Full definition
A family of semi-crystalline engineering thermoplastics known for excellent mechanical strength, wear resistance, toughness, and moderate heat resistance. Major grades: PA6 (cast or extruded, good all-round properties, tensile 70-85 MPa, economical), PA66 (higher melting point 260°C vs 220°C, better heat resistance, slightly stronger), PA12 (lowest moisture absorption, best chemical resistance, most flexible, for fuel lines), PA46 (highest heat resistance, for under-hood automotive). Key properties: self-lubricating (low COF 0.2-0.4 against steel), high fatigue endurance, good chemical resistance to hydrocarbons and weak alkalis. Limitation: hygroscopic — absorbs 2-8% moisture depending on grade, causing dimensional change and property reduction (PA12 least affected at 1.4%). Per ASTM D4066. Applications: gears, bearings, bushings, bearing cages, cable ties, chain guides, conveyor belt weft yarns, rollers, and structural components. Glass-fiber reinforced grades (GF30, GF50) significantly increase stiffness and strength. Brands: DuPont Zytel, BASF Ultramid, DSM Akulon.