PA6 vs PA66 Nylon: Differences, Properties & Which to Choose
Both are nylon, both replace metal in demanding parts - but PA6 and PA66 diverge on melting point, moisture behaviour and cost in ways that matter for your design.
Two Nylons, Different Trade-Offs
PA6 (Nylon 6) and PA66 (Nylon 66) are both polyamides widely used to replace metal in automotive, electrical and industrial parts, but they are produced through different chemistries and behave differently under heat, moisture and load. Choosing between them affects processing window, dimensional stability and long-term cost.
Key Differences at a Glance
| Property | PA6 | PA66 |
|---|---|---|
| Melting point | ~220°C | ~260°C (higher) |
| Moisture absorption | Slightly higher | Slightly lower, more dimensionally stable |
| Impact strength (dry) | Generally higher | Slightly lower but improves with additives |
| Stiffness & heat resistance | Good | Higher |
| Processing window | Slightly wider, easier to process | Narrower, needs tighter process control |
| Typical cost | Generally lower | Generally higher |
Where PA6 Is the Better Fit
PA6 is often preferred where good impact strength, easier processing and lower cost matter most - common in general industrial components, cable ties, and parts that don't see continuous high-temperature exposure.
Where PA66 Is the Better Fit
PA66's higher melting point and better dimensional stability under heat make it the preferred choice for under-the-hood automotive components, electrical connectors near heat sources, and parts that must hold tight tolerances across a range of operating temperatures.
Moisture Absorption Matters More Than People Expect
Both PA6 and PA66 absorb ambient moisture, which affects mechanical properties and dimensions over time - PA66 absorbs somewhat less, giving it an edge in dimensionally critical applications, but both should be conditioned or dried appropriately before precision moulding.
Improving Either Grade With Compounds
Both PA6 and PA66 are commonly reinforced with glass fibre for added stiffness, or toughened with impact modifiers such as EPDM-g-MA and POE-g-MA for cold-impact performance - the right compound formulation often matters more to final part performance than the base PA6-vs-PA66 choice alone.
Get grade recommendations and technical datasheets from Siya Polymer & Speciality Chemicals's engineering plastics range.
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