Nylon 6 (PA6) and Nylon 66 (PA66) are the two most widely used engineering thermoplastics in injection molding — yet choosing between them requires balancing moldability, mechanical performance, and cost. This guide focuses specifically on their injection molding behavior, not just data sheet numbers.
Melt Temperature and Processing Window
PA6 melts at approximately 220°C with a processing range of 230-280°C. PA66 melts higher at 260°C with processing between 270-300°C. The wider processing window of PA6 makes it considerably more forgiving — mold temperature variation of 10-20°C won’t ruin a PA6 shot, but it can cause dramatic property variation in PA66.
| Processing Parameter | Nylon 6 (PA6) | Nylon 66 (PA66) |
|---|---|---|
| 熔點 | 220°C | 260°C |
| Processing Range | 230-280°C | 270-300°C |
| 模具溫度 | 80-90°C | 80-100°C |
| 模具收縮 | 0.8-1.5% | 1.0-2.0% |
| Drying Required | 80°C / 4h | 80°C / 4-8h |
Shrinkage and Warpage
PA66 exhibits higher and more anisotropic mold shrinkage (1.0-2.0%) compared to PA6 (0.8-1.5%). For parts with uneven wall thickness, PA66 warps significantly more. When we design molds for PA66 parts, we budget 20-30% more compensation in mold dimensions. Adding 30% glass fiber reinforcement reduces shrinkage for both grades to approximately 0.3-0.7%.
Drying Is Critical
Both PA6 and PA66 are hygroscopic — they absorb moisture from the atmosphere. Injection molding wet nylon results in splay marks, hydrolytic degradation, and catastrophic property loss. PA66 is more sensitive, requiring 4-8 hours at 80°C versus PA6’s typical 4 hours. Residual moisture above 0.2% will visibly degrade part quality.
Application Selection Guide
Choose PA6 when: easier processing matters, you need better surface finish, warpage control is critical for large parts, or cost sensitivity is high.
Choose PA66 when: elevated temperature strength is needed (up to 180°C vs 120°C), creep resistance under sustained load is critical, or stiffness retention at temperature matters.
常見問題
Why does PA66 cost more than PA6?
PA66 has more expensive monomers (adipic acid and hexamethylene diamine) compared to PA6’s caprolactam. The higher processing temperatures also increase energy cost. In our experience, PA66 parts typically cost 15-25% more than equivalent PA6 parts.
Can I switch from PA66 to PA6 in an existing mold?
Not without evaluating shrinkage differences. PA6’s lower shrinkage means parts come out slightly larger. Process adjustments alone may work for non-critical dimensions, but tight tolerances likely require mold rework.
Which grade has better chemical resistance?
Both grades have similar chemical resistance. PA66 has slightly better resistance to hydrocarbons and oils at elevated temperatures. Neither performs well with strong acids or oxidizing agents.
Do you injection mold both PA6 and PA66?
Yes. We injection mold both PA6 and PA66, including glass-fiber-reinforced variants, from prototype through low-volume production with 15-25 day tooling lead times.
Need injection molded PA6 or PA66 parts?
We provide prototype and production molding for both nylon grades with full mold design support.
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