PA - Polyamide (Nylon)

Polyamide (PA), commonly known as nylon, is a family of semi-crystalline engineering thermoplastics renowned for their exceptional mechanical strength, outstanding wear and abrasion resistance, and broad chemical compatibility. First commercialized by DuPont in 1938, polyamides have become one of the most widely used engineering plastics across automotive, electrical, industrial, and consumer applications.

The global polyamide market was valued at approximately $33 billion in 2024 and is projected to grow at a compound annual growth rate (CAGR) of 5.8% through 2030, driven by lightweighting initiatives in automotive manufacturing, expanding electrical and electronics production, and increasing demand for high-performance industrial components. Global PA production exceeds 8 million tonnes annually, with PA6 and PA66 accounting for over 90% of total consumption according to industry data from ICIS.

Polyamide resins comply with ASTM D4066 specifications for nylon injection and extrusion materials. Select grades are approved for food contact under FDA 21 CFR 177.1500 regulations, and UL-recognized grades meet UL 94 V-0 and V-2 classifications for electrical and electronic applications. Glass-filled grades are tested per ASTM D638 and ISO 527 for tensile properties.

Key properties of polyamide include:

• High mechanical strength and rigidity, with tensile strengths ranging from 70 to 85 MPa for unfilled grades and exceeding 190 MPa for glass-fiber-reinforced compounds.
• Excellent wear and abrasion resistance combined with a naturally low coefficient of friction, making PA ideal for gears, bearings, and sliding contact surfaces without external lubrication.
• Good chemical resistance to oils, greases, fuels, hydraulic fluids, and most organic solvents, enabling use in demanding automotive and industrial environments.
• High heat deflection temperatures — PA66 withstands continuous service up to 120°C unfilled and up to 260°C in glass-reinforced formulations.
• Excellent fatigue endurance and vibration damping, critical for dynamic load-bearing components such as gears, snap-fit assemblies, and spring elements.
• Good electrical insulating properties with high dielectric strength, making PA the material of choice for electrical connectors, terminal blocks, and circuit breaker housings.
• Self-extinguishing behavior in many grades without added flame retardants, meeting UL 94 V-2 requirements.

PA Types and Chemistry

Polyamides are characterized by the amide linkage (–CO–NH–) in their polymer backbone. The two most commercially significant types differ in their monomer chemistry and resulting performance profiles:

• PA6 (Polycaprolactam): Produced by ring-opening polymerization of caprolactam. PA6 offers excellent surface finish, good impact strength, and easier processing compared to PA66. It is the preferred grade for extrusion applications and parts requiring superior aesthetics.
• PA66 (Polyhexamethylene Adipamide): Produced by condensation polymerization of hexamethylenediamine and adipic acid. PA66 provides higher melting point (260°C vs. 220°C), better rigidity, and superior heat resistance compared to PA6, making it the standard choice for under-hood automotive components.
• PA12 (Polylaurolactam): A specialty polyamide with lower moisture absorption (0.25% vs. 2.5% for PA6), greater flexibility, and excellent chemical resistance. PA12 is used in fuel lines, brake tubing, and cable sheathing where dimensional stability in humid environments is critical.

Available Grades

Unfilled PA6 and PA66 provide the baseline balance of mechanical strength, toughness, and processability for general-purpose injection molding and extrusion. These grades are used in cable ties, fasteners, housewares, and industrial components where reinforcement is not required.

Glass-Fiber-Reinforced PA grades containing 15% to 50% glass fiber deliver dramatically increased tensile strength (up to 200 MPa), stiffness, and heat deflection temperature while reducing moisture-related dimensional change. These grades are essential for structural automotive components, electrical connectors, and industrial housings.

Mineral-Filled PA grades incorporate mineral fillers (talc, wollastonite, or glass beads) to improve dimensional stability, reduce warpage, and provide isotropic shrinkage behavior. These grades are preferred for precision parts, flat panels, and components requiring tight tolerances.

Impact-Modified PA grades contain elastomeric modifiers (typically EPDM or maleated polyolefins) that significantly increase notched impact strength, particularly at sub-zero temperatures. These grades are used in automotive bumper components, sports equipment, and power tool housings.

PA12 and Long-Chain Polyamides offer reduced moisture absorption, greater flexibility, and enhanced chemical resistance compared to PA6 and PA66. PA12 is the material of choice for fuel lines, pneumatic tubing, and wire and cable jacketing in automotive and industrial applications.

Heat-Stabilized and UV-Stabilized PA grades incorporate thermal and UV stabilizer packages for extended service life in demanding environments, including under-hood automotive applications and outdoor electrical housings.

Processing

Polyamides are processed primarily by injection molding and extrusion. PA6 is molded at melt temperatures of 230–280°C with mold temperatures of 40–90°C, while PA66 requires melt temperatures of 270–300°C with mold temperatures of 60–100°C. Thorough drying is critical before processing — PA resins must be dried to moisture content below 0.2% to prevent hydrolytic degradation and surface defects. Desiccant dryers at 80–90°C for 4–6 hours are standard practice.

Polyamides are also processed by extrusion (profiles, tubing, film), blow molding, rotational molding, and powder-bed fusion (SLS) 3D printing. Post-processing options include machining, ultrasonic welding, hot-plate welding, adhesive bonding, and painting.