Heat, moisture and sunlight: which 3D printing material will last
A part that works on the desk can fail in a hot car, a damp cellar or direct sun. This guide explains how the four materials we mainly print with, PLA, PETG, ABS and TPU, behave in those conditions, using typical values rather than guarantees.
Heat
PLA softens at around 55-60 °C, so it can deform in a car parked in summer. PETG tolerates about 70-80 °C and ABS about 95-105 °C. TPU stays flexible, but it also softens as the temperature rises, so check its datasheet. In every case the safe service temperature is below these figures, because a part under load deforms before it reaches the softening point.
Remember that the temperature of the part is not the temperature of the air. A dark part in direct sun, or a part next to a motor, heater or lamp, can be much warmer than its surroundings.
Moisture and chemicals
PETG is a good choice for damp places and handles many cleaning agents. ABS tolerates water well but is attacked by acetone and some solvents. PLA slowly degrades in hot, humid conditions. TPU is generally tolerant of oils and water.
If a part will meet a specific chemical such as a fuel, a strong cleaner or a solvent, name it in your request. Chemical resistance depends on the exact substance, the concentration and the time of contact, so a general table is only a first filter.
Sunlight and outdoor use
Ultraviolet light yellows and embrittles ABS and PLA over time, and PETG holds up better. For long outdoor service, paint or coat the part and tell us about the exposure: sun, rain, temperature swings and cleaning agents all matter. A painted surface also hides the layer pattern, which many outdoor parts benefit from.
Matching the material to the conditions
| Environment | First choice | Notes |
|---|---|---|
| Indoor, room temperature | PLA | Best surface, easiest to print |
| Hot place, near its limits | ABS | Keep well below its softening point |
| Damp or wet place | PETG | Good moisture and chemical resistance |
| Outdoors, long service | PETG, painted or coated | Tell us the exposure |
| Flexible, in contact with oil or water | TPU | Generally tolerant of oils and water |
Use the table as a first filter, then check the datasheet of the actual filament. For the general comparison of strength and flexibility, see our material guide. If a part has to do two things at once, such as be flexible and survive heat, tell us and we will look for a compromise.
Cars and other hot places
The interior of a car parked in the sun can become far hotter than the outside air, and a dark dashboard hotter still. This is the most common way for a PLA part to fail. If a part will ever sit in such a place, pick ABS, and use PETG only where measured temperatures stay below about 60 °C. Keep a safety margin below the softening temperature of the material.
Service life and ageing
All plastics change slowly over time. A part that works on delivery can become more brittle after months of sun, heat or chemical contact. If the part has to last for years, say so, and plan an inspection or a replacement interval instead of assuming that it will last forever.
A simple way to test before you commit
When the conditions are uncertain, print one sample and test it where it will really work. Leave it in the hot place or in the sun for a few days, put it in water or in contact with the cleaning agent, and load it as it will be loaded in use. Compare it with an untouched sample. A test like this costs little and answers questions that no table can.
Think about the whole year
A part used in winter and summer sees both cold and heat. Many plastics become more brittle in the cold, and softer in the heat. If the part is outdoors, check both ends of the temperature range, not only the warm one.
A note on TPU
TPU is chosen for flexibility, not for heat. It stays elastic over a wide range of temperatures and copes well with oils and water, but a soft grade under load in a warm place can stretch permanently. If a flexible part will be hot, loaded or stretched for long periods, say so, and we will advise on a grade and on the design.
Describe the conditions to us
- The highest temperature the part will see, and for how long.
- Contact with water, oil, fuel or cleaning agents.
- Indoor or outdoor use, and how much direct sun.
- The load on the part and how often it is applied.
With these four answers we can recommend a material. Send us your file with a short description of where the part will work.
Cover photo: Jakub Żerdzicki(opens in a new tab) on Unsplash(opens in a new tab).