PETG and nylon both make tough, functional parts, but they sit at different levels of effort. Prusa describes PETG as easy to print and suitable for beginners, and nylon as very hard to print and recommended for experienced users. The reasons are moisture, warping and temperature: nylon absorbs water quickly, and its properties change as it does.
This page compares Polymaker PolyLite PETG with Polymaker PolyMide CoPA, a copolymer nylon, using the same supplier's ISO test data. Polymaker reports CoPA both dry and after soaking in water, which shows the range a nylon part can move through in service. Prusa's guides add printing and safety notes. Other nylons, such as PA12 or fiber-filled grades, behave differently.
PETG and Nylon / polyamide side by side
| Property | PETG | Nylon / polyamide |
|---|---|---|
| Nozzle temperature | 230–260 °C (PolyLite PETG); Prusa: 230 °C first layer, 240 °C after | 250–270 °C (PolyMide CoPA); Prusa: 285 °C |
| Bed temperature | 70–80 °C (PolyLite PETG); Prusa: 85 °C first layer, 90 °C after | 25–50 °C (PolyMide CoPA); Prusa: 110 °C |
| Enclosure | Not needed (Polymaker) | Needed, ambient temperature (Polymaker); Prusa: high ambient temperature helps a lot with warping |
| Build surface | PC or textured PEI, glue when needed (Polymaker); Prusa: not on smooth PEI | PC or textured PEI, glue when needed (Polymaker); Prusa: PA Nylon sheet |
| Moisture handling | Polymaker: print from its PolyBox and store in the resealable bag | Polymaker: store and use below 20% RH; Prusa: can absorb up to 10% of its weight in water |
| Drying | 65 °C for 6 h (Polymaker) | 100 °C for 8 h (Polymaker); Prusa: at least 4 h below 90 °C |
| Heat deflection, ISO 75 (1.8 / 0.45 MPa) | 75 °C / 78 °C | 70 °C / 111 °C |
| Tensile strength, ISO 527 (X-Y / Z) | 50.8 / 42.8 MPa | Dry: 78.0 / 45.8 MPa; wet: 34.3 / 13.7 MPa |
| Tensile modulus, ISO 527 (X-Y) | 2116.8 MPa | Dry: 2703 MPa; wet: 724 MPa |
| Elongation at break (X-Y / Z) | 8.4% / 3.3% | Dry: 12.7% / 1.3%; wet: 13.2% / 1.7% |
| Notched Charpy impact, ISO 179 (X-Y) | 2.6 kJ/m² | Dry: 6.9 kJ/m²; wet: 27.7 kJ/m² |
| Annealing | Not stated | 80 °C for 6 h (Polymaker) |
| Fumes | Not stated | Prusa: strong odor and potentially dangerous ultrafine particles; ventilated room or enclosure |
Property values come from Polymaker's PolyLite PETG and PolyMide CoPA technical data sheets (ISO methods, 100% infill specimens; CoPA reported dry and after 48 hours in 60 °C water), with printing and safety guidance from Prusa's PETG and polyamide articles.
Moisture is the big difference
Polymaker tested PolyMide CoPA dry and again after 48 hours in 60 °C water, which left the bars at an average 6.16% moisture. Soaking cut the tensile modulus from 2,703 MPa to 724 MPa and in-plane tensile strength from 78.0 MPa to 34.3 MPa, while notched Charpy impact rose from 6.9 to 27.7 kJ/m². Parts in ordinary room air will usually sit somewhere between those two states; Polymaker does not report an in-between value.
PolyLite PETG has one set of values, and Prusa lists water and humidity resistance among PETG's strengths. Both filaments still benefit from dry storage: Polymaker recommends drying PETG at 65 °C for 6 hours, against 100 °C for 8 hours for CoPA, and says CoPA should be stored and used below 20% relative humidity. Prusa says nylon can absorb water up to 10% of its weight, and that wet nylon bubbles and prints with a poor surface.
Strength, stiffness and impact
Dry, CoPA is the stronger material in the print plane (78.0 MPa against 50.8 MPa for PETG) and slightly stiffer. Across layers the two are close when dry, at 45.8 MPa for CoPA and 42.8 MPa for PETG, but wet CoPA drops to 13.7 MPa in the Z direction.
Impact tells a clearer story. CoPA's notched Charpy value is higher than PETG's 2.6 kJ/m² in both states, at 6.9 kJ/m² dry and 27.7 kJ/m² wet. Prusa describes nylon as tough in large volumes and flexible in thin layers, with a low coefficient of friction, which is why it shows up in gears and bendable parts.
Heat
Under the 1.8 MPa ISO 75 load the two are similar: 75 °C for PolyLite PETG and 70 °C for PolyMide CoPA. Under the lighter 0.45 MPa load, CoPA reaches 111 °C against PETG's 78 °C. A nylon part under light load therefore copes with more heat, while a rigid, heavily loaded part gains little by switching.
Prusa says PETG suits most exterior uses at temperatures below 80 °C, and lists high-temperature resistance among nylon's strengths.
Printing effort and fumes
PETG prints on an open printer: Polymaker lists no enclosure, with the part-cooling fan from off to 20%. Prusa's main cautions are stringing, weak bridges and overhangs, and adhesion so strong that it can damage a smooth PEI sheet. Nylon is more demanding. Polymaker lists an enclosure for CoPA, Prusa says nylon is prone to warping and recommends its PA Nylon sheet, and Polymaker recommends annealing CoPA parts at 80 °C for 6 hours.
Prusa warns that polyamides give off a strong odor and potentially dangerous ultrafine particles and says to print them in a well-ventilated room or an enclosure. Its PETG article does not discuss fumes.
Which should you choose?
Choose PETG if…
- You want a functional part without an enclosure or a special build sheet.
- The part lives outdoors or near water below the 80 °C limit Prusa gives for most PETG exterior use.
- Stiffness should stay steady whatever the humidity.
- You cannot keep filament below the 20% relative humidity Polymaker asks for with CoPA.
Choose Nylon / polyamide if…
- The part slides or wears, such as a gear, where Prusa credits nylon with low friction.
- The part must absorb impacts; CoPA's notched Charpy value beats PETG's dry and wet.
- Thin sections should flex rather than crack, which Prusa lists among nylon's strengths.
- You can dry filament at 100 °C, print in an enclosure and ventilate the room.
Common questions
Is nylon stronger than PETG?
Dry, yes in the print plane: Polymaker lists 78.0 MPa for PolyMide CoPA against 50.8 MPa for PolyLite PETG. After water soaking, CoPA drops to 34.3 MPa, below PETG. CoPA's impact strength is higher than PETG's in both states.
Does PETG need drying like nylon?
Both benefit from dry filament, but nylon is far more demanding. Polymaker lists 65 °C for 6 hours for PolyLite PETG and 100 °C for 8 hours for CoPA, and asks for CoPA to be stored and used below 20% relative humidity. Prusa says nylon can absorb up to 10% of its weight in water.
Can nylon be printed on an open-frame printer?
Polymaker lists an enclosure as needed for CoPA, and Prusa says high ambient temperature helps a lot with warping. Prusa notes that carbon-fiber-filled grades warp much less. Ventilation still matters, because Prusa warns of ultrafine particles from polyamides.
Sources
- PolyLite PETG technical data sheet Polymaker · Checked 2026-11-02
- PolyMide CoPA technical data sheet Polymaker · Checked 2026-11-02
- PETG Prusa Research · Checked 2026-10-15
- Polyamide (Nylon) Prusa Research · Checked 2026-10-15
This comparison summarizes the cited documentation; it is not a lab test. Properties vary by brand, grade, print settings and orientation, so check the data sheet for the exact product you buy.