| Spec / Signal | PLA (Typical) | PETG (Typical) | Why It Matters for “Stronger” |
|---|---|---|---|
| Glass Transition (Tg) | 55–60 °C | ~80 °C | Higher Tg usually means stiffness holds up at warmer conditions. |
| Tensile Strength @ Yield | ~60 MPa | ~52 MPa | Yield is the “first big change” point under pulling load; it shapes how parts behave before permanent deformation. |
| Tensile Strength @ Break | ~53 MPa | ~55–59 MPa | Break strength relates to peak pull before failure; in real prints, layers and print orientation can dominate. |
| Tensile Modulus (Stiffness) | ~3.6 GPa | ~1.9 GPa | This is the “does it flex?” number. Higher modulus often feels more rigid in hand. |
| Elongation @ Break | ~6% | ~400% | Big clue for toughness: how much it can stretch before breaking under tensile load. |
| Notched Izod Impact | ~16 J/m | (Commonly reported via film impact tests) | Impact numbers can be test-specific; still, PETG is often discussed as more forgiving under sudden shocks. |
| Heat Deflection Temperature (HDT) | ~55 °C (0.45 MPa) | ~70 °C (0.455 MPa) | HDT is a practical “loaded warmth” indicator. It connects to strength under heat. |
| Density | ~1.24 g/cm³ | ~1.27 g/cm³ | Close in density; strength differences usually come from polymer behavior and print structure. |
| Common Nozzle Temp Window (FDM) | ~180–210 °C (often), sometimes broader | ~215–235 °C (often) | Hotter windows can support layer fusion and reduce voids, which matters for printed-part strength. |
Table values reflect typical manufacturer / literature-reported material data rather than a promise for every spool or every printer. PLA values align with a NatureWorks Ingeo 4043D 3D-monofilament data sheet[a]. PETG values align with an Eastman Eastar 6763 technical information document[b].
When someone asks “PLA vs PETG: which one is stronger?” the honest answer is: it depends on what kind of strength you mean. PLA often leads in stiffness and can show strong tensile behavior in many FDM setups, while PETG is famous for toughness and keeping its mechanical feel better as temperatures rise. Same word, different physics.
Table of Contents
🧪 Keep this in mind: most published “tensile strength” numbers are measured on standardized specimens. FDM parts add layer interfaces, voids, and directionality, so the same filament can behave like two different materials depending on how the part is oriented.
Strength Snapshot
Where PLA Commonly Leads
- Stiffness (higher tensile modulus) often feels solid in bending and light structural loads.
- Yield behavior can look strong in tensile tests when layers are well-fused.
- Crisp detail can preserve geometry, which indirectly supports strength in thin ribs and sharp features.
Where PETG Commonly Leads
- Ductility (very high elongation at break) supports energy absorption instead of sudden fracture.
- Thermal headroom (higher Tg) helps parts keep their mechanical feel in warmer environments.
- Layer bonding is often described as strong and “sticky,” which can help reduce layer-separation failures.
🔩 If “stronger” means resisting bending without flexing much, PLA frequently looks stronger. If “stronger” means surviving drops, impacts, and warm conditions without losing its mechanical character, PETG often feels stronger. Same question, different load story.
What “Stronger” Means in Plastics
- Tensile Strength
- How much pulling stress a material withstands. Look at yield and break as separate moments, not one magic number.
- Modulus (Stiffness)
- How much it deflects under load. PLA’s typical modulus is notably higher than PETG’s in common datasheets[a].
- Toughness
- Energy absorbed before breaking. High elongation is one clue; PETG’s typical elongation at break is dramatically higher in common data[b].
- Impact Behavior
- Response to sudden forces. Test methods vary a lot, so comparisons should stay tied to the same standard.
- Thermal Strength
- How properties hold when warm. Tg and HDT matter because a part can feel “strong” at room temperature and very different near softening.
- Creep
- Slow deformation under constant load over time. For functional parts, time is a real load case.
Why Test Standards Matter
- Specimen geometry changes results (film strips vs dog-bone bars).
- Speed of testing can shift yield and break behavior.
- Temperature and humidity change polymer response.
- FDM directionality means X/Y can differ from Z in a very real way.
ASTM D638 is a widely used tensile standard for plastics test specimens and is a common reference point for comparing tensile property reporting[c].
Material-Level Numbers: What the Datasheets Suggest
PLA as a Material (Typical)
- Higher stiffness is the headline: tensile modulus around 3.6 GPa is a classic “rigid” signal[a].
- Tensile yield around 60 MPa is commonly reported for typical data sets[a].
- Tg around 55–60 °C hints that mechanical feel can change noticeably as parts warm up[a].
- HDT around 55 °C (at 0.45 MPa) is another practical “warm load” indicator[a].
Read that as PLA is naturally stiff. That stiffness can be a big part of why it feels “strong” in many hand-tests and light structural situations.
PETG as a Material (Typical)
- Tg around 80 °C suggests a wider window where parts stay mechanically familiar in warmer use[b].
- Elongation at break can be extremely high (often reported around 400% in typical film-property tables), a strong hint of ductile behavior[b].
- Tensile yield around 52 MPa, with tensile at break often in the mid-to-high 50 MPa range in common data sets[b].
- Modulus around 1.9 GPa points to a more flexible response under the same load compared to PLA[b].
The easy read: PETG is often described as tough and accommodating. It can flex and absorb energy in a way that changes what “strong” feels like.
🧩 One quiet detail that matters: many published numbers are from controlled specimen tests, not a printed bracket with layer lines. For filament comparisons, the print structure can matter as much as the polymer chemistry.
Printed-Part Reality: Why FDM Changes the Answer
Layer Interfaces Are a Material of Their Own
In FDM, the part isn’t a single continuous solid. It’s roads of polymer welded together. That makes strength a story about fusion quality, not just the raw resin. A peer-reviewed FDM study discussing PLA and PETG highlights that printing parameters like temperature and speed shape mechanical performance, and it also notes different typical nozzle temperature ranges reported for each material[d].
- Orientation controls whether load travels along roads or across layer boundaries.
- Porosity acts like tiny cracks; fewer voids usually supports higher effective strength.
- Cooling behavior influences residual stresses and bonding.
Temperature Windows (Information, Not a Rulebook)
Many sources describe PLA printing windows around 180–210 °C and PETG around 215–235 °C in common FDM contexts[d]. Some manufacturer guidance for specific grades can be broader (especially for PLA), which is normal because formulations differ.
🔥 Hotter isn’t automatically “stronger,” but under-melting can leave weak bonds. This is why process context belongs in any honest strength comparison.
A practical way to read FDM strength: material properties set the ceiling, while layer quality and geometry decide how close you get.
PLA Strength Profile
What Makes PLA Feel Strong
- High stiffness (modulus) supports parts that should not flex much under load[a].
- Defined yield behavior can translate to predictable performance in many tensile-like load cases when print bonding is solid.
- Thermal transition around 55–60 °C is a real boundary; below it, PLA often feels very rigid[a].
Strength-Related Notes Engineers Watch
- Stiffness-driven designs (ribs, beams, frames) often match PLA’s natural behavior.
- Thin features can benefit from PLA’s crisp extrusion and stable geometry.
- Heat + load is where Tg and HDT become relevant numbers, not trivia[a].
PETG Strength Profile
What Makes PETG Feel Strong
- Ductility is the star: very high elongation at break is a classic sign of toughness and energy absorption in tensile loading[b].
- Higher Tg (~80 °C) supports a stable mechanical feel in warmer environments, which can matter a lot for functional use[b].
- Useful tensile levels (yield in the ~50 MPa range) keep PETG firmly in the “functional filament” class[b].
Strength-Related Notes Engineers Watch
- Impact-like events often reward a material that can deform and recover rather than crack suddenly.
- Living-hinge-ish flexing and snap-fit behavior usually asks for toughness more than raw stiffness.
- Moisture control matters for many polyesters during processing; PETG-related technical documents often discuss hydrolysis sensitivity in melt, which is why dryness is part of serious mechanical consistency[b].
Visual Meters
🧱 Stiffness (Modulus Feel)
Higher = less flex
🛡️ Toughness (Energy Absorption Feel)
Higher = more forgiving
🌡️ Warm-Environment Mechanical Headroom
Tg/HDT influenced
🧬 Layer-Fusion Sensitivity (FDM Practicality)
Process-dependent
🧠 A simple mental model: PLA often wins the “rigid strength” conversation, PETG often wins the “tough strength” conversation. If you always mean only one definition, write it down first. It saves a lot of confusion.
FAQ
Is PLA stronger than PETG?
It depends on the definition. For stiffness (modulus) and a rigid feel under load, PLA often comes out ahead in typical material data. For toughness (ability to deform and absorb energy), PETG often leads because ductility can be dramatically higher in typical data sets[b].
Why do printed parts behave differently than datasheets?
Datasheets are usually based on standardized specimens tested under controlled conditions. FDM adds layer interfaces, internal structure (infill), and directionality, so the printed object’s “effective material” is a blend of polymer behavior and weld quality. Research on PLA and PETG in FDM highlights how print parameters shift mechanical outcomes[d].
Which one is stronger for heat-exposed functional parts?
Heat changes the game because polymers approach softening behavior as temperature rises. PETG’s typical Tg around 80 °C and common HDT reporting suggest more mechanical headroom in warm environments than PLA’s typical Tg range[b].
What tensile test standard should I trust when comparing numbers?
The important part is consistency: compare values measured with the same standard and specimen type. ASTM D638 is a widely referenced tensile standard for plastics and is commonly used as a baseline for tensile reporting discussions[c].
Sources
-
[a]
NatureWorks LLC — “Ingeo Biopolymer 4043D Technical Data Sheet (3D-monofilament)”.
Official PDF -
[b]
Eastman — “MBS-80Q Eastar Copolyester 6763 Technical Information”.
Official PDF -
[c]
ASTM International — “ASTM D638: Standard Test Method for Tensile Properties of Plastics”.
Standard Page -
[d]
Polymers (MDPI) — “Effect of Printing Parameters on the Thermal and Mechanical Properties of 3D-Printed PLA and PETG, Using Fused Deposition Modeling” (2021).
Publisher Page