Differences between PA6(Nylon6), PA66(Nylon66), PA610(Nylon610) and PA612(Nylon612)?

PA6 vs PA66 vs PA610 vs PA612: Core Differences

The four are all aliphatic polyamides (nylons), differing in monomer structure, amide group density, and resulting properties—trading strength, heat resistance, moisture absorption, and cost.

1. Chemical Structure & Synthesis

1. PA6 (Nylon 6): Polymerized from caprolactam (single monomer); repeating unit: –[CO–(CH₂)₅–NH]–.

2. PA66 (Nylon 66): Polycondensed from hexamethylenediamine + adipic acid (two monomers); unit: –[CO–(CH₂)₄–CO–NH–(CH₂)₆–NH]–.

3. PA610 (Nylon 610): Hexamethylenediamine + sebacic acid (C10 diacid); longer hydrophobic chains than PA6/66.

4. PA612 (Nylon 612): Hexamethylenediamine + dodecanedioic acid (C12 diacid); longest chains, lowest amide density in this group.

2. Key Property Comparison

 

Property	PA6	PA66	PA610	PA612
Melting Point (°C)	220–225	260–265	220–225	215–218
Density (g/cm³)	1.13–1.15	1.14–1.15	1.08–1.10	1.04–1.06
Water Absorption (24h, %)	1.8–1.9	1.4–1.5	0.4–0.5	0.3–0.4
Tensile Strength (MPa)	74–78	80–83	55–60	50–55
Stiffness (Modulus)	Medium	Highest	Lower	Lowest
Toughness (Dry/Wet)	High (drops when wet)	Very High (stable)	Excellent (low moisture impact)	Best (retains flexibility at -40°C)
Dimensional Stability	Poor (high moisture)	Fair	Good	Excellent (precision parts)
Chemical Resistance	Good (bases, oils)	Good (bases, oils)	Better (weak acids, hydrolysis)	Best (fuels, solvents, outdoor)
Cost	Lowest	Low	Medium	Highest

 

3. Performance Tradeoffs

1. : Best flowability, lowest cost; high water absorption limits precision use.

2. : Highest strength, heat resistance, and abrasion resistance; stiff, moderate moisture absorption.

3. : Balances low moisture, flexibility, and cost; better outdoor stability than PA6/66.

4. : Lowest water absorption, best low-temperature toughness, and dimensional stability; premium price, lower heat resistance.

4. Typical Applications

1. : Textiles, fishing lines, gears, bearings, automotive interior parts (low-cost, high-toughness).

2. : Engine components, electrical connectors, power tools, industrial gears (high heat/strength).

3. : Toothbrush bristles, precision gears, electrical insulation, outdoor parts (low moisture, good weathering).

4. : High-end toothbrushes, medical devices, fuel system components, seals, cables (precision, low temp, chemical resistance).

5. How to Choose

1. High strength/heat: PA66

2. Low cost/easy processing: PA6

3. Outdoor/wet environment: PA610

4. : Precision/low-temperature: PA612