PLA and PETG sit next to each other on the shelf, cost roughly the same, and both print on a stock Ender 3. That’s where the similarities end. PLA snaps under load, deforms in a hot car, and melts in direct sun. PETG strings like crazy, sticks too well to PEI, and absorbs moisture within hours. Pick the wrong one for your application and the part fails — either immediately or when it matters most.
Mechanical Properties — The Numbers That Matter
PLA (Polylactic Acid)
- Tensile strength: 50-60 MPa — high for a 3D printed material
- Flexural modulus: 3,500-4,000 MPa — extremely stiff, almost no flex before failure
- Elongation at break: 3-6% — brittle failure, no warning before snapping
- Impact resistance (Izod): 2-5 kJ/m² — poor, shatters under impact
- Glass transition temperature (Tg): 55-60°C — deforms in direct sunlight or a hot car
- Density: 1.24 g/cm³ — standard weight
PLA is stiff and strong but brittle. A PLA bracket holds static load well but shatters on the first impact. At 55°C, PLA begins to soften — a PLA print left on a car dashboard on a summer day will permanently warp.
PETG (Polyethylene Terephthalate Glycol)
- Tensile strength: 45-50 MPa — slightly lower than PLA
- Flexural modulus: 2,000-2,500 MPa — flexes before breaking, less stiff
- Elongation at break: 10-20% — ductile failure, bends and stretches before snapping
- Impact resistance (Izod): 8-12 kJ/m² — 3-4x better than PLA
- Glass transition temperature (Tg): 80-85°C — survives hot cars, direct sun, near electronics
- Density: 1.27 g/cm³ — marginally heavier than PLA
PETG trades some stiffness for impact resistance and heat tolerance. A PETG bracket bends under load but doesn’t crack. At 80°C, PETG holds its shape — it can sit in a hot car or next to a printer heated bed without deforming.
The Practical Outcome
PLA is for display pieces, prototypes, and indoor-only applications where there’s no load, no impact, and no heat. PETG is for functional parts — mounts, brackets, drone accessories, and anything that lives outdoors or near heat sources. For FPV drone parts specifically: never use PLA. A PLA GoPro mount will snap on the first hard landing. A PETG mount survives crashes that total the frame.
Printability and Settings
| Property | PLA | PETG | Winner |
|---|---|---|---|
| Nozzle temperature | 190-220°C | 230-250°C | PLA (lower temps = less wear on PTFE) |
| Bed temperature | 50-60°C | 70-85°C | PLA (lower temps = less energy, less warping) |
| Bed adhesion | Excellent on PEI, glass, BuildTak | Too good on PEI — use glue stick as release agent | PLA (easier to remove) |
| Stringing | Minimal | Heavy without tuned retraction | PLA (less post-processing) |
| Warping | Very low | Low (higher than PLA but manageable) | PLA (barely warps) |
| Moisture sensitivity | Low (absorbs <1% in 24h) | High (absorbs 3-5% in 24h, must dry) | PLA (print from open spool) |
| Odor | Mild, slightly sweet | Very low, nearly odorless | PETG (less noticeable) |
| First layer forgiveness | Very forgiving | Demands a perfect Z-offset | PLA (easier for beginners) |
| Bridging | Excellent | Poor — droops and sags | PLA (cleaner bridges) |
| Overhangs | Good | Adequate with cooling | PLA (cleaner overhangs) |
| Part cooling fan | 100% | 30-50% (too much causes layer adhesion loss) | PLA (simpler cooling) |
| Nozzle wear | Standard brass fine | Hardened steel or plated copper recommended | PLA (standard nozzle OK) |
Real-World Use Cases
When to Use PLA
- Decorative models, figurines, vases
- Prototypes and fit-check parts
- Indoor organizers, desk accessories
- Items that won’t see heat, impact, or outdoor exposure
- Lithophanes (PLA’s stiffness and opacity work well)
- Teaching and classroom prints (easy, forgiving)
When to Use PETG
- Drone parts: GoPro mounts, antenna holders, GPS mounts, skids
- Automotive interior parts (survives 80°C car interior)
- Outdoor enclosures and brackets
- Mechanical parts with snap fits (PETG flexes, PLA snaps)
- Anything near a heated bed, PSU, or electronics enclosure
- Tool holders and workshop fixtures that see impact
The “Just Use PETG” Rule
If you’re not sure, use PETG. It costs $2-3 more per kilogram and takes 10 extra minutes to dial in settings, but a failed PLA print that breaks costs more time and filament than the upfront tuning. For functional parts, PETG is the default — PLA is the exception.
Common PLA vs PETG Mistakes
Mistake 1: Printing PETG With PLA Settings
Loading PETG and hitting print on your PLA profile produces a mess. PETG needs 230-250°C nozzle, 70-85°C bed, lower fan speed, and different retraction. Fix: Create a separate PETG profile in your slicer. Never swap filament without swapping profiles.
Mistake 2: Using PLA for Outdoor or In-Car Parts
PLA’s 55°C glass transition means a sunny day destroys the part. Dashboard temps hit 70°C in summer. A PLA phone mount in your car lasts exactly one afternoon. Fix: If the part will see sunlight, a hot car, or outdoor summer heat, use PETG or ABS/ASA. PLA is indoor-only.
Mistake 3: Printing PETG on Bare PEI Without a Release Agent
PETG bonds to PEI so well it can tear the PEI surface when you remove the print. A 50-hour print that rips off chunks of your build plate is a bad day. Fix: Apply a thin layer of glue stick (or dedicated release agent) to PEI before printing PETG. The glue acts as a sacrificial interface.
Mistake 4: Overcooling PETG
PLA cooling at 100% fan works great. PETG at 100% fan produces beautiful-looking prints that delaminate between layers because the plastic cooled before bonding. Fix: Run part cooling at 30-50% for PETG. Layer adhesion comes from heat — too much cooling kills it.
⚠️ Safety Notice: Both PLA and PETG are generally considered safe for home 3D printing, but all FDM printing emits micro-particles and volatile organic compounds. PLA emits lactide (mild, sweet smell), while PETG emits minimal VOCs. Always print in a well-ventilated area. For enclosure-printed materials like ABS/ASA, dedicated ventilation is mandatory. Verify your printing setup complies with 2026 electrical safety standards — heated beds and hotends operate at temperatures that can ignite flammable materials if left unattended.
As we detailed in our 3D Printer Bed Adhesion guide, the surface you print on changes everything — PEI is the standard for both PLA and PETG, but PETG demands a release agent to prevent permanent bonding. If you’re printing in an enclosure for temperature-sensitive materials, our 3D Printer Enclosure DIY Build guide covers ventilation and temperature control for consistent results regardless of filament choice.
Stringing — PETG’s primary headache — is solvable with proper retraction tuning. Our 3D Printer Stringing and Oozing guide walks through retraction distance, speed, and travel optimization for PETG and other string-prone filaments.
For FPV drone parts, PETG is the baseline material. TPU is better for impact absorption, but PETG handles the structural roles — antenna mounts, GPS holders, and skid plates all benefit from PETG’s heat resistance and impact tolerance. The Polymaker PolyLite PETG prints clean at 235°C/75°C on any standard printer and has become the go-to for drone builders who need functional parts that survive real-world abuse.