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1. Chemical Structure and Basic Properties (PA6 vs PA66)
PA6 (Nylon 6)
- Monomer and Polymerization: Synthesized via ring-opening polymerization of ε-caprolactam, with amide groups separated by 5 carbon atoms in the molecular chain.
- Molecular Characteristics: Loosely packed molecular chains with higher polarity due to more amide bonds, leading to higher water absorption (saturation ~9-10%).
-
Crystallinity: ~30-40%, lower than PA66, resulting in better toughness but lower rigidity.
PA66 (Nylon 66)
- Monomer and Polymerization: Produced by polycondensation of adipic acid and hexamethylenediamine, with amide groups spaced by 6 carbon atoms and higher symmetry.
- Molecular Characteristics: Tighter molecular packing, higher hydrogen bond density, and crystallinity (40-50%), contributing to superior mechanical strength and heat resistance.
- Water Absorption: Saturation ~7-8%, slightly lower than PA6, but still sensitive to humidity.
2. Basic Performance Comparison of PA6 vs PA66
Property |
PA6 |
PA66 |
|
Mechanical Strength |
High, but slightly lower than PA66 |
Higher (better tensile/flexural strength) |
|
Heat Resistance |
Melting point ~220°C |
Melting point ~260°C (more heat-resistant) |
|
Toughness/Impact Resistance |
Better (especially at low temperatures) |
More brittle (requires modification) |
|
Water Absorption |
Higher (causes dimensional changes) |
Slightly lower (but still notable) |
|
Processability |
Easier (better flow) |
Requires higher temperatures (higher energy consumption) |
3. Mechanical Properties of PA6 vs PA66
| Performance Metric | PA6 (Unmodified) | PA66 (Unmodified) | Key Difference Reason |
| Tensile Strength | 70-80 MPa | 80-90 MPa | PA66’s higher crystallinity & hydrogen bonding |
| Flexural Modulus | 2.5-3.0 GPa | 3.0-3.5 GPa | PA66’s more rigid molecular chains |
| Notched Impact Strength | 5-8 kJ/m² | 4-6 kJ/m² | PA6’s greater molecular flexibility |
| Heat Deflection Temp (HDT) | 60-70°C (1.8 MPa) | 80-90°C (1.8 MPa) | PA66’s higher melting point (260°C vs. 220°C) |
4. Processing Parameters & Cost Factors
Processing Comparison of PA6 vs PA66
|
Parameter |
PA6 |
PA66 |
|
Injection Temperature |
230-280°C |
260-320°C |
|
Mold Temperature |
60-90°C |
70-120°C |
|
Drying Conditions |
80°C × 4h (moisture ≤0.1%) |
80°C × 4-6h (moisture ≤0.1%) |
|
Shrinkage Rate |
1.0-1.5% |
1.2-1.8% |
Cost Breakdown:
- Material Cost: PA66 is ~15-25% more expensive than PA6 (due to adiponitrile supply chain, e.g., 2021 shortage caused price surges).
- Processing Energy: PA66 requires 10-15% higher energy due to elevated temperatures.
- Rejection Rate: PA66 is more sensitive to process variations (e.g., bubbles from insufficient drying), increasing scrap costs.
5. Material Selection & Applications
Preferred PA6 (Cost-Performance Balance)
- Automotive: Door handles, interior parts (non-high-temperature zones).
- Electronics: Sockets, cable ties (good insulation).
- Consumer Goods: Gears, toys (high toughness required).
- Films/Fibers: Packaging, fishing nets (superior elongation).
Preferred PA66 (High-Performance Needs)
- High-Temp Parts: Engine components, cooling fans.
- Structural Parts: Gears, bearings (high-load scenarios).
- Industrial Parts: Wear-resistant guides, fasteners (long-term stability).
FAQ
Can annealing improve PA6 to match PA66’s performance?
Annealing (e.g., 120°C × 2h) increases crystallinity, improving rigidity and dimensional stability, but cannot reach PA66’s heat resistance.
How to quickly distinguish PA6 and PA66 products?
Burn Test:
- PA6: Blue flame, continuous drips, celery-like odor.
- PA66: Yellow flame, faster drips, burnt wool smell.
Phone
+86-0769-86066062
info@kehuimold.com
