Quick Answer
Nylon is stronger, harder-wearing and cheaper than PTFE — but it absorbs moisture and swells, which changes its diameter in service. Use nylon for dry or oil-wetted mechanical duty at moderate temperature. Use PTFE wherever chemistry, temperature or dimensional stability in wet service matters.
Head-to-Head
| Property | PTFE | Nylon (Polyamide) |
|---|---|---|
| Continuous service temperature | -200°C to +260°C | -40°C to ~+100°C |
| Water absorption | < 0.01% | 1.5–3% (swells measurably) |
| Dimensional stability in wet service | Excellent | Poor — diameter grows with moisture uptake |
| Tensile strength | ~20–35 MPa | ~70–85 MPa |
| Abrasion resistance | Poor | Good |
| Coefficient of friction | 0.04–0.10 | 0.20–0.35 |
| Acid resistance | Excellent | Poor — attacked even by dilute acids over time |
| Density | 2.14–2.20 g/cm³ | ~1.14 g/cm³ |
| Relative cost | Higher | Lower |
The Moisture Problem
This is the point most often missed when nylon is substituted for PTFE to save cost. Nylon is hygroscopic — it absorbs water from both the atmosphere and the process fluid, and it swells as it does so. A nylon ball measured to specification when dry will be measurably larger after weeks in a wet line, and it also becomes softer and less stiff as it takes up moisture.
In a precision fit this is disqualifying. A check ball that grows can bind in its cage or stop seating correctly, and the failure appears gradually over weeks — which makes it hard to attribute to the material. PTFE absorbs under 0.01% water and simply does not do this.
Where Nylon Is the Right Choice
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Dry mechanical duty. Pneumatic circuits, mechanical linkages, dry check valves.
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Oil-wetted assemblies. Nylon handles oils and greases well and does not absorb them.
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Load-bearing applications. Roughly three times PTFE’s tensile strength and far better creep resistance.
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Cost-sensitive high-volume builds. Where media and temperature are benign, nylon does the job for less.
Where PTFE Is the Right Choice
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Any acid service. Nylon is attacked by acids including dilute ones over time.
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Wet or aqueous duty where dimensions matter. The swelling problem above.
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Above about 100°C. Nylon loses stiffness well before its stated limit.
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Solvent exposure. Nylon is attacked by phenols, some alcohols and strong oxidisers.
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Food and pharmaceutical contact. Virgin PTFE is the established specification.
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Very low friction. PTFE’s coefficient is a fraction of nylon’s, with no stick-slip.
A Practical Middle Ground
If nylon’s mechanical properties appeal but its chemistry does not, Delrin (POM/acetal) is usually the better comparison to make. Acetal has similar strength to nylon, far lower moisture absorption, and better dimensional stability — while still costing well below PTFE. It is a common and sensible substitution for mechanical check valve duty in non-aggressive media.
We manufacture nylon, Delrin and PTFE balls, so tell us the media, temperature and whether the line is wet, and we will point you at the one that actually fits.
Related Reading
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Nylon Balls (/nylon-ball) — product specifications
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Delrin (POM) Balls (/pom-delrin-ball) — the usual better alternative
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Delrin vs PTFE (/delrin-vs-ptfe)
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Engineering Plastic Balls (/engineering-plastic-balls)
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PTFE Ball Selection Guide (/ptfe-ball-selection-guide)