Material selection
Nylon vs PEEK
Nylon is the default engineering thermoplastic; PEEK is the upgrade when service temperature or chemical exposure goes past what nylon can survive. The two are not close on price, so the question worth answering first is whether the part actually needs PEEK, or whether it has been specified out of caution rather than requirement. The numbers below are the same published values used on each material's own page, set side by side.
| Nylon (PA6) | PEEK | |
|---|---|---|
| Density | 1.13 g/cm³ | 1.30 g/cm³ |
| Tensile strength | 70–85 MPa (dry) | 95–100 MPa |
| Flexural modulus | 2.7 GPa (dry) | 3.9 GPa |
| Heat performance | 70 °C HDT unfilled, 220 °C GF30 | 250 °C continuous service, 343 °C melting point |
| Water absorption | 2.5–3.5 % at saturation | 0.1 % |
| Relative cost | Medium | Very high |
Published values for unfilled grades at 23 °C unless stated, taken from each material's own datasheet page. Nylon's heat figure is a deflection temperature under load, PEEK's is a continuous-use rating; the two are different measures and are not directly interchangeable. Confirm against the supplier datasheet for the grade you specify.
What Nylon (PA) is
Nylon is the workhorse engineering thermoplastic: high strength, high toughness, and excellent abrasion resistance, with glass-filled grades reaching stiffness and heat resistance that put them in direct competition with die-cast aluminum. The property to design around is moisture: nylon absorbs 2 to 3 percent water at equilibrium, which swells the part, softens it, and roughly doubles its impact strength, so published dry-as-molded data does not describe the part in service. Its practical ceiling is well short of PEEK's: even glass-filled grades are rated for continuous service in the low hundreds of degrees Celsius, not 250 °C.
What PEEK is
PEEK is a semi-crystalline aromatic polymer that keeps useful mechanical properties to 250 °C continuously, resists almost all chemicals except concentrated sulphuric acid, and survives repeated steam sterilization without degrading. Material cost is roughly a hundred times ABS, so it is specified when a metal part needs to be lighter, non-conductive, or radiolucent and nothing cheaper will survive the environment, not as a default upgrade from nylon.
Nylon against PEEK
| Nylon (PA6) | PEEK | |
|---|---|---|
| Heat ceiling | 70 °C HDT unfilled, up to 220 °C HDT in GF30 grades; softens well before PEEK's range | 250 °C continuous service, 343 °C melting point, the reason it gets specified over nylon in the first place |
| Chemical and sterilization resistance | Good against fuels, oils and greases; not rated for repeated steam autoclave cycles | Resists almost all chemicals except concentrated sulphuric acid and survives repeated steam sterilization without degrading |
| Moisture behaviour | Absorbs 2 to 3 percent water at saturation, which swells and softens the part; dimensions must be sized for the conditioned state, not as-molded | 0.1 percent water absorption, effectively dimensionally stable regardless of humidity |
| Processing | Dry below 0.15 percent moisture, melt 240 to 295 °C depending on grade; runs on a standard injection molding cell | Dry 3 hours at 150 °C, melt 360 to 400 °C, mold 175 to 205 °C; needs a high-temperature machine and a heated tool, not a standard cell |
| Relative cost | Medium, the default choice when its envelope is sufficient | Very high, roughly a hundred times ABS; the cost has to be justified by the requirement, not assumed |
Which one, for which part
- Structural brackets, gears, housings and cable management within roughly 100 °C service and no aggressive chemical or steam exposure is nylon's case, usually a glass-filled grade: adequate stiffness and heat resistance at a fraction of PEEK's cost.
- Parts that see continuous service near or above 200 °C, or repeated steam autoclave cycles is PEEK's case: nylon's glass-filled ceiling does not reach that range and its moisture uptake makes autoclave cycling unreliable.
- Radiolucent or implantable medical components needing ISO 10993 documentation favour PEEK, which has implantable grades with full documentation; nylon has no equivalent offering here.
- Dry-running bearings and low-friction wear parts at moderate temperature usually stay with nylon's MoS₂- or PTFE-filled grades, which cost a fraction of PEEK's own bearing grade for a similar service life below PEEK's heat range.
- Any part where "PEEK to be safe" is the only reason on the drawing is worth re-checking against nylon GF30 first: the temperature and chemical ceiling most parts actually see sits inside nylon's range, and the saving is roughly two orders of magnitude in material cost.
Our status
Trumould molds both nylon and PEEK in-house through injection molding; PEEK runs on our high-temperature-capable presses with a heated tool, which not every job shop supports. CNC machining and 3D printing are available for both materials. Send the part, its service temperature, chemical or sterilization exposure, and target volume, and the quote states whether nylon is sufficient or PEEK is actually required, not just a price for whichever one you asked about first.
Specifying this part?
Send your CAD and target volumes. We come back with a price, a lead time, and any material or design notes that would reduce either.