Both PETG and ASA are common picks for parts that leave the house: garden fixtures, mounts, covers and enclosures. PETG prints on an open machine and handles water well. ASA was developed for weather exposure and is rated by Prusa for high UV resistance, but it prints hotter, warps more and gives off fumes.
The numbers on this page come from one supplier, Polymaker, whose PolyLite PETG and PolyLite ASA data sheets use the same ISO test methods. Prusa's material guides add printing, outdoor and safety notes. Check the data sheet for your own spool, because grades and colors vary.
PETG and ASA side by side
| Property | PETG | ASA |
|---|---|---|
| Nozzle temperature | 230–260 °C (PolyLite PETG); Prusa: 230 °C first layer, 240 °C after | 230–260 °C (PolyLite ASA); Prusa: 260 °C |
| Bed temperature | 70–80 °C (PolyLite PETG); Prusa: 85 °C first layer, 90 °C after | 75–95 °C (PolyLite ASA); Prusa: 105 °C first layer, 110 °C after |
| Enclosure | Not needed (Polymaker; Prusa enclosure guide) | Needed (Polymaker); Prusa says needed for large parts |
| Heat deflection, ISO 75 (1.8 / 0.45 MPa) | 75 °C / 78 °C | 100 °C / 103 °C |
| Tensile strength, ISO 527 (X-Y / Z) | 50.8 / 42.8 MPa | 43.8 / 32 MPa |
| Tensile modulus, ISO 527 (X-Y) | 2116.8 MPa | 2379 MPa |
| Elongation at break (X-Y / Z) | 8.4% / 3.3% | 6.7% / 1.65% |
| Notched Charpy impact, ISO 179 (X-Y) | 2.6 kJ/m² | 10.3 kJ/m² |
| UV and outdoor use | Prusa: suitable for most exterior use below 80 °C; UV resistance not stated | Prusa: high UV resistance, temperature resistance up to 93 °C |
| Fumes and ventilation | Not stated in Prusa's PETG article | Prusa: potentially dangerous styrene fumes; print in a well-ventilated area |
| Drying | 65 °C for 6 h (Polymaker); Prusa lists 55 °C for 6 h for Prusament PETG | 70 °C for 7 h (Polymaker); Prusa lists 80 °C for 4 h for Prusament ASA |
| Typical uses | Prusa: mechanical parts indoors and out, holders, clamps, waterproof parts, boxes | Prusa: outdoor and technical parts, UV-resistant outdoor parts, fan shrouds |
Property values come from Polymaker's PolyLite PETG and PolyLite ASA technical data sheets (same ISO test methods, 100% infill specimens), with printing, UV and safety guidance from Prusa's PETG, ASA, drying and enclosure articles.
Outdoor exposure
Prusa lists high UV resistance as one of ASA's main strengths and recommends it for outdoor use. Polymaker describes PolyLite ASA as having improved weather resistance compared with ABS. Prusa's PETG article says PETG parts are suitable for most exterior uses below 80 °C and lists water and humidity resistance among its strengths, but it does not rate PETG's UV resistance.
Neither supplier publishes weathering test figures in these data sheets. For a part that will sit in direct sun for years, the stated UV resistance favors ASA. For a part that is mostly shaded or wet, PETG may be enough, and a test piece left in the actual location is a practical check.
Heat and mechanical data
Polymaker lists heat deflection temperatures of 75 °C for PolyLite PETG and 100 °C for PolyLite ASA under the 1.8 MPa load. That 25-degree gap is worth weighing against the part's expected temperature and load.
The mechanical data split. PETG has the higher tensile strength, 50.8 MPa in-plane and 42.8 MPa across layers, against 43.8 MPa and 32 MPa for ASA. ASA is slightly stiffer and its notched Charpy value is 10.3 kJ/m² against 2.6 kJ/m² for PETG. Polymaker presents these values for reference and comparison rather than design, so test the real part in the orientation it will be printed.
Printing and the room
PETG prints on an open-frame printer; Prusa's enclosure guide groups it with PLA as a low-shrinkage filament. It does need the right sheet, since Prusa warns that PETG can damage smooth PEI.
ASA needs a hotter bed, a warm environment and ventilation. Prusa lists significant warping as ASA's main drawback, says an enclosure is needed for large parts, and warns of potentially dangerous styrene fumes. Polymaker lists an enclosure as needed for PolyLite ASA at any size. If the printer is in a living space without an enclosure or ventilation, that alone may decide the choice.
Moisture and finishing
Polymaker recommends drying PolyLite PETG at 65 °C for 6 hours and PolyLite ASA at 70 °C for 7 hours. Prusa's drying table gives different figures for its own Prusament grades, so use the guidance for your brand. ASA can be smoothed and glued with acetone, according to Prusa, while smoothing PETG needs dichloromethane, which Prusa reserves for trained lab staff.
Which should you choose?
Choose PETG if…
- The printer has no enclosure, or the room has limited ventilation.
- The part sees water or humidity and stays below about 80 °C, as Prusa describes.
- Steady tension matters, given PolyLite PETG's higher tensile strength.
- You want a functional part with less warping risk on large prints.
Choose ASA if…
- The part will spend long periods in direct sunlight, where Prusa rates ASA's UV resistance highly.
- The part may run warmer than PETG's range, toward the 100 °C heat deflection temperature Polymaker lists for PolyLite ASA.
- The part may be knocked, given ASA's higher notched impact value in the PolyLite data.
- You have an enclosed, ventilated setup and want acetone smoothing.
Common questions
Is PETG good enough for outdoor parts?
Prusa says PETG suits most exterior uses below 80 °C, but its PETG article does not rate UV resistance. Prusa does rate ASA for high UV resistance, which makes ASA the better-documented option for long sun exposure.
Which is easier to print?
PETG. Polymaker lists no enclosure for PolyLite PETG but lists one as needed for PolyLite ASA, and Prusa notes ASA warps significantly and releases styrene fumes.
Which is stronger?
In Polymaker's data, PETG has higher tensile strength and ASA has a higher notched impact value and slightly higher stiffness. The right choice depends on how the part is loaded.
Sources
- PolyLite PETG technical data sheet Polymaker · Checked 2026-11-02
- PolyLite ASA technical data sheet Polymaker · Checked 2026-11-02
- PETG Prusa Research · Checked 2026-10-15
- ASA Prusa Research · Checked 2026-10-15
- Drying filament Prusa Research · Checked 2026-10-15
- Enclosure guidepost Prusa Research · Checked 2026-10-16
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.