Which filament for outdoor prints?

Outdoor parts face sunlight, heat and moisture. ASA and PETG are options to compare, but the best choice depends on the specific filament, print, exposure and consequences of failure.

The three things that wreck outdoor prints

• UV light. Breaks polymer chains; the part loses tensile strength and surface integrity even before it discolors.
• Heat. Sunlight on a dark print pushes surface temps past 60–70°C in summer. PLA's glass transition is ~60°C — that's why it sags.
• Water + freeze cycles. Hygroscopic filaments absorb water; freezing expansion then opens layer lines into cracks.

The ranking

1. ASA — outdoor king (5/5 outdoor rating)

Acrylonitrile Styrene Acrylate is ABS with a UV-stable backbone. Built specifically for outdoor applications. Actual performance depends on formulation and exposure. Often printed in an enclosed printer and aggressive bed adhesion (warps badly). Examples in our database: Bambu Lab ASA, Polymaker PolyLite ASA.

Printing ASA can release harmful gases, including styrene. Follow the Bambu Lab ASA safety tips and NIOSH guidance on ventilation; an enclosure alone does not establish adequate ventilation.

2. PETG — best easy-mode outdoor option (4/5)

PETG is the practical answer for most hobbyists. Prints on any unenclosed printer, survives moisture in some uses, but performance depends on the exact formulation and conditions. Consider it for non-critical parts and inspect them in use. Stick to lighter colors to reduce heat absorption. Bambu PETG HF, Prusament PETG, Overture PETG are all solid picks.

3. PC — when strength matters more than UV color stability (5/5 mechanically)

Polycarbonate is unbeaten on toughness and heat tolerance. Glass transition above 110°C, so it doesn't sag in summer. Less UV-stable than ASA — yellows over time. Use when the part will see mechanical stress more than direct sun. PolyMax PC is our go-to.

4. ABS — legacy outdoor material, mostly outclassed by ASA

ABS works outdoors but yellows visibly within a single summer of UV exposure and isn't worth the warp-prone print process when ASA exists. Reach for ABS only when you specifically need acetone vapor smoothing or when ASA isn't available.

5. Nylon-CF — niche but powerful (3/5 outdoor)

Carbon-fiber-reinforced nylon is tougher than anything else on this list, but nylon absorbs water like a sponge and isn't UV-stable. Use for engineering parts that live in semi-shaded outdoor environments — drone frames, mounts, structural brackets. Always coat or paint.

The "do not use outdoors" tier

PLA, PLA+, PLA-tough. Heat and sunlight can reduce performance. Check the product and application before use outdoors.

TPU. Variable UV behavior; assume it'll degrade unless explicitly rated.

Quick decision matrix

• Garden ornament, light load: consider PETG; inspect it periodically for damage.
• Mailbox part, weather-exposed: ASA. The classic use case.
• Outdoor mounting bracket under load: PC for strength, or ASA if UV stability also matters.
• Drone landing skids: Nylon-CF if you have a hardened nozzle and enclosure.
• Outdoor electronics enclosure: ASA, with a thin coat of UV-resistant spray for belt-and-suspenders.

Print-time tips for outdoor parts

• Walls + infill: 4 walls and 25%+ infill. Outdoor parts fail at thin shells before they fail at infill.
• Top/bottom layers: 5+ on horizontal surfaces — water finds layer lines.
• Drying: all hygroscopic materials (ABS, ASA, PETG, Nylon, PC) need drying. Bad layer adhesion = water ingress = cracking.
• Color: lighter is cooler. Black ASA in full sun reaches 70°C surface temp; white stays under 50°C.

Bottom line

Default to PETG for general outdoor use, upgrade to ASA when UV stability matters and you have an enclosed printer, and only consider ABS, PC, or Nylon-CF for specific structural or aesthetic needs.