This nylon 6 nylon guide explains practical considerations for material selection, design review, manufacturing, and sourcing decisions.
Nylon 6 vs Nylon 66 is one of the most common engineering plastic comparisons because the best choice depends on moisture exposure, strength targets, heat load, and processing needs.
In short, Nylon 6 is often preferred for toughness, easier processing, and lower cost, while Nylon 66 is usually chosen when higher heat resistance, stiffness, and creep performance matter more. For reinforced grades, see our PA66 GF30 guide and for fluid exposure, compare nylon chemical resistance.
Chemical Structure Differences
The fundamental difference between PA6 (Nylon 6) and PA66 (Nylon 66) lies in their molecular structure:
- Nylon 6: Made from caprolactam, has 6 carbon atoms in each repeating unit. Less crystalline structure.
- Nylon 66: Made from hexamethylenediamine and adipic acid, has two 6-carbon chains. More crystalline structure.
Mechanical Properties Comparison
| Property | PA6 | PA66 |
|---|---|---|
| Tensile Strength | 70-85 MPa | 80-100 MPa |
| Flexural Modulus | 2.5-3.0 GPa | 2.8-3.5 GPa |
| Elongation at Break | 30-100% | 15-60% |
| Notched Izod Impact | 50-100 J/m | 40-80 J/m |
| Melting Point | 220°C | 260°C |
| HDT at 1.8 MPa | 70°C | 90°C |
Moisture Absorption
Moisture absorption is critical for nylon applications:
| Condition | PA6 | PA66 |
|---|---|---|
| At 50% RH | 2.5-3.0% | 2.0-2.5% |
| Saturation | 8-10% | 6-8% |
Processing Characteristics
Nylon 6 Processing
- Melting Point: 220°C
- Processing Range: 240-280°C
- Mold Temperature: 40-80°C
Nylon 66 Processing
- Melting Point: 260°C
- Processing Range: 280-320°C
- Mold Temperature: 60-90°C
Applications by Material
Nylon 6 Applications
- Gears and sprockets
- Industrial monofilament
- Film and packaging
- Consumer products
Nylon 66 Applications
- Automotive under-hood components
- Electrical connectors
- High-temperature bearings
- Precision mechanical components
Reinforced Grades
Both materials are commonly reinforced with glass fiber:
| Grade | PA6 + GF30 | PA66 + GF30 |
|---|---|---|
| Tensile Strength | 140-160 MPa | 170-200 MPa |
| HDT (1.8 MPa) | 205°C+ | 250°C+ |
| Moisture Absorption | 1.0-1.5% | 0.8-1.2% |
Selection Summary
Choose Nylon 6 when:
- Impact resistance is critical
- Cost sensitivity is high
- Operating temperatures are moderate
Choose Nylon 66 when:
- Higher mechanical strength is required
- Elevated temperatures are expected
- Dimensional stability is critical
FAQ
When is Nylon 6 vs Nylon 66 — Engineering Plastic Selection Guide a good option?
Nylon 6 vs Nylon 66 — Engineering Plastic Selection Guide is a good option when fast iteration, complex geometry, low tooling cost, or low-volume production is more important than molded-part unit cost.
What should be checked before choosing Nylon 6 vs Nylon 66 — Engineering Plastic Selection Guide?
Check part size, material properties, surface finish, dimensional tolerance, heat exposure, load direction, and whether post-processing is required.
How does Nylon 6 vs Nylon 66 — Engineering Plastic Selection Guide compare with CNC machining?
3D printing can create complex shapes quickly, while CNC machining is often stronger for precise surfaces, tighter tolerances, and production-grade materials.
What affects the cost of Nylon 6 vs Nylon 66 — Engineering Plastic Selection Guide?
Cost depends on material, build volume, print time, layer height, support removal, finishing, inspection, and the number of parts in the build.
Related Reading
- Nylon vs Polypropylene: Material Selection Guide for Engineering Applications
- Acetal POM vs Nylon — Which Engineering Plastic Is Right for Your Application?
- Nylon vs PBT: Complete Engineering Thermoplastic Comparison
At a Glance
| Decision Point | PA6 | PA66 | Buyer Note |
|---|---|---|---|
| Impact / toughness | Strong | Strong | Compare actual part loading, not just resin family |
| Heat resistance | Good | Usually better | PA66 often wins when temperature margin matters |
| Moisture response | Higher | Also high | Conditioning will affect both grades |
| Best use | General engineering parts | Hotter or more demanding parts | Use the part environment to decide the grade |
Why Choose Nylon Plastic
Nylon Plastic can help buyers separate PA6 and PA66 decisions when the part needs a practical balance of heat, toughness and molding cost.
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