PA6 resins vs PA66 resins : Key Differences & Selection Guide (With Applications)

Property	PA6 (Nylon 6)	PA66 (Nylon 66)
Monomer	Caprolactam	Hexamethylenediamine + Adipic acid
Melting Point	220°C	260°C (Higher)
Water Absorption	High (≈10% saturation)	Moderate (≈8% saturation)
Rigidity/Strength	Good	Superior (High crystallinity)
Impact Resistance	Better (Low-temp toughness)	Good
Processing	Easier (Good flow)	Higher mold temp needed
Cost	Lower	Higher

✅ Key Takeaway: PA66 wins in strength/heat resistance, PA6 leads in toughness/cost.

High-Temperature Applications
- Choose PA66: Higher melting point (260°C vs 220°C), HDT 15-30°C higher. Ideal for engine components, high-temp connectors.
- Modification Tip: Glass-filled PA66 HDT >240°C vs PA6 ~200°C.
Mechanical Load Requirements
- Choose PA66: 10-20% higher tensile/flexural strength. Perfect for gears, bearings, structural brackets.
- Exception: For impact-critical parts (e.g., sports gear), use toughened PA6.
Humid/Wet Environments
- Avoid pure PA6: High water absorption causes dimensional instability (strength drops 50% when wet!).
- Solutions:
  - Need stability → PA66 (better property retention)
  - Must use PA6 → Moisture-resistant modification (e.g., nano-clay additives)
Cost-Driven Projects
- Choose PA6: 15-30% lower material cost + easier processing. Best for appliance housings, non-critical tools.
- 4. How Modification Solves Weaknesses?
  - PA6 Fixes:
    - Water absorption → Add desiccants (e.g., silane coupling agents)
    - Low HDT → Glass fiber/mineral reinforcement
  - PA66 Fixes:
    - Processing difficulty → Flow enhancers
    - Low-temp brittleness → Elastomer toughening