PA6 VS PA66

2026-07-23

Introduction

Nylon 6 and Nylon 66 are two of the most widely used engineering plastics in automotive, electrical, industrial, and consumer applications. Both materials belong to the polyamide (PA) and offer excellent mechanical strength, wear resistance, and chemical resistance.

However, differences in their molecular structures result in significant variations in thermal performance, mechanical properties, moisture absorption, dimensional stability and processing characteristics.

Choosing the right nylon material is critical for applications requiring long-term durability, high strength, and reliable performance under demanding conditions.

1. Molecular Structure Difference Between Nylon 6 and Nylon 66

The main difference between Nylon 6 and Nylon 66 comes from their polymer structures.

PA 6, also known as Nylon 6, is polymerized from caprolactam. Its irregular molecular structure gives it the following properties:

Better impact toughness
Better melt flow
Easier processing

PA 66, also known as nylon 6 or PA 6,6, is an engineering plastic formed by the polymerization of hexamethylenediamine and adipic acid. Its more symmetrical and regular molecular structure gives it the following properties:

Higher crystallinity
Higher melting temperature
Better heat resistance
Improved dimensional stability

2. Thermal Performance Comparison of PA

Compared to other cost effective plastics, polyamide materials offer higher heat resistance; PA66 typically has better thermal properties than PA6.

The following comparison is between the standard unfilled UBE 1013B nylon 6 produced by Japan Ube Chemicals and the standard unfilled Zytel 101L PA66 produced by Celanese Nanjing plant.

2.1 Heat Deflection Temperature (HDT) of Nylon @ 0.45 MPa

PA6 - 155℃
PA66 - 200℃

2.2 Melting Point of Nylon

PA6 - 215℃-225℃
PA66 - 262℃

2.3 Coefficient of Linear Thermal Expansion (CLTE) of Nylon

PA6 - ~90–100 ×10⁻⁶/°C
PA66 - 83 ×10⁻⁶/°C

Advantage: Nylon 66

Because of its higher crystallinity and stronger intermolecular hydrogen bonding, Nylon 66 maintains mechanical strength better at elevated temperatures.

Typical applications requiring PA66 include:

Engine compartment components
Automotive connectors
Electrical housings
High-temperature brackets
Structural parts

3. Mechanical Properties Comparison of PA

PA resin is widely used due to its comprehensive mechanical properties, including high tensile strength, excellent impact resistance, and outstanding durability. In terms of mechanical properties, the disadvantage of nylon compared to other engineering plastics lies in its moisture absorption rate; unreinforced PA resin has a high moisture absorption rate and therefore must be thoroughly dried before processing.

Comparison of the Mechanical Properties of Nylon:

Property	UBE 1013B Nylon 6	Zytel 101L NC010 Nylon 66	Test Standard	Unit
Tensile Strength	80	82	ISO 527	MPa
Tensile strain at break	30	45	ISO 527	%
Tensile modulus	2.9	3.1	ISO 527	GPa
Flexural strength	110	90	ISO 178	MPa
Flexural modulus	2.7	2.8	ISO 178	GPa
Water absorption at equilibrium	3.0	2.6	-	%
Charpy notched impact strength	6.0	5.5	ISO 179	kJ/㎡

As can be seen from the table above, PA 66 resin significantly outperforms PA 6 in terms of strength and stiffness, while PA 6 outperforms PA 66 in terms of flexibility and impact resistance.

Nylon 66 Advantages

PA66 typically provides:

Higher tensile strength
Higher modulus
Better creep resistance
Better load-bearing capability

This makes it suitable for components exposed to continuous mechanical stress.

Nylon 6 Advantages

PA6 provides:

Higher toughness
Better impact absorption
Improved flexibility

It is often preferred when impact resistance is more important than maximum rigidity.

4. Moisture Absorption and Dimensional Stability

Like all polyamide materials, PA66 and PA6 exhibit poorer water absorption and dimensional stability compared to conventional plastics.

Property	UBE 1013B Nylon 6	Zytel 101L NC010 Nylon 66
Moisture Absorption	3%	2.6%
Molding shrinkage	1.45%	1.4%
Property Change After Water Absorption	3%	1.2%

Higher moisture absorption can affect:

Part dimensions
Mechanical strength
Electrical properties

Therefore, PA66 is often selected for precision components where dimensional control is critical.Typical examples:

Electrical connectors
Automotive clips
Sensor housings
Precision mechanical parts

5. Typical Applications

Nylon 66 Applications

Nylon 66 is commonly used for:

Automotive electrical connectors
Fuse boxes
Engine compartment components
Structural brackets
High-load mechanical parts

Main advantages:

✓ Higher heat resistance
✓ Higher strength
✓ Better creep resistance
✓ Superior dimensional stability

Nylon 6 Applications

Nylon 6 is commonly used for:

Automotive covers and housings
Fan blades
Cable ties
Mechanical components
Industrial gears
Consumer products

Main advantages:

✓ Excellent toughness
✓ Good processing performance
✓ Cost-effective solution

Conclusion

Nylon 6 and Nylon 66 are both high-performance engineering plastics, However, there are significant differences in performance. The following is a summary of their main performance and application differences.

Nylon 6 offers excellent toughness, easier processing, and cost advantages, making it suitable for general mechanical components and applications requiring impact resistance.

Nylon 66 provides higher strength, better heat resistance, and superior dimensional stability, making it the preferred choice for demanding automotive, electrical, and industrial applications.

Selecting the correct nylon grade ensures better product reliability, longer service life, and optimized manufacturing performance.

References and Notes

Mitsubishi ,"PA6和PA66材料特性",Mitsubishi Chemical advanced material AG, 23/06/2026
UBE,"UBE nylon 1013B polyamide 6 technical data sheet",UBE corporation, 23/06/2026
Celanese,"Zytel 101L NC010 nylon resin technical data sheet ",Celanese corporation, 23/06/2026

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