PA6 and PA66 are two common types of polyamide (nylon) resins. The main differences between them can be boiled down to the following:

Source of raw materials: PA6 is made from caprolactam (6-nylon) monomer, while PA66 is made from adipamide (6, 6-nylon) monomer. The two monomers differ slightly in their chemical structure, resulting in some of the performance differences between PA6 and PA66.

Melting temperature: PA66 has a higher melting point, usually between 250-260 degrees Celsius, while PA6 has a lower melting point, usually between 210-220 degrees Celsius. Therefore, PA66 has a high heat resistance.

Crystallization capacity: The crystallization capacity of PA66 is good, so it has high strength and rigidity. In contrast, PA6 has a weaker crystallization capacity, but has better toughness and impact resistance.

Hygroscopicity: Both PA6 and PA66 have certain hygroscopicity, but the hygroscopicity of PA6 is higher. Because the amide groups present in PA6 have better hygroscopicity, this also affects their physical and mechanical properties.

Toughness: In general, PA6 (nylon 6) shows better toughness than PA66 (nylon 66). In specific application scenarios, the toughness of PA66 can be improved by adding modifiers or adjusting processing conditions

In summary, although PA6 and PA66 are nylon materials, they have slight differences in melting temperature, crystallization capacity and hygroscopic properties, which also lead to their different characteristics and uses in practical applications. The choice of material should be determined according to the specific application requirements and performance requirements.