How to correctly identify and choose between modified PA6 and PA66 (Part 1)?

How to correctly identify and choose between modified PA6 and PA66 (Part 1)?

With the increasing maturity of modified nylon R&D technology, the application scope of PA6 and PA66 has gradually expanded. Many plastic product manufacturers or users of nylon plastic products are unclear about the differences between PA6 and PA66. Additionally, since there are no obvious visual distinctions between PA6 and PA66, this has led to much confusion. How can PA6 and PA66 be distinguished, and how should they be selected?

First, Tips for Identifying PA6 and PA66:
When burned, both PA6 and PA66 emit a smell similar to burnt wool or nails. PA6 produces a yellowish flame, while PA66 burns with a blue flame. PA6 has better toughness, is cheaper than PA66, and has a lower melting point (225°C). PA66 offers higher strength, better wear resistance, and a higher melting point (255°C).

Second, Differences in Physical Properties:

• PA66: Melting point: 260–265°C; glass transition temperature (dry state): 50°C; density: 1.13–1.16 g/cm³.
• PA6: Semi-transparent or opaque milky-white crystalline polymer pellets; melting point: 220°C; decomposition temperature: above 310°C; relative density: 1.14; water absorption (24 hours in water at 23°C): 1.8%. It has excellent wear resistance and self-lubrication, high mechanical strength, good heat resistance and electrical insulation properties, good low-temperature performance, self-extinguishing properties, and chemical resistance—especially oil resistance.

Compared to PA66, PA6 is easier to process and mold, offers better surface gloss in finished products, and has a wider usable temperature range. However, it has higher water absorption and poorer dimensional stability. It is less rigid, has a lower melting point, and can be used for long periods in harsh environments. It maintains good stress resistance across a wide temperature range, with a continuous service temperature of 105°C.

Third, How to Decide Whether to Use PA66 or PA6?
Performance comparison between PA6 and PA66:

• Mechanical properties: PA66 > PA6
• Thermal performance: PA66 > PA6
• Price: PA66 > PA6
• Melting point: PA66 > PA6
• Water absorption: PA6 > PA66

Fourth, Differences in Application Scope:

• PA6 engineering plastics have high tensile strength, good impact resistance, excellent wear resistance, chemical resistance, and a relatively low friction coefficient. Through modifications such as glass fiber reinforcement, mineral filling, or flame retardant additives, their overall performance can be further enhanced. They are mainly used in the automotive industry and electronics/electrical fields.
• PA66 has superior overall performance, including high strength, rigidity, impact resistance, oil and chemical resistance, wear resistance, and self-lubrication. It particularly excels in hardness, rigidity, heat resistance, and creep resistance. Due to its higher strength compared to PA6, PA66 is more commonly used in industrial applications such as tire cord production.

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