nylon can experience accelerated wear, frictional heating, and stick-slip behavior. Lubricated nylon grades solve this by incorporating solid or liquid lubricants directly into the polymer matrix, creating parts that run smoothly for millions of cycles without external lubrication.
The lubricant additives work by forming a transfer film on the mating surface. As the nylon part moves, microscopic lubricant particles are released, coating both the nylon surface and the opposing metal or plastic surface. This film reduces the coefficient of friction from 0.35–0.40 (unmodified nylon on steel) down to 0.10–0.20, depending on the lubricant type and loading.
The Three Main Lubricant Types
| Lubricant | Typical Loading | COF (vs Steel) | Best Application |
|---|---|---|---|
| PTFE (Teflon) | 10–20% | 0.10–0.18 | High-speed bearings, low-load slides |
| MoS₂ (Molybdenum Disulfide) | 1–5% | 0.12–0.20 | High-load gears, thrust washers |
| Oil-filled | 2–8% | 0.08–0.15 | Precision bearings, low-noise applications |
PTFE-Filled Nylon
PTFE (polytetrafluoroethylene) is the most common solid lubricant for nylon. With a coefficient of friction as low as 0.04 in its pure form, PTFE particles dispersed throughout nylon create an extremely low-friction surface. PTFE-filled nylons are ideal for high-speed, low-to-moderate load applications where continuous sliding motion is required.
The limitation: PTFE reduces mechanical strength by 10–20% and increases cost. It also doesn’t perform as well as MoS₂ under very high contact pressures.
MoS₂-Filled Nylon
Molybdenum disulfide has a layered crystal structure similar to graphite—sheets that easily slide past each other. This makes it exceptional under high contact pressures where PTFE would be squeezed out. MoS₂-filled nylon is the go-to choice for gears, cams, and thrust washers operating under significant load.
MoS₂ also increases nylon’s crystallinity slightly, which can improve strength and stiffness—unlike PTFE which weakens the matrix. The dark gray/black color can be a consideration for visible parts.
Oil-Filled Nylon
Oil-filled nylons incorporate lubricating oil directly into the polymer during compounding. During operation, the oil slowly migrates to the surface, providing continuous lubrication throughout the part’s life. This “self-replenishing” characteristic makes oil-filled nylon excellent for sealed applications where relubrication is impossible.
Common oils include silicone, mineral oil, and synthetic hydrocarbon oils. The oil content is precisely controlled to avoid excessive migration that could contaminate surrounding components.
Wear Rate Comparison
| Nylon Grade | K-Factor (×10⁻⁸ mm³/N·m) | PV Limit (MPa·m/s) | Service Temp Range |
|---|---|---|---|
| PA6 Unfilled | 40–80 | 0.09–0.12 | -30°C to 85°C |
| PA6 + 15% PTFE | 5–12 | 0.15–0.25 | -40°C to 100°C |
| PA6 + MoS₂ | 8–15 | 0.20–0.35 | -30°C to 95°C |
| PA66 + Aramid + PTFE | 2–5 | 0.35–0.50 | -40°C to 120°C |
Design Guidelines for Lubricated Nylon Parts
- Surface finish of the mating part: Aim for 0.2–0.4 μm Ra on the steel/opposing surface. Rougher surfaces accelerate wear.
- Clearance: Allow 0.3–0.5% of the bearing diameter for thermal expansion and water absorption swell.
- Wall thickness: Maintain uniform wall thickness to avoid warpage that creates uneven wear patterns.
- Running-in period: Expect higher friction during the first 500–1000 cycles as the transfer film establishes.
- Combination with glass fiber: Adding glass fiber to lubricated nylon improves load capacity but increases wear on the mating surface. Use hardened steel (58+ HRC) for mating parts.
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Verwandte Artikel
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- Materialeigenschaften von Nylon: Eine vollständige technische Referenz
- Long Glass Fiber vs Short Glass Fiber Reinforced Nylon
Häufig gestellte Fragen
Can lubricated nylon eliminate the need for grease?
In many applications, yes. Properly selected lubricated nylon can run dry for the entire service life. However, for very high PV (pressure×velocity) applications exceeding the material’s PV limit, supplementary lubrication is still recommended.
Does oil-filled nylon contaminate surrounding parts?
High-quality oil-filled compounds use controlled-release formulations that minimize migration. For cleanroom or food-contact applications, solid lubricants like PTFE are generally preferred over oil-filled grades.
How do I choose between PTFE and MoS₂?
Use PTFE for high-speed, low-to-moderate load applications (conveyor bearings, slides). Use MoS₂ for high-load applications (gears, cams, thrust washers). For the most demanding applications, combination grades containing both are available.
Can I machine lubricated nylon stock shapes?
Yes. Lubricated nylon is available in rod, plate, and tube forms for CNC machining. The lubricant is distributed throughout the material, so machined surfaces retain the same performance as molded surfaces.
