| Attribute | PLA | PETG | Notes (What The Number Represents) |
|---|---|---|---|
| Polymer Family | Polylactic Acid (aliphatic polyester) | PETG (glycol-modified copolyester) | Polyester chemistry in both, different chain behavior and softening profile. |
| Glass Transition (Tg) | 59.1 °C | 77.4 °C | Tg is where the material starts to feel rubbery; a key heat threshold. |
| Heat Deflection Temp (0.455 MPa) | 58.8 °C | 76.2 °C | HDT compares shape stability under load when warmed. |
| Vicat Softening Temperature | 64.5 °C | 82.9 °C | Vicat is another view of softening at elevated temperature. |
| Melting Temperature (DSC) | 151.8 °C | — (amorphous) | PETG often shows no sharp melting peak; it softens through a broad window. |
| Specific Gravity | 1.24 g/cm³ | 1.27 g/cm³ | Affects spool length per kg and part mass for the same volume. |
| Tensile (Young’s) Modulus (XY) | 3250 ± 119 MPa | 1939 ± 28 MPa | Stiffness signal: higher modulus usually feels more rigid in hand. |
| Tensile Stress At Yield (XY) | 52.5 ± 0.9 MPa | 46.2 ± 0.8 MPa | Yield shows when permanent deformation begins under tension. |
| Elongation At Break (XY) | 7.8 ± 1.2% | 7.6 ± 0.2% | Similar headline values here; printed orientation shifts the feel a lot. |
| Charpy Impact Strength, Notched (23 °C) | 3.9 ± 0.4 kJ/m² | 7.9 ± 0.6 kJ/m² | A direct look at impact energy absorption in a standardized test. |
| Hardness (Shore D) | 84 | 76 | Higher Shore D often correlates with a more crisp surface feel. |
| Common Nozzle Temperature (Example Profiles) | 215 °C first layer, 210 °C other layers | 230 °C first layer, 240 °C other layers | Profile examples from Prusa material pages ✅Source and ✅Source |
| Common Bed Temperature (Example Profiles) | 60 °C | 85–90 °C | Bed heat supports first-layer consistency; exact values depend on printer and surface. |
About These Numbers PLA and PETG figures above come from standardized tests on 3D-printed specimens, so they feel closer to real parts than raw-pellet data. The exact outcome still shifts with infill, layer height, and orientation.
- Material Identity and Polymer Structure
- PLA As A Material
- PETG As A Material
- Thermal Behavior and Heat-Related Numbers
- What Tg Explains In Real Prints
- HDT and Vicat In One View
- Mechanical Feel Across Stiffness, Yield, and Impact
- Stiffness Signals From The Datasheet
- Impact and Energy Absorption
- Print Behavior Across Temperature, Flow, and Bed Interaction
- PLA Flow Personality
- PETG Flow Personality
- Surface Character In PLA and PETG
- Detail and Edge Definition
- Post-Processing Expectations
- Moisture, Consistency, and Spool Reality
- Common Use Patterns For PLA and PETG
- PLA Often Seen In
- PETG Often Seen In
- Common Comparison Questions People Ask
- Is PETG “Stronger” Than PLA?
- Why Does Tg Matter If A Part Never Reaches Tg?
- Why Does Orientation Keep Appearing In Datasheets?
PLA and PETG are the two headline 3D printing filaments in everyday FDM work. They overlap more than people expect, yet their thermal behavior and mechanical feel give them distinct personalities in prints.
Material Identity and Polymer Structure
PLA As A Material
PLA filament is a polylactic acid polyester. In prints, it often reads as stiff and clean-edged, which is why it shows up in visual prototypes and detailed geometry.
- Higher modulus signal in typical tests (rigid feel)
- Distinct melting peak in DSC (clear melt behavior)
- Common default choice for wide printer compatibility
PETG As A Material
PETG filament is a glycol-modified PET copolyester. It often reads as tough and ductile, with a higher softening window than PLA in typical printed-part data.
- Higher HDT in typical printed tests (shape holds longer when warmed)
- Amorphous melt profile in DSC (no sharp melting point)
- Strong layer fusion feel in many functional geometries
- Key Word: Glass Transition (Tg)
- Tg is the temperature zone where a printed part starts moving from a rigid feel toward a more rubbery response. It helps explain heat sensitivity in real use and why Vicat and HDT show up in datasheets.
- Key Word: Amorphous
- When a polymer is amorphous, it typically softens across a broader range rather than showing a sharp melting peak. That’s why PETG often lists no melting temperature in DSC tables while still printing smoothly.
Thermal Behavior and Heat-Related Numbers
PLA centers around a ~59 °C Tg in printed-part data, while PETG centers around a ~77 °C Tg. That single gap often shows up as a practical difference in how parts behave near warm environments, especially when load is involved.
What Tg Explains In Real Prints
- Shape Feel shifts: stiffness starts relaxing as Tg is approached.
- Press-Fit Response changes: snap features can feel different near warm zones.
- Surface Marking can increase if a part is stressed while softened.
HDT and Vicat In One View
HDT adds a load condition, while Vicat focuses on softening under a probing force. Seeing PLA lower than PETG in both lines up with PETG’s higher softening window in many printed datasheets.
Relative Signals (Example Comparison)
Mechanical Feel Across Stiffness, Yield, and Impact
PLA shows a higher Young’s modulus in typical printed-part tables, which often reads as a more rigid part for the same geometry. PETG tends to show more of a tough, yielding behavior, which can be valuable when parts see repeated flexing in service.
Stiffness Signals From The Datasheet
- PLA modulus (XY) is listed around 3250 MPa, supporting a firm feel.
- PETG modulus (XY) is listed around 1939 MPa, supporting a more forgiving response.
- Geometry still matters: ribs and wall thickness can dominate the experience.
Impact and Energy Absorption
In notched Charpy values, PETG is shown with a higher typical number than PLA in the referenced printed-part data. That difference can show up in parts that experience drops, knocks, or sudden loading.
- PLA notched Charpy: 3.9 kJ/m² (typical)
- PETG notched Charpy: 7.9 kJ/m² (typical)
Print Behavior Across Temperature, Flow, and Bed Interaction
Nozzle temperature and bed temperature are not just “settings”; they define how the melt supports bridges, how edges stay crisp, and how layers fuse. Example profiles show PLA running at lower nozzle temperatures than PETG, matching their different softening and flow behavior.
Temperature References shown in the table come from Prusa’s material pages for PLA and PETG. They are examples, not a universal rule for every brand and printer.
PLA Flow Personality
- Crisp corners are common, supporting sharp detail.
- Cooling response often keeps thin features visually clean.
- Lower heat window aligns with lower Tg and HDT numbers in typical tables.
PETG Flow Personality
- Layer fusion often feels very strong on functional shapes.
- Higher nozzle heat supports consistent flow in many profiles.
- Bed interaction can be very firm, which is why surface choice matters.
Surface Character In PLA and PETG
PLA frequently presents a clean surface that supports small text, sharp edges, and a “finished” look straight off the printer. PETG often presents a smoother, glossier look, and translucency can be especially striking with the right color and wall thickness.
Detail and Edge Definition
- PLA often shows crisp edges on fine geometry.
- PETG often shows smooth walls and a polished sheen.
- Both can look excellent; layer height and line width steer the final appearance.
Post-Processing Expectations
Both PLA and PETG can be sanded and finished, yet they can respond differently because of their softening range and surface feel. For many users, the biggest visible difference is how the surface transitions between matte and gloss across lighting and color.
Moisture, Consistency, and Spool Reality
PLA and PETG are both hygroscopic to some degree, meaning moisture can change how the filament behaves in the hotend. When moisture is present, the most common signal is a change in extrusion consistency and surface texture rather than a change in base chemistry.
- Moisture shows up as process variation more than “material quality.”
- Diameter tolerance and roundness affect flow stability for both materials.
- Pigments can shift appearance and feel while staying within the same material family.
Common Use Patterns For PLA and PETG
PLA often appears in parts where visual clarity, crisp detail, and predictable stiffness matter. PETG often appears in parts where a broader heat window and higher impact energy signal are valuable.
PLA Often Seen In
- Display models and visual prototypes
- Geometric parts with sharp edges and small text
- Jigs where stiffness helps maintain alignment
PETG Often Seen In
- Functional housings and everyday components
- Parts near warmth where higher HDT/Vicat help
- Snap features that benefit from a yielding response
Common Comparison Questions People Ask
Is PETG “Stronger” Than PLA?
“Strength” depends on the definition. In the referenced printed-part data, PLA shows a higher modulus (stiffness signal), while PETG shows a higher impact number. They shine in different mechanical dimensions.
Why Does Tg Matter If A Part Never Reaches Tg?
Tg still influences behavior below the exact number because it maps the transition zone. A part can show different creep response and surface feel as it approaches that window, which is why HDT and Vicat are often read alongside it.
Why Does Orientation Keep Appearing In Datasheets?
FFF parts are layered structures. A change in print orientation changes how loads travel through roads and layers. That’s why the same material can show different values in XY, YZ, and Z directions in standardized testing.
