Both PA6 and PA66 are thermoplastics valued for being light, tough, and chemically resistant, finding extensive use in fibers (civil, industrial, fishing nets), injection molded parts (durable, wear-resistant components), and films. Despite their similarities, subtle differences in their properties dictate distinct application suitability.
Physical Properties & Production: Both are translucent, milky-white crystalline polymers. Their production differs fundamentally: PA6 is produced via the ring-opening polymerization of caprolactam (often derived from petroleum benzene), while PA66 is synthesized by the polycondensation of hexamethylene diamine and adipic acid.
Performance Comparison: PA6 has a lower melting point and wider processing range than PA66. It generally features better impact resistance and solubility but higher hygroscopicity. The molecular structure of PA66 is more symmetrical, allowing for stronger intermolecular hydrogen bonding. This results in a higher dynamic crystallization rate during spinning (about 20 times that of PA6), leading to higher tensile strength in industrial yarns (e.g., 9.7 g/d for PA66 vs. 9.0 g/d for PA6 under similar conditions). This structural difference underpins PA66’s superior mechanical strength and thermal resistance, whereas PA6’s advantages lie in better impact performance and processability.