Long-chain polyamides (PA610, PA612, PA12, PA11)

Long-chain polyamides are PA610, PA612, PA12 and PA11, aliphatic polymers with low water absorption of 0,3–0,5 % (ISO 62, 24 h, 23 °C) versus 2,5 % in PA66 and 8–10 % in PA6. As a result, parts retain dimensional stability in humid environments, exhibit 2–3 times lower creep after conditioning, and withstand contact with fuel, hydraulic fluid and antifreeze at operating temperatures of 90–130 °C over the long term.

How long-chain PA differ from PA6 and PA66

The methylene group (–CH₂–) between the amide bonds is longer: in PA12 there are 11 atoms, in PA11 there are 10, in PA610 there are 9 (from ω-aminohexanoate). In PA6 there are 5, in PA66 there are 6. The longer the aliphatic chain, the lower the concentration of polar amide groups and the lower the water absorption. Dimensional change in a humid environment is 5–10 times smaller, while fatigue resistance under cyclic bending is higher. The trade-off is a lower melting temperature (178–222 °C versus 260 °C in PA66) and a lower modulus of elasticity in the dry state.

When to choose which grade

Parts in contact with water, antifreeze, fuel → PA612, PA12, PA11

Water absorption of 0,3–0,5 % ensures stability of clearances in valves, fittings and fuel lines. PA12 is the standard for automotive fuel lines (SAE J2260, ISO 4080).

Metal replacement for brackets and housings → PA610 GF50

A flexural modulus of 14–15 GPa (ISO 178) and a density of 1,42 g/cm³ deliver specific strength higher than aluminium casting, without the moisture-related drop seen in PA66 GF.

Precision gears and bushings operating without lubrication → PA66 GF30-15PTFE

Coefficient of friction against steel of 0,12–0,18 versus 0,30–0,40 in unfilled PA66. PV parameter up to 1,5 MPa·m/s. Bushings for conveyor rollers, mechatronics guides.

Flexible pipes, tubing, cable jacketing → unfilled PA12, Rilsan® PA11

Elongation at break of 200–300 %, fatigue resistance under cyclic bending. PA11 — aerospace hydraulic lines, medical catheters.

Contact with drinking water (FWA, WRAS, NSF) → PA12 GF50-FWA

Certified food/water approval grade for water supply fittings.

Series from Material Wizard

Examid® PA610 series — injection-moulding (PA610-L), extrusion (PA610E) and glass-filled (GF50) grades. The base is partially bio-based (sebacic acid from castor oil).

Examid® PA612-L1100 — the lowest water absorption in its class (0,3 % over 24 h), for precision parts in humid environments.

Examid® PA12, PA12 GF50-FWA — the standard for fuel lines, flexible pipes, contact with drinking water.

Rilsan® PA11 (Arkema) — high-end bio-PA. Aerospace and oil & gas flexible pipes, medical catheters. Fatigue endurance +30–50 % versus PA12 at RT.

Examid® PA66 GF30-15PTFE — self-lubricating compound. Assigned to the long-chain class by function (low friction, clearance stability without lubrication).

Limitations

The operating temperature is lower than for PA66 and PPA: PA12 — up to 90 °C over the long term, PA11 and PA610 — up to 110–130 °C, PA612 — up to 120 °C. For zones of 150 °C+ choose PPA or PA46. The price of long-chain PA is 1,5–3 times higher than PA66 due to the more expensive monomer. Drying before moulding is mandatory: 4 h at 80 °C, final moisture content < 0,1 %.