Desktop
Resin Data
PA66

Poliamida 66 (Nylon)

PA66·Polyamides·Semi-crystalline

PA66 (Nylon 66) is the "premium cousin" of PA6: same polyamide family but with HDT 255°C vs 220°C, more rigidity, better creep resistance under sustained load, and the #1 position in automotive under-hood applications — intake manifolds, engine covers, structural engine brackets, cable ties, premium electrical connectors. You also know it by its brand names: Zytel (DuPont, today Envalior), Vydyne (Ascend Performance Materials), Ultramid A (BASF), Durethan (Lanxess), Technyl (Solvay/DOMO).

Chemistry distinguishes it from PA6: instead of caprolactam (a single cyclic monomer), PA66 is made by condensing hexamethylenediamine (HMDA) + adipic acid — both with 6 carbons each (hence "66"). That more symmetric structure gives it higher crystallinity and better thermal/mechanical properties, but also makes it more expensive (~15–25%) and harder to process. Here we have compiled the reference ranges from the PDS, plus the questions that come up over and over on the shop floor: mandatory drying, PA66 vs PA6, GF35 for under-hood, hydrolysis and fatigue, and the dramatic history of the adiponitrile shortage (2018–2022).

Share your experience in the comments — ranges vary by manufacturer, grade (neat, GF, FR, HSHT) and ambient humidity, and collective discussion is what gets us out of trouble on the floor.

The ranges shown in these data tables were compiled by the MVPS team from various parameter sheets and literature, integrating the lower and upper limits for each material type.

This information must be carefully reviewed when developing injection molding processes. Final ranges and processing tolerances are the responsibility of the engineer in charge.

These ranges are not recommended for developing specific process tolerances. MVPS always recommends requesting and consulting the supplier's data sheet.

General Properties

Chemical StructureSemi-crystalline
Specific Gravity (Density)1.57:1
L/D Ratio18 – 22
Compression Ratio1 – 3
Tonnage Factor6.18 – 7.72kN/cm²
Thermal Diffusivity0.1548mm²/s
Max Shear Rate60,0001/s
Shrinkage0.8 – 3%
Regrind25%
Heat Deflection (HDT) @ 1.82 MPa252°C
Glass Transition (Tg) @ 10°C/min20°C
Vicat Softening @ 50N257°C

Drying

Drying Temperature79 – 91°C
Drying Time8 – 16h
Recommended Moisture0.15%
Recommended Dryer TypeDesiccant
Dew Point-40°C

Temperatures

Melt279 – 299°C
Nozzle271 – 304°C
Front277 – 310°C
Middle279 – 310°C
Rear271 – 310°C
Demolding57 – 91°C
Mold (Cooling)41 – 79°C
Feed Throat10 – 49°C

Processing

Back Pressure3.4 – 5.5bar
Screw Speed30 – 60RPM
Injection SpeedHigh
Barrel Occupancy20 – 70%
Injection Pressure350 – 1,400Pbar
Holding Pressure88 – 1,120Pbar
Cushion6.4 – 12.7mm

Mold

Runner Diameter3.05 – 6.1mm
Gate Diameter0.76 – 1.52mm
Gate Area0.46 – 1.82mm²
Wall Thickness0.76 – 4.57mm

Venting

Depth (Vent Depth)0.0254 – 0.0508mm
Land (Vent Land)0.508 – 1.52mm
Width (Vent / Clearance)4.06 – 12.7mm
Relief (Relief Channel)0.2032 – 0.4064mm

Frequently asked questions

PA66 is a semi-crystalline engineering thermoplastic in the polyamide family, synthesized by polycondensation of two monomers: hexamethylenediamine (HMDA, 6 carbons) + adipic acid (6 carbons) — hence the name 66. The alternating chain with amide groups (–CO–NH–) more symmetric than in PA6 allows higher crystallinity (50–60%) and denser packing. Density ~1.14 g/cm³ (1.40+ with 35% GF). Melting point 263°C (vs 220°C for PA6) — the key difference between the two.
PA66 wins on: HDT (255°C vs 220°C for PA6), stiffness, creep resistance under sustained load, better dimensional stability (absorbs less moisture, ~2.5% vs 3% for PA6 at equilibrium), automotive under-hood applications, continuous use temperature (110°C vs 90°C). PA6 wins on: toughness and impact (especially at low temperature), easier processing (melts at 220°C vs 263°C), better surface finish, cost (~15–25% cheaper). Rule of thumb: under-hood, high temperature, high load → PA66. Room-temperature mechanical parts with impacts, textiles, general brackets → PA6.
PA66 is hygroscopic (absorbs 2–3% ambient moisture) and very sensitive to hydrolysis at injection temperature (270–290°C). Moisture >0.15% reacts with the polymer chain → hydrolytic chain scission → loss of 30–40% impact, silver streaks, brittle parts, yellowish discoloration. Mandatory conditions: desiccant at 80–90°C for 4–6 h (never more than 90°C to avoid yellow oxidation), dew point ≤ –30°C, target ≤0.15% moisture. For PA66-GF, drying at 80°C is sufficient because the filler doesn't add more moisture.
Yes, no doubt. With 30–35% glass fiber, PA66 reaches: tensile strength 200+ MPa, modulus 11,000+ MPa, HDT 210–245°C, excellent creep resistance under sustained load (unlike POM or PBT, it doesn't slowly flow under prolonged load). Dominant applications: engine intake manifolds (replaced aluminum in the 90s, saved 50% weight), decorative engine covers with detail, acoustic resonators, structural engine brackets, oil/fuel filter housings, fuel line connectors (with HSHT grade — High Stiffness High Temperature). For EVs: inverter housings and battery packs are migrating to PA66-GF with FR (flame retardant).
Crisis 2018–2022: adiponitrile (ADN), the chemical precursor to make HMDA and by extension PA66, was produced by only 3 global manufacturers (Invista, BASF, Ascend). A series of force majeure events, accidents and technical problems collapsed global supply. Prices rose 200–300% in 2021–2022, automotive contracts broke, OEMs emergently migrated to PA6, PBT-GF or PA12. Today (2026): oversupply — China massively expanded ADN capacity, prices have fallen below historical. The shortage permanently changed the dynamic: there is now diversification of sources and many OEMs maintain alternative specs in PA6 or PBT to avoid sole-source dependency on PA66.
The PDS marks 41–79°C unfilled, 80–100°C for PA66-GF. Cold (41–60°C) = amorphous/partially crystalline parts that post-crystallize in storage = unstable dimensions. Hot (70–90°C unfilled, 90–110°C with GF) = full crystallization, final dimensions, better surface and achieved HDT. For critical mechanical parts and connectors: minimum 80°C, ideal 90–100°C. For engine covers with good finish: up to 110°C to reproduce textured detail.
Not by default — pure PA66 yellows and loses toughness under UV in a few months, just like PA6. For outdoor use you need grades with UV stabilizers (HALS + antioxidants) or the classic PA66 with carbon black (1.5–2.5% carbon black), which is the most UV-resistant. Standard outdoor applications: outdoor electrical connectors, handles, automotive mirrors, antennas → black stabilized PA66. For colors and outdoor simultaneously, PA66 grades with HALS + UV absorbers extend service life to 5–10 years.
Unfilled shrinkage 1.5–2.5% (similar to PA6), with GF35 reduced to 0.4–0.6%. But there's a post-mold phenomenon: the part absorbs ambient moisture and grows dimensionally 0.4–0.7% in the first 48–72 h until equilibrium. That's why many automotive OEMs specify pre-conditioning before measuring critical tolerances: immerse the part in 80°C water for 2–4 h, or leave it 72 h at 50% RH. This is critical in connectors that must form a hermetic seal on assembly (otherwise they jam) and in precision gears.
PA12 wins on: much lower moisture absorption (1.5% vs 2.5% for PA66), superior dimensional stability, chemical resistance to hydrocarbons, hydrolysis at high temperature. PA66 wins on: HDT, stiffness, cost (~30–50% cheaper than PA12), higher mechanical strength with GF, availability. Rule of thumb: general under-hood, high temperature → PA66-GF. Connectors submerged in fuel/oil for long periods, hydraulic lines, gas-station nozzles → PA12 (better hydrocarbon resistance and low absorption). Flexible fuel tubing → PA12 almost always. Structural under-hood housings → PA66-GF35.
The PDS marks 25% as recommended maximum. Each cycle slightly degrades molecular weight and increases hydrolysis sensitivity. For critical under-hood parts (where heat + humidity + fuel will stress the material), many OEMs limit to 10% or forbid regrind. Critical tip: PA66 regrind absorbs moisture from ambient air between operations faster than virgin because it has more exposed surface — always re-dry it 6–8 h before the next injection cycle. PA66 regrind storage in closed bag with desiccant is mandatory.

Sources

Discussion (0)