Nylon Injection Moulding: PA6 and PA66 Material Guide
Nylon (polyamide) is one of the most widely used engineering thermoplastics in injection moulding. PA6 and PA66 deliver a combination of high tensile strength, good fatigue resistance, low friction, and broad chemical resistance that few commodity plastics can match. Both grades are available at Nordmould for low-to-mid volume series from 100 pieces.
What are the key mechanical and thermal properties of PA6 and PA66?
Polyamide grades vary meaningfully in their mechanical and thermal performance. The table below lists standard industry values for unfilled and glass-filled variants — the most common choice set for structural parts.
| Property | PA6 (unfilled) | PA66 (unfilled) | PA66-GF30 |
|---|---|---|---|
| Tensile strength (dry) | 70–85 MPa | 80–90 MPa | 170–195 MPa |
| Flexural modulus (dry) | 2,700–3,200 MPa | 3,000–3,500 MPa | 9,000–11,000 MPa |
| Elongation at break | 30–150 % | 20–80 % | 2–5 % |
| Notched Izod impact | 5–7 kJ/m² | 4–6 kJ/m² | 9–12 kJ/m² |
| Heat deflection temp (1.8 MPa) | 55–65 °C | 70–80 °C | 240–255 °C |
| Continuous use temp | 85–100 °C | 100–115 °C | up to 150 °C |
| Water absorption (24 h) | 1.3–1.6 % | 1.0–1.3 % | 0.7–1.0 % |
| Density | 1.13–1.15 g/cm³ | 1.14–1.16 g/cm³ | 1.35–1.38 g/cm³ |
Note: properties are measured on dry-as-moulded (DAM) specimens. Conditioned (equilibrium moisture) values for tensile strength drop 20–30 % and impact strength rises substantially — relevant for outdoor or humid-environment parts.
What are the typical applications of nylon injection moulding?
Nylon's combination of stiffness, fatigue resistance, and low coefficient of friction makes it the default engineering plastic for moving or load-bearing components.
Automotive and under-bonnet: intake manifolds, radiator end tanks, cable ties, clips, bearing cages, and gear wheels all commonly use PA66 or PA66-GF30 for heat resistance above 100 °C.
Electrical and electronics: nylon's UL 94 flame-retardant grades are widely specified for connectors, circuit-breaker housings, and cable management. PA6 is common here because of its easier flow into thin walls.
Industrial machinery: wear pads, bushings, sprockets, and conveyor components exploit nylon's self-lubricating surface and resistance to oils, greases, and fuels.
Consumer products: sports equipment buckles, ski bindings, and power-tool housings use PA66 for impact absorption combined with stiffness.
How is nylon processed in injection moulding?
Nylon's low melt viscosity means it flows well but also flashes easily if tooling clearances are generous. Good tool maintenance and tight vent dimensions are important.
| Processing parameter | PA6 | PA66 |
|---|---|---|
| Melt temperature | 230–260 °C | 270–290 °C |
| Mould temperature | 60–80 °C | 70–90 °C |
| Injection pressure | 80–130 MPa | 80–140 MPa |
| Shrinkage (unfilled) | 1.0–2.0 % | 0.8–1.8 % |
| Shrinkage (GF30) | 0.3–0.8 % | 0.3–0.7 % |
| Recommended draft angle | ≥ 0.5° per side | ≥ 0.5° per side |
Sink marks and warp: wall thickness variation is the primary sink driver. Keep walls between 1.5–3.5 mm and transitions gradual (< 25 % step change) to minimise sink. In glass-filled grades, gate location controls fibre orientation and, therefore, the direction of differential shrinkage; off-centre gating on flat parts almost always produces warp.
Gate design: submarine, pin-point, and fan gates all work well. For thin-wall PA66 parts, hot-runner systems improve fill consistency and reduce material waste.
Moisture management: nylon must be dried immediately before moulding (see FAQ). Parts should be stored in sealed bags with desiccant if assembled weeks after moulding, as post-moulding moisture uptake changes dimensions slightly.
What grades and variants are available?
| Grade | Key feature | Typical use case |
|---|---|---|
| PA6 natural | Low cost, good flow | Connectors, general-purpose parts |
| PA66 natural | Higher heat & stiffness | Automotive, structural clips |
| PA66-GF15 | Moderate reinforcement, better surface vs GF30 | Enclosures needing stiffness |
| PA66-GF30 | High stiffness, low shrinkage | Structural brackets, motor covers |
| PA66-GF50 | Maximum stiffness | Load-bearing structural parts |
| PA6 FR (UL94 V-0) | Flame retardant | Electrical connectors, switchgear |
| PA12 | Low moisture uptake, flexibility | Fuel lines, tubing, outdoor parts |
| PA6-MoS₂ | Improved lubrication | Gears, bearings, sliding parts |
Engineering-grade resins beyond this list — including heat-stabilised, impact-modified, and carbon-fibre-filled polyamides — can be sourced on request through Nordmould's material partner network.
What are the advantages and limitations of nylon?
Advantages:
- High strength-to-weight ratio compared with metals and many other plastics
- Excellent fatigue resistance under cyclic loading
- Low friction coefficient; self-lubricating in unfilled form
- Good resistance to oils, fuels, alkalis, and most organic solvents
- Wide range of reinforced and functional grades available
- Cost-effective for mid-volume series once tooling is amortised
Limitations:
- Hygroscopic: moisture uptake changes dimensions and reduces stiffness — relevant for precision parts in humid environments
- Higher mould temperatures needed than commodity plastics — slightly longer cycle times
- Glass-filled grades are abrasive on tooling, requiring hardened steel for long runs
- Not well suited to strong acids or oxidising agents
- Difficult to bond with standard adhesives without surface treatment
When should you choose nylon over alternative materials?
Choose nylon over PP when the part operates above 80 °C, carries structural load, or needs low friction. PP is cheaper and moisture-insensitive, but its lower stiffness and creep resistance make it unsuitable for load-bearing applications.
Choose nylon over POM when you need glass-fibre reinforcement, lower cost at equivalent stiffness, or better impact resistance. POM edges out unfilled nylon on dimensional stability in humid environments — nylon absorbs more water and expands slightly.
Choose PA66-GF30 over aluminium for weight reduction on structural brackets where operating temperature stays below 150 °C. The stiffness-to-density ratio is competitive and tooling costs far less than metal machining for volumes above a few thousand pieces.
Choose PA12 over PA6/PA66 for outdoor or humid applications where dimensional stability under moisture is critical, such as fluid-line fittings or outdoor sensor housings.
Recyclability and sustainability
Nylon is technically recyclable (resin code 7 or product-specific), and post-industrial PA6/PA66 regrind is widely reprocessed into lower-grade applications such as carpet fibre and moulded consumer goods. In injection moulding, sprue and runner regrind can typically be blended back at 10–20 % without significant property loss in non-critical applications. Bio-based PA grades (e.g. PA6.10 from castor oil) are available as a lower-carbon-footprint alternative; Nordmould can source these on request.
Send Nordmould your STEP file for a free DFM review — we'll confirm grade suitability, flag any warp or sink risks, and return a written quote within one business day.
Frequently asked questions
What is the difference between PA6 and PA66 for injection moulding?
PA6 (polycaprolactam) has a lower melting point (~220 °C), absorbs more moisture, and flows more easily — making it cheaper to process. PA66 (polyhexamethylene adipamide) melts at ~260 °C, offers higher stiffness and better heat resistance. Nordmould supplies both grades; PA66 is recommended for under-bonnet or high-load applications.
Does nylon warp badly in injection moulding?
Nylon shrinks 1.0–2.5 % (unfilled) and is highly directional in glass-filled grades, which creates warp risk on asymmetric parts. Nordmould's DFM review checks wall uniformity, gate placement, and whether a glass-filled or mineral-filled grade would reduce warpage for your geometry.
Can nylon be used in food-contact or medical applications?
Food-contact grades of PA6 and PA66 are available; FDA/EU 10/2011-compliant resins can be sourced on request. For medical applications, Nordmould can specify biocompatible polyamide grades — confirm requirements during the DFM review so the correct resin and processing documentation are arranged.
What are glass-filled nylon grades used for?
Glass-filled nylon (e.g. PA66-GF30 = 30 % short glass fibre) roughly doubles tensile strength and halves shrinkage compared with unfilled nylon, at the cost of increased surface roughness and brittleness. Nordmould recommends GF grades for structural brackets, motor housings, and load-bearing clips.
How much does nylon tooling cost at Nordmould?
Nylon tooling starts from €3,000 for simple bridge tools, with production steel tooling priced depending on part complexity and cavity count. Nylon is abrasive in glass-filled form, so hardened steel tooling is recommended for series of tens of thousands of parts.
Does nylon require drying before moulding?
Yes. Nylon is hygroscopic and must be dried to under 0.2 % moisture before processing — typically 4–8 hours at 80 °C for PA6 and 4 hours at 85 °C for PA66. Inadequate drying causes splay, blistering, and a significant drop in mechanical properties. Nordmould's process controls include resin pre-drying as standard.
What surface finishes are available for nylon parts?
Unfilled nylon takes matt and semi-gloss finishes well. High-gloss finishes are achievable on unfilled grades with polished tooling but are rarely specified because nylon's natural moisture absorption gradually dulls optical surfaces in service. Glass-filled grades are limited to matt or textured finishes due to fibre read-through.