What Are the Differences between PA6 and PA66?

PA is one of the common engineering plastics, while PA6 and PA66 are the most common nylon materials. The two have similar structures and have a lot in common. So what is the difference between the two? Come find out with us today.

1. Background of PA6 and PA66

PA66 is a PA66 polymer that Carothers successfully polycondensed with adipic acid and hexamethylene diamine in 1935. From 1936 to 1937, the process of making PA66 by melt spinning was discovered, and it was commercialized by the American DuPont Company at the end of 1939.

PA6 is a PA6 polymer synthesized by the German IG company Schlak using a single caprolactam as the raw material ε-aminocaproic acid as an initiator to heat and synthesize. In 1939, the experimental production of PA6 fiber was carried out, and the commercialization was completed by the German company Farben in 1943.

2. The structure of PA6 and PA66

To analyze the difference between them, we must start with their structures. As we all know, PA6 is formed by ring-opening polymerization of caprolactam, while nylon PA66 is obtained by the condensation polymer of hexamethylenediamine and adipic acid. PA6 and PA66 have the same molecular formula, but different structural formulas, and it is precisely because of this difference that their properties are different, such as different intermolecular hydrogen bonding forces.

The number of hydrogen bonds in PA66 is more than that in PA6, and the intermolecular force of PA66 is stronger than that of PA6, so PA66 is better than PA6 in thermal properties (so the processing temperature is higher), the rigidity of PA66 is better than that of PA6, and the toughness of PA6 is better than PA66, the water absorption speed of PA6 is faster than that of PA66, and the difference in properties between PA6 and PA66 is mainly caused by the above hydrogen bond factors.

3. Performance of PA6 and PA66

The melting point of PA66, such as PA 66 gf 15, is 260℃~265℃, and the glass transition temperature (dry state) is 50℃. The density is 1.13~1.16g/㎤.

PA6 is a translucent or opaque milky white crystalline polymer particle with a melting point of 220°C, a thermal decomposition temperature of more than 310°C, a relative density of 1.14, a water absorption rate of 1.8% (24h in water at 23°C), and excellent wear resistance and self-lubrication. high mechanical strength, good heat resistance, good electrical insulation performance, excellent low temperature performance, good self-extinguishing chemical resistance, especially excellent oil resistance.

Compared with PA66, PA6 is easy to process and form, the surface gloss of the product is good, and the operating temperature range is wider, but the water absorption rate is higher and the dimensional stability is poor. Like PA6 gf20, it has low rigidity, low melting point, can be used for a long time in harsh environments, can still maintain sufficient stress in a wide temperature range, and the continuous use temperature is 105 °C.

In general, the performance differences between PA66 and PA6 are as follows:

Mechanical properties: PA66 > PA6;

Heat medium performance: PA66 > PA6;

Price: PA66 > PA6;

Melting point: PA66 > PA6;

Water absorption: PA66 < PA6;

Weather resistance: PA66 < PA6;

Condensation time: PA66 < PA6;

Forming processability: PA66 < PA6.