Nylon (PA6) vs Nylon 66 (PA66)
Nylon 6 (PA6) and Nylon 66 (PA66) are the two workhorse polyamides for gears, bushings and wear parts. They're close in properties but differ in crystallinity: PA66 has a higher melting point and tends to run a bit stiffer and more heat- and wear-resistant, while PA6 is slightly tougher and easier to process. Both absorb moisture, which shifts their properties in service.
The verdict
Choose Nylon 66 (PA66) for hotter, higher-wear duty — gears and bushings where its higher melting point and stiffness pay off (rated ~100°C with higher melt point). Choose Nylon 6 (PA6) when toughness, impact resistance and easier processing matter, and the slightly higher heat-deflection rating here (110°C nominal) suits the part.
Side-by-side data
| Property | Nylon (PA6) | Nylon 66 (PA66) |
|---|---|---|
| Category | Engineering Plastic | Engineering Plastic |
| Density (g/cm³) | 1.14 | 1.14 |
| Tensile strength (MPa) | 80 | 83 |
| Yield strength (MPa) | 80 | 80 |
| Elongation (%) | 50 | 60 |
| Hardness | R120 | R120 |
| Max service temp (°C) | 110 | 100 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 0.25 | 0.25 |
| Typically used for | Gears, bushings & wear parts | Gears, bushings & wear parts |
Which should you choose?
Choose Nylon 6 (PA6) when…
- Impact toughness and fatigue resistance are priorities for the wear part
- Easier processing and good surface finish help molding or machining
- The part is a gear, bushing or bearing under moderate, cyclic load
- Higher elongation isn't required but toughness margin is welcome
- You want a slightly lower-cost, widely available polyamide grade
- The application can tolerate moisture uptake with proper design
Choose Nylon 66 (PA66) when…
- Service runs hot — PA66's higher melting point gives a better margin in heat
- You need slightly higher stiffness and tensile (~83 vs 80 MPa nominal)
- Wear resistance and surface hardness for gears and bushings are critical
- Better creep resistance under sustained load is wanted
- Higher elongation (~60% vs 50%) helps with toughness at the molded grade
- Lower cost here (1.5 vs 2.0) helps high-volume mechanical parts
Key differences that matter
- PA66 has a higher melting point than PA6 — the key practical difference, giving better short-term heat and wear performance.
- Mechanical values are close: PA66 ~83 MPa tensile / 60% elongation versus PA6 ~80 MPa / 50% nominal.
- PA6 is generally tougher and easier to process; PA66 is stiffer and more wear-resistant.
- Both are hygroscopic — they absorb moisture, which lowers stiffness/strength and changes dimensions; design and dry accordingly.
- Both share thermal conductivity ~0.25 W/m·K and are used for gears, bushings and wear parts.
- Glass-filled grades of either (e.g., PA66-GF30 elsewhere in the dataset) sharply raise stiffness and temperature capability when needed.
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Open the Material SelectorGet a Quote →Frequently asked questions
What's the real difference between Nylon 6 and Nylon 66?
Chemistry and crystallinity. PA66 has a higher, sharper melting point and tends to be stiffer, harder and more wear- and heat-resistant. PA6 is slightly tougher, absorbs moisture a bit faster, and processes more easily with a broader window. In many gear and bushing jobs they're interchangeable; the choice tightens when heat or toughness is critical.
Do both nylons absorb water, and does it matter?
Yes — both are hygroscopic and pick up moisture from air and service. Absorbed water acts as a plasticizer: it raises toughness but lowers stiffness and strength and swells the part dimensionally. For tight-tolerance gears or bushings you must account for moisture conditioning, and parts should be dried before molding.
Which is better for a gear that runs warm?
Nylon 66, because its higher melting point gives more thermal margin and better wear resistance at elevated temperature. PA6 is fine for cooler or impact-loaded gears. If the gear runs hot and loaded, a glass-filled PA66 grade raises stiffness and heat capability further than either unfilled grade.
Is one easier to machine or print?
PA6 is generally a bit easier to process and is common as a 3D-printing and cast nylon stock. Both list CNC machining; nylons machine reasonably but can absorb cutting heat and moisture, so parts may move after machining. Stress-relieve and condition tight-tolerance parts regardless of which grade you pick.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.