UV-resistant and heat-resistant filament compared
are explained briefly when you hover over or tap them.
In short: according to manufacturer datasheets, PLA softens at around 55 °C and is suitable neither for a car in summer nor for permanent sun. PETG withstands a little more, around 68 °C, and is usable for many outdoor parts. For parts that get hot and sit in the sun, ASA with 93 to 96 °C and high UV resistance is the obvious choice. PC tolerates even more heat, but ages in sunlight without protection.
The details, manufacturer values and pitfalls are below.
How hot does it actually get?
In a heat test, the ADAC (the German automobile club) measured parked cars in the sun. The interior of the reference vehicle without sun protection reached 53 °C. According to the ADAC, over 60 °C is also quickly possible in a parked car, and the steering wheel and dashboard got hotter than 70 °C.
For 3D prints this means that a phone holder on the dashboard or a clip on the windscreen has to withstand much more than a part in the boot. Outdoors, UV light adds to the heat, bleaching plastics and making them brittle.
What the numbers in the datasheet mean
Manufacturers specify heat resistance in different ways. The values are therefore not directly comparable.
| Value | What is measured |
|---|---|
| HDT (heat deflection temperature, ISO 75 or ASTM D648) | Temperature at which a test bar deforms under a defined bending load. Given together with the load, usually 0.45 MPa or 1.8 MPa. At 1.8 MPa the value is the same or lower. |
| Vicat (ISO 306 or ASTM D1525) | Temperature at which a loaded needle penetrates the sample. Usually higher than the HDT. |
| Glass transition temperature (Tg) | Temperature above which a plastic changes from hard and glass-like to soft and rubbery. According to Polymaker, for amorphous plastics it is usually regarded as the highest service temperature. |
Keep two things in mind when reading:
- The test specimens are solid. Extrudr writes in its datasheets that temperature resistance was tested at a wall thickness of at least 4 mm. Polymaker points out that thin walls and low infill give way under heat much faster than a thick, dense part made from the same filament.
- Load matters. A part that just lies around tolerates more than a bracket with a phone hanging from it or one that is clamped under tension.
So plan with a margin to the datasheet value. If the expected temperature is close to the HDT, the material is too marginal.
The materials compared
The values are examples from current manufacturer datasheets. Other brands and variants (matte, silk, CF, high speed) can differ considerably. What counts is always the datasheet of your spool.
| Material | Heat resistance according to manufacturer | UV resistance according to manufacturer |
|---|---|---|
| PLA | HDT 55 °C (Prusament PLA, 0.45 MPa), HDT 57 °C (Bambu Lab PLA Basic, 0.45 MPa) | low (Prusa) |
| PETG | HDT 68 °C (Prusament PETG, 0.45 MPa), Vicat 78 °C (Extrudr PETG) | suitable for indoor use and most outdoor applications (Prusa) |
| ABS | HDT 85 °C, Vicat 92 °C (Extrudr DuraPro ABS) | lacking (Prusa: “lacks UV resistance”) |
| ASA | HDT 93 °C (Prusament ASA, 0.45 MPa), HDT 96 °C (Extrudr DuraPro ASA) | high (Prusa, Polymaker, Extrudr) |
| PC | 113 °C (Prusament PC Blend), according to Polymaker HDT above 115 °C | degrades under prolonged sun unless coated (Polymaker) |
| Nylon (PA) | PA11: HDT 58.7 °C (0.45 MPa), up to 122.5 °C after annealing (Prusament PA11); PA12: Vicat 142 °C (Extrudr DuraPro PA12) | PA11: high (Prusament) |
| TPU | HDT 78.6 °C (1.8 MPa), Vicat 101.6 °C (Prusament TPU 95A); Vicat 110 °C (Extrudr Flex Medium) | depends on the grade, see below |
PLA: only for indoors and shade
For Prusament PLA, Prusa gives a temperature resistance of 55 °C and writes that parts lose mechanical strength from above 60 °C. On top of that comes the low UV resistance. Prusa therefore considers PLA not ideal for outdoor use. In a car in summer, even the interior air temperature measured in the ADAC test, 53 °C, is close to this value, and on the dashboard it is well above it.
There are exceptions: Polymaker offers an HT-PLA that is said by the manufacturer to stay dimensionally stable up to 150 °C, and for a matte PLA grade it states weathering tests at ASA level. These are properties of these special products, not of PLA in general. For special PLAs, only the datasheet of the respective grade counts.
PETG: the outdoor compromise
According to the Prusament datasheet, PETG withstands around 68 °C. Prusa considers it suitable for indoor use and most outdoor applications, and Polymaker describes it as resistant to UV light. For garden parts, brackets on the balcony or parts in the boot, PETG is therefore often sufficient. Directly behind the windscreen or on the dashboard, where the ADAC measured over 70 °C, it gets tight.
ABS: heat-resistant, but not sun-resistant
With an HDT of 85 °C (Extrudr), ABS copes well with heat. However, Prusa explicitly lists the lack of UV resistance as a disadvantage and names ASA as the successor with exactly this strength. ABS is therefore suitable for warm parts in the shade, for example on appliances, and less so for permanent sun.
ASA: the choice for sun and heat
ASA combines heat resistance similar to ABS (93 to 96 °C) with high UV resistance. For its ASA, Polymaker states a two-year outdoor test: afterwards the colour change was a ΔE below 2.5 and the parts remained intact. For parts on the outside of a car, on the house or in the garden, ASA is therefore the obvious material. It is, however, harder to print than PETG, and an enclosed printer helps considerably. More on this under Printing ASA.
PC: for high temperatures, with UV protection
Polycarbonate tolerates more heat than ASA. Prusa names PC Blend for parts exposed to heat such as fan ducts, and Polymaker states an HDT of over 115 °C. According to Polymaker, however, PC degrades under prolonged exposure to sun if it is not coated. For hot parts in the sun this means: paint the PC, or use ASA if its temperature range is enough.
Nylon: widely scattered values
For nylon there is no single value. Prusament PA11 reaches an HDT of only 58.7 °C unannealed, up to 122.5 °C after annealing according to Prusa, and has high UV resistance according to the manufacturer. Extrudr gives a Vicat value of 142 °C for its PA12. According to Polymaker, carbon or glass fibres raise the heat deflection temperature further. Note also: according to Polymaker, nylon slowly absorbs moisture from the air again after annealing.
TPU: soft, but surprisingly heat-resistant
TPU is soft even at room temperature, and Extrudr gives a glass transition temperature of −30 °C for Flex Medium. The Vicat values are nevertheless 101.6 °C (Prusament TPU 95A) and 110 °C (Extrudr Flex Medium). On UV resistance the sources contradict each other: Extrudr and Polymaker describe their TPU as UV-resistant, while Henkel’s Loctite guide attributes poor weathering resistance to UV to thermoplastic polyurethane. Here the individual grade decides, so check the datasheet.
Which material for what?
| Use | Suitable materials | Note |
|---|---|---|
| Home, no sunny window | PLA, everything else | no special requirements |
| Windowsill in the sun | PETG, ASA | PLA can warp and bleaches |
| Car, boot or interior in the shade | PETG, ABS, ASA | air temperature up to 53 °C in the ADAC test, over 60 °C also possible |
| Car, dashboard or behind the glass | ASA, PC | surfaces over 70 °C according to the ADAC |
| Garden, balcony, house wall | ASA, PETG | ASA for permanent sun and a long service life |
| Flexible parts outdoors | TPU | check the manufacturer’s UV information |
| Hot parts on a machine, not in the sun | ABS, PC, nylon | allow a margin to the datasheet value |
How to make a part last longer
- Make walls thicker. More walls and more infill help against deformation under heat, see Walls and top layers and Infill.
- Anneal where the manufacturer provides for it. For semi-crystalline materials such as nylon or HT-PLA, annealing raises heat resistance according to Polymaker. For amorphous materials such as PETG, ABS and ASA, it mainly relieves stress. Parts can warp in the process, so follow the manufacturer’s instructions.
- Paint against UV. A clear coat with UV protection can protect the colour, and Polymaker recommends a coating for PC. How to do this is covered under Post-processing 3D prints.
- Choose light colours. The ADAC measured that dark surfaces heat up more: on black paint it was 65 °C, on white 44 °C.
Which material is printed how is covered in the filament overview. For ABS, ASA and PC you usually need an enclosed printer, and you will find a selection under enclosed 3D printers.
Sources
- ADAC: Hitze im Auto, was hilft wirklich?
- Prusament: PLA, PETG, ASA, PC Blend, PA11, TPU 95A
- Prusament datasheets: PETG (PDF), ASA (PDF), PA11 (PDF), TPU 95A (PDF), PLA (ZIP with PDF)
- Bambu Lab: PLA Basic datasheet (PDF)
- Extrudr datasheets: PETG (PDF), DuraPro ABS (PDF), DuraPro ASA (PDF), DuraPro PA12 (PDF), Flex Medium (PDF)
- Prusa Knowledge Base: ABS, ASA, PETG, PLA, Nylon
- Polymaker Wiki: PETG, PC, TPU, PA, ASA, HT-PLA, PLA can be weather-resistant, Wall thickness and heat resistance, Annealing, Temperature and polymers
- Henkel: Loctite Design Guide for Bonding Plastics (PDF), section on polyurethanes