PA12 (Polyamide 12) Injection Moulding: Properties & Guide
PA12 (polyamide 12, nylon 12) is the polyamide of choice when dimensional stability in wet environments, fuel and hydraulic fluid resistance, and good toughness at low temperatures take priority over maximum stiffness or lowest cost. Its equilibrium moisture absorption at 50% RH — roughly 0.25%, compared to 2–3% for PA6 — is the defining property that sets it apart from every other nylon family. Nordmould processes PA12 in unfilled, glass-filled, flexible, and specialty compound forms through its manufacturing partner network.
What are the mechanical and thermal properties of PA12?
PA12 is a semi-crystalline polyamide. Its 12-carbon aliphatic chain reduces intermolecular hydrogen bonding — that structural fact is directly responsible for its low moisture uptake, lower melting point, and better low-temperature toughness compared with shorter-chain polyamides such as PA6 or PA66.
| Property | PA12 (dry) | PA12 (conditioned) | PA12 GF30 | Test Standard |
|---|---|---|---|---|
| Tensile Strength | 50–60 MPa | 45–55 MPa | 110–140 MPa | ISO 527 |
| Elongation at Break | 200–300% | 250–350% | 3–5% | ISO 527 |
| Flexural Modulus | 1,400–1,700 MPa | 1,100–1,400 MPa | 6,000–7,500 MPa | ISO 178 |
| Izod Impact (notched, 23°C) | 50–120 J/m | 80–200 J/m | 50–80 J/m | ISO 180 |
| Heat Deflection Temp (1.80 MPa) | 50–55°C | 45–52°C | 170–190°C | ISO 75 |
| Melting Point | 175–180°C | — | 175–180°C | DSC |
| Density | 1.01–1.03 g/cm³ | 1.01–1.03 g/cm³ | 1.20–1.30 g/cm³ | ISO 1183 |
| Mould Shrinkage | 0.8–1.5% | — | 0.4–0.7% | ISO 294-4 |
| Moisture Absorption (23°C / 50% RH) | ~0.25% | ~0.25% | ~0.15% | ISO 62 |
| Moisture Absorption (immersion, saturation) | ~1.5% | — | ~0.9% | ISO 62 |
The dry-to-conditioned property shift in PA12 is far smaller than for PA6 or PA66, where tensile strength and modulus can drop 30–50% at full conditioning. This stability is what makes PA12 the standard choice for precision parts used in humid or wet environments — dimensions taken off-tool are close to in-service dimensions.
Where is PA12 injection moulding used?
PA12's fuel resistance, low moisture sensitivity, and impact toughness at sub-zero temperatures have made it the preferred polyamide for demanding fluid-handling and precision mechanical applications — wherever a standard PA6 or PA66 part would swell, absorb moisture, or lose dimensional accuracy.
Automotive fuel systems: Quick-connect fittings, fuel line clips, vapour management valves, and fuel filter housings. PA12's fuel resistance and dimensional stability under temperature cycling are the key drivers.
Pneumatics and hydraulics: Tube fittings, push-in connectors, manifold bodies, and valve housings. PA12 maintains dimensional accuracy in wet air and hydraulic fluid environments where PA6 would swell.
Electrical connectors and cable management: Screened cable glands, connector housings, and cable ties requiring chemical and UV resistance. PA12's surface quality supports reliable pin retention dimensions.
Medical devices and diagnostics: Pump housings, tube connectors, and fluid-path components where sterilisability and dimensional consistency in aqueous environments are required.
Outdoor and marine hardware: Rope guides, pulley bodies, snap-hooks, and watercraft deck fittings where long-term dimensional stability in salt water or UV environments is specified.
Flexible and corrugated conduit fittings: Plasticised PA12 grades are overmoulded or moulded directly as flexible connectors for corrugated automotive conduit, combining the connector's structural rigidity with the conduit's flexibility.
What are the moulding characteristics of PA12?
PA12 is a moderate-to-easy material to process. Its low melt viscosity and moderate shrinkage make cavity filling straightforward; the relatively narrow melting range requires controlled barrel temperatures to avoid premature freeze-off or degradation near the gate.
Melt temperature: 220–260°C. The optimal range is 230–250°C for standard unfilled grades. Overheating above 270°C causes yellowing and molecular weight reduction. The melting point of PA12 (175–180°C) is lower than PA6 (215–220°C) or PA66 (255–265°C), which reduces energy consumption per cycle.
Mould temperature: 30–60°C. Higher mould temperatures improve crystallinity and surface quality; 40–50°C is typical for precision parts. Oil-heated moulds are preferred for large or thermally demanding geometries.
Drying: 4–6 hours at 80°C. PA12's low equilibrium moisture content means freshly opened bags are often close to moulding condition. Moisture-related splay and bubbles still occur with wet material and are eliminated by correct drying.
Injection pressure: 60–110 MPa. PA12 flows readily — particularly flexible grades — and fills thin sections efficiently.
Shrinkage: 0.8–1.5% unfilled; 0.4–0.7% for GF30 grades. Unlike PA6, PA12 undergoes negligible post-moulding hygroscopic growth, so parts produced from properly dried material are at or close to final dimensional state immediately after moulding.
Draft angles: 0.5–1.5° for smooth surfaces; 2° for textured walls.
Weld lines: PA12's good toughness means weld lines are less critical than in highly reinforced grades, but avoid weld lines in high-stress or flex-fatigue zones.
Which PA12 grades and variants should you consider?
| Grade / Variant | Key Property | Typical Use |
|---|---|---|
| Unfilled PA12 | Baseline toughness, dimensional stability | Connectors, fittings, precision parts |
| Flexible PA12 (plasticised) | Shore D 40–60, oil-resistant | Push-fit connectors, overmoulded conduit ends |
| PA12 GF10 | Moderate stiffness increase, low warpage | Precision structural parts |
| PA12 GF20 / GF30 | High stiffness, high HDT | Load-bearing structural components |
| PA12 carbon-filled (ESD/conductive) | ESD or fully conductive | Fuel-system EMC shielding, electronics |
| PA12 UV-stabilised | Outdoor durability | Marine, outdoor hardware |
| PA12 food / medical grade | Regulatory compliance | Fluid-path medical, food contact |
| PA12 heat-stabilised | Sustained 100°C service | Engine bay, industrial |
What are PA12's advantages and limitations?
Advantages:
- Equilibrium moisture absorption ~0.25% at 50% RH — the lowest of all commonly moulded polyamides; parts are dimensionally stable off the tool without pre-conditioning cycles
- Excellent resistance to petrol, diesel, aviation fuel, oils, and most hydraulic fluids
- Good toughness and impact resistance at low temperatures, down to −40°C for standard grades
- Flexible and rigid grades within the same polymer family, from rigid connectors to Shore D 40 plasticised overmould components
- Lower density than PA6 or PA66 (1.01–1.03 g/cm³ vs 1.12–1.15 g/cm³) — lighter parts at equivalent cross-section
Limitations:
- Higher material cost per kilogram than PA6, PA66, or PP-GF at comparable reinforcement levels
- Lower tensile strength and HDT than PA6/PA66 unreinforced — glass reinforcement is needed for structural applications above 60°C
- Attacked by strong acids, phenols, and concentrated halogenated solvents
- Limited UV resistance in standard grades; outdoor use requires UV-stabilised compounds
- Specialty grades (flexible, ESD, food-grade) carry longer supply chains and can extend project lead times
When should you choose PA12 over alternatives?
PA12 vs PA6: PA12 is the clear choice when the part operates in wet, humid, or fuel-contact conditions and dimensional stability without moisture conditioning is a hard requirement. PA6 wins on stiffness, tensile strength, and material cost when moisture management is acceptable.
PA12 vs PA66: PA12 handles fuel systems, sub-zero impact duty, and precision hydraulic fittings better. PA66 is correct for sustained temperatures above 150°C, heavy continuous structural loads, and applications where cost per unit of performance is the deciding criterion.
PA12 vs POM: PA12 for fuel resistance and low-temperature toughness; POM for precision sliding and bearing surfaces, tighter dimensional tolerances, and better creep resistance under sustained load.
PA12 vs PP-GF: PA12 is justified when fuel resistance, dimensional stability in water, or service above 100°C are required. Glass-filled PP delivers lower cost for structural applications that do not need those specific PA12 capabilities.
Recyclability and sustainability
PA12 is mechanically recyclable — in-process runners and sprues are reground and blended back at controlled ratios without significant property loss. Post-industrial recycled PA12 is commercially available in standard and glass-filled grades. Post-consumer recycled PA12 is limited in volume because the primary application sectors (automotive fuel systems, pneumatic connectors) have no systematic end-of-life collection. Recycled-content PA12 can be discussed for projects where lifecycle sustainability data is required for product reporting.
Frequently asked questions
How does PA12 differ from PA6 and PA66 in injection moulding?
PA12 absorbs roughly 0.25% moisture at 23°C/50% RH equilibrium, compared to 2–3% for PA6 and PA66 at the same conditions. In practice, this means PA12 parts are dimensionally stable without conditioning cycles, while PA6 parts continue to grow as they absorb moisture after moulding. PA12 also has a lower melting point, lower density, and better resistance to fuels and hydraulic fluids — at the cost of lower tensile strength and HDT.
Does PA12 need to be dried before injection moulding?
Yes, but less aggressively than PA6 or PA66. PA12 should be dried at 80°C for 4–6 hours before moulding. Its low equilibrium moisture content means that correctly stored material is closer to the dry-as-moulded state than other polyamides, reducing sensitivity to storage conditions.
What is the shrinkage rate of PA12 in injection moulding?
PA12 shrinks 0.8–1.5%, broadly similar to PA66 and at the lower end of PA6's range (0.8–2.0%). The more important point is post-moulding growth: PA6 continues to expand as it absorbs moisture from the environment, adding up to 0.3% or more to critical dimensions over weeks. PA12 undergoes negligible hygroscopic growth, so the as-moulded dimensions are the final dimensions.
Is PA12 suitable for fuel system components?
Yes. PA12 has excellent resistance to petrol, diesel, aviation fuel, and most hydraulic fluids, which is why it dominates automotive fuel line connectors, quick-connect fittings, and vapour management components. Barrier grades and glass-filled variants are used for structural fuel system housings.
Can PA12 be used in flexible injection-moulded parts?
Flexible PA12 grades (plasticised polyamide 12) combine PA12's chemical resistance with rubber-like compliance, achieving Shore D 40–60. They are used in push-fit tubing connectors, over-moulded cable jacketing, and corrugated flexible conduit connectors where flexibility and fuel or oil resistance are both needed.
What are the main limitations of PA12 compared to other polyamides?
PA12 has lower tensile strength and heat deflection temperature than PA6 or PA66 at equivalent wall thickness. It is also more expensive per kilogram. Glass-filled PA12 closes most of the stiffness gap, but for applications above 150°C or under sustained heavy structural load, PA66 or PA46 is the better choice.
Is PA12 available in glass-filled grades for injection moulding?
Yes. PA12 GF10, GF20, and GF30 grades are commercially available from major compounders. GF30 PA12 achieves a flexural modulus of approximately 6,000–7,500 MPa and an HDT typically in the range of 150–185°C depending on grade and test load — confirm the specific value with the datasheet for your chosen compound. The key advantage over GF-PA6 is retained: PA12's dimensional stability in wet and fuel environments carries through to the reinforced grades. Reinforced PA12 grades for structural parts with low moisture sensitivity can be sourced through the partner network.
What surface finishes are possible on PA12 injection-moulded parts?
PA12 produces a smooth, semi-gloss surface from a well-polished tool, and takes texture well. It can be painted or laser-marked. Like other nylons, PA12 has low surface energy, so flame or plasma activation is required before adhesive bonding or painting. Matt, gloss, and textured surface finishes are achievable depending on tool specification.
Send your PA12 part design for a free DFM review — grade selection, tooling recommendations, and a written quote typically returned within one business day.