Filament for sun-exposed parts: separating heat and UV resistance

Describe UV and thermal requirements separately

For an outdoor part, record UV exposure separately from the temperature at which it may operate. The sources reviewed do not describe a universal degradation path for every polymer, color or geometry. They also do not give the temperature reached by a dark part in every situation. First define use, load, intended exposure period and measurable conditions at the installation.

The two sheets answer the two questions differently. Prusament makes a qualitative statement about UV stability of its ASA and gives a temperature-resistance figure without a published test method on the page. Polymaker PETG provides thermal values with stated methods and loads but no UV data in its TDS. Tg, Vicat and HDT are different measurements; they are not interchangeable and do not by themselves give a use limit for your part.

What the Prusament ASA page actually documents

The Prusament ASA page describes the grade as UV stable, suitable for long-term outdoor use, and says it will not turn yellow. This is a manufacturer statement about its ASA; the page does not provide an exposure duration, irradiance or weathering curve here. It also lists temperature resistance up to 93 °C and reports no signs of deformation at temperatures near that value, without stating the method or load. Do not convert that figure into a guaranteed service temperature.

For printing this grade, Prusa lists a 110 ± 5 °C bed, 260 ± 5 °C nozzle, 30% part cooling and recommends an enclosure or tall skirt. The page rates warping susceptibility high and calls ASA hygroscopic; it also notes styrene content and odor during printing. These are printing details for the Prusament ASA shown, to check against your machine’s capabilities and instructions. The ABS and ASA page provides broader context about these materials. These statements are specific to the named Prusament ASA grade. They do not prove that a particular part will retain its dimensions or properties outdoors for a specified period. For a demanding requirement, seek documentation matching the grade, geometry, load and intended exposure conditions.

What the Polymaker PETG data sheet measures, and what it leaves out

The Polymaker PETG TDS lists several thermal measurements with methods: Tg 71.24 °C by DSC, Vicat 75 °C per ISO 306, and HDT 69 °C at 0.45 MPa and 65 °C at 1.8 MPa per ISO 75. These values are tied to their methods and test conditions. They do not predict how hot a part will get in the sun and are not guaranteed service temperatures.

The Polymaker PETG TDS gives no UV-resistance value or yellowing measurement. That does not support a conclusion either way about its UV performance. Its disclaimer says typical values are for reference and comparison, should not be used as design specifications, and may vary with printing conditions, part design and environment. The TDS settings include “Closure chamber: Not Needed” and stated nozzle and bed temperatures for this product; check the full sheet before applying them.

The PETG filament page does not replace the named grade’s TDS. To decide, record the expected temperature in your installation and look for data matching the material, grade and load. Do not directly compare a Prusa figure with no stated method or load to a Polymaker HDT tested under ISO 75. A lab value can frame questions, but these documents are not enough to qualify a specific part as safe at a given temperature.

A use-case matrix based on how your part is really exposed

Start by describing actual exposure: direct UV or shade, intended duration, measured or required temperature, mechanical load, and exact material color/reference. For UV, the Prusament ASA page makes a stability statement for that grade; the Polymaker PETG TDS does not address the variable. This difference in documentation does not by itself demonstrate material superiority or the performance of the final part.

For heat, note the stated methods and loads rather than treating Tg, Vicat, HDT and Prusa’s 93 °C statement as one scale. The Polymaker value of 65 °C at 1.8 MPa is an HDT result under ISO 75; it does not automatically reproduce a screw clamp or an assembly geometry. If those stresses matter, seek data or tests matching the actual assembly and load, without turning the cited numbers into an ASA/PETG ranking. The Prusament ASA page also describes printing constraints: high warping susceptibility, hot bed and nozzle, fan and recommended enclosure or skirt. Check these requirements against your printer and part size. For another material or grade, use its own documentation. The 3D printer enclosure guide can explain the setup without guaranteeing a result for a particular geometry.

Reading a datasheet without confusing lab tests with sun aging

The Polymaker TDS describes how its specimens were made: printing at 240 °C, 80 °C bed, 100% infill, two shells, fan off and ambient temperature. It says the HDT curve averages three samples and warns actual values may vary. These conditions help interpret this sheet’s results; they do not automatically reproduce your part or its environment.

The Prusament ASA page makes a qualitative UV statement but gives no exposure duration, irradiance or measured loss after weathering. The PETG TDS does not address UV. If your own specification calls for observation under real conditions, you can monitor a witness sample at the intended location; that personal procedure does not turn these sources into a lifetime guarantee or standardized test. For any part, record the exact grade and color, cited test method, load and exposure conditions. The two documents do not characterize every color or grade in these families. A statement about one Prusament ASA product does not automatically transfer to another product, and the Polymaker PETG TDS does not document UV performance.

Printing, drying, and finishing parts headed outdoors

For the Prusament ASA shown, the page recommends a satin sheet, warns adhesion can be too strong on certain other sheets, and advises allowing the part to cool before removal. It names an enclosure or tall skirt as options against warping. The Polymaker PETG TDS lists a 60–70 °C bed, PC or textured PEI surface, and “Closure chamber: Not Needed” for that product. These instructions apply to the named grades; check your machine and current sheet before printing.

Prusament calls its ASA hygroscopic. The Polymaker PETG TDS shows a water-absorption curve, a “Max Water Absorption Rate 0.51%” note associated with a curve at 70% RH and 23°C, and drying at 55 °C for six hours; it also recommends a dry box for printing or storage. Apply those details to the product described and record spool condition. The sources do not establish a service life for an outdoor part based on whether its filament is dry or wet. The Prusament page says this ASA can be wet- or dry-sanded and smoothed with acetone vapor, with some fine detail lost and sharp edges rounded. It does not say this post-processing increases UV protection. Treat surface finishing and outdoor resistance as separate questions; do not present a smoothed surface as proof of improved weathering.

Sources and limits

• Prusament — ASA product statements, printing guidance and qualifications
• Polymaker — PETG technical data sheet V1.0, methods and specimen preparation

We organize manufacturer and community documentation; we have not measured these products ourselves. The manual for your exact model takes precedence over general guidance.