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21 clicksIts low-temperature toughness is strongly affected by moisture absorption.
PA612 belongs to long-carbon-chain polyamides with lower amide group density.
It features inherently superior low-temperature ductility, much lower water absorption, and milder performance fluctuation under alternating humidity & low temperature. Its ductile-brittle transition temperature is below -50°C.
| Test Item | PA66 | PA612 |
|---|---|---|
| Ductile-brittle transition temperature (neat resin, dry) | -20 ~ -25℃ | ＜ -50℃ |
| Saturated water absorption (23℃) | 7.5 ~ 8.5 % | 3.0 ~ 3.3 % |
| Low-temperature toughness (unmodified raw material) | Poor; brittle fracture easily occurs below -25℃ | Good; maintains ductility at -40℃ |
| Toughener dosage for stable -40℃ service | 15 ~ 22 wt% POE-g-MAH; obvious loss of modulus & hardness | 6 ~ 12 wt% POE-g-MAH; balanced rigidity & low-temperature toughness |
| Influence of moisture on low-temperature impact | Extremely significant: dry state low-temperature impact drops sharply | Weak influence; consistent toughness in dry & conditioned state |
| Low-temperature dimensional stability | Poor; prone to shrinkage/deformation under temperature & humidity cycling | Excellent; low shrinkage & low warpage |
| Modulus variation at low temperature | Modulus rises sharply; material becomes stiff | Moderate modulus increase; less tendency to harden |
| Heat resistance (HDT, unfilled) | Higher (~80–90℃ dry) | Moderate (~60–70℃ dry) |
| Melting point | 260~265℃ | 215~220℃ |
| Cost level | Medium | Medium-High |
2.Core Technical Analysis
Intrinsic Material Difference
The higher density of amide bonds in PA66 leads to stronger intermolecular hydrogen bonding. Molecular chains freeze easily under low temperature, resulting in low intrinsic cold resistance.
PA612 has longer aliphatic segments between amide groups. Molecular chain mobility remains maintained at sub-zero temperatures, delivering natural low-temperature toughness.
Modified Material Scheme for -40°C Environment
Toughened PA66
Can meet -40℃ anti-impact requirement, but needs high dosage of elastomer. Drawbacks: large gap between dry & wet impact performance, high water absorption limits precision parts. Advantage: higher heat deflection temperature.
Toughened PA612
Lower toughener loading is sufficient to pass -40℃ impact test. Small difference between dry/wet mechanical properties. Ideal for precision components with strict dimensional stability under wide temperature & humidity variation.
Glass-Filled System Key Reminder
For GF-reinforced grades (GF15/GF20/GF30):
Both materials face toughening difficulty after adding glass fiber.
Under identical toughener formulation, PA612-GF always shows better -40℃ notched impact than PA66-GF.
3.Application Selection Guidance
Choose toughened PA66:
Structural parts requiring high heat resistance, limited budget, non-precision components, no long-term high humidity exposure.
Choose PA612 (toughened grade):
Precision sensors, hydraulic fittings, valve components, outdoor equipment exposed to -40℃ & humidity alternation, parts requiring stable size and consistent low-temperature toughness.
4.Short Version (for customer email & quotation)
Unmodified PA66 embritles around -25°C.
High content of MAH-grafted elastomer is required to realize -40°C impact resistance, and its low-temperature performance varies greatly with moisture content.
As a long-chain nylon, PA612 owns inherent excellent low-temperature ductility with ductile-brittle transition temperature below -50°C.
It absorbs far less water, needs less toughener to satisfy -40°C working conditions, and delivers stable mechanical properties under dry and humid environments.
* The application cases shown may not fully match your target products. Please inform us of your specific requirements, and we will assist you in material selection.
