PLA vs ABS: Which Is Actually Stronger? Tensile Strength vs. Toughness Explained
The "Strength" Problem in 3D Printing
Search for "PLA vs ABS strength" and you'll find dozens of comparison tables claiming ABS is the stronger material. Many guides rate PLA as "Low-Medium" strength and ABS as "High" — and then recommend ABS for anything structural.
This is misleading. PLA is measurably stronger than ABS in standardized tensile testing [1]. What ABS actually excels at is toughness — the ability to absorb energy and deform without breaking. These are fundamentally different material properties, and conflating them leads to bad material choices.
The word "strength" in 3D printing discussions almost always conflates three separate properties: tensile strength, impact toughness, and heat resistance. Understanding the difference is the key to choosing the right filament for your application.
Tensile Strength: PLA Wins
Tensile strength measures how much pulling force a material can withstand before it fails. It's tested using the ASTM D638 standard [1] — a dog-bone-shaped specimen is clamped at both ends and pulled apart at a controlled rate until it breaks.
The results aren't even close:
The Numbers
What This Means in Practice
PLA can handle roughly 60% more static pulling force than ABS before breaking. If you're designing a bracket, a clip, or a mounting plate that needs to resist a steady load without deforming, PLA is the stronger choice.
The catch is how they fail. PLA snaps — cleanly and suddenly, with little warning. ABS yields — it stretches, deforms, and gives you visual warning before it ultimately breaks. This difference in failure behavior is where the confusion about "strength" originates.
Impact Toughness: ABS Wins
Toughness measures how much energy a material can absorb before fracturing. While tensile strength answers "how much force can this handle?", toughness answers "how much abuse can this survive?"
ABS is significantly tougher than PLA. It absorbs impacts, flexes under stress, and resists cracking. This is why ABS is used in LEGO bricks [6], automotive trim, and protective housings — applications where parts get dropped, bumped, and stressed repeatedly.
Brittle vs. Ductile Failure
The fundamental difference comes down to how each material behaves under stress:
- PLA is brittle — it resists deformation up to a high threshold, then shatters with little warning
- ABS is ductile — it begins to deform earlier but absorbs far more energy before actually breaking
- PLA cracks propagate quickly — once a crack starts, it runs through the part
- ABS cracks propagate slowly — the material yields and blunts crack tips, resisting further propagation
Drop a PLA part on concrete and it may shatter into pieces. Drop the same part printed in ABS and it will likely bounce or dent. That's toughness in action.
When Toughness Matters More Than Strength
Choose ABS (or another tough material) when your part will experience:
- Impact loads — drops, collisions, or sudden forces
- Repeated stress cycles — parts that flex back and forth over time
- Vibration — motor mounts, drone frames, or anything on a moving platform
- Accidental abuse — phone cases, tool handles, protective covers
If your part might get dropped, hit, or stressed in unpredictable directions, toughness matters more than raw tensile strength.
Heat Resistance: ABS Wins Again
The third property people fold into "strength" is heat resistance, and here ABS has a clear advantage.
| Property | PLA | ABS |
|---|---|---|
| Glass Transition Temp | ~55-60°C [4] | ~100-105°C [5] |
| Practical Heat Limit | ~50°C | ~90°C |
| Softens In Hot Car? | Yes | No |
| Dishwasher Safe? | No | Limited |
Why This Matters
PLA begins to soften around 55-60°C [4] — a temperature easily reached inside a parked car, near a window in direct sunlight, or next to heat-generating electronics. A PLA part that's perfectly strong at room temperature can warp, sag, or lose its shape entirely at moderate heat.
ABS handles temperatures up to about 100°C before softening [5], making it suitable for under-hood automotive parts, electronics enclosures near heat sources, and any application where temperatures might climb above 50°C.
When someone says ABS is "stronger" for a car dashboard mount or an electronics case, they're usually talking about heat resistance — not tensile strength.
The Full Comparison
Here's an honest comparison that separates each property instead of lumping everything under "strength":
| Property | PLA | ABS | Winner |
|---|---|---|---|
| Tensile Strength | ~65 MPa [2] | ~40 MPa [3] | PLA |
| Impact Toughness | Low | High | ABS |
| Heat Resistance (Tg) | ~55-60°C [4] | ~100-105°C [5] | ABS |
| Stiffness (Young's Modulus) | ~3.5 GPa [7] | ~2.0 GPa [7] | PLA |
| Elongation at Break | ~6% | ~20% | ABS |
| Print Difficulty | Easy | Moderate | PLA |
| Warping Risk | Very Low | High | PLA |
| Odor / Fumes | Minimal | Noticeable (ventilate) | PLA |
| UV Resistance | Poor | Moderate | ABS |
| Layer Adhesion | Excellent | Good | PLA |
Why Comparison Charts Get It Wrong
Most "PLA vs ABS" comparison tables rate overall "strength" as a single metric — and almost always give the edge to ABS. This happens for a few reasons:
- Historical context — ABS was the original FDM filament and was compared against early, low-quality PLA formulations that genuinely were weaker
- Industrial reputation — ABS is used in injection-molded products (LEGO, car parts, appliances) [6], which creates a perception of it being the "serious" engineering material
- Conflation of properties — writers combine tensile strength, impact resistance, and heat resistance into one "strength" rating, and since ABS wins two out of three, it gets the higher score
- Copy-paste problem — inaccurate ratings get repeated across blogs and buying guides without anyone checking the ASTM D638 data [1]
The ASTM D638 tensile testing standard [1] is unambiguous: PLA's ultimate tensile strength is approximately 65 MPa [2], while ABS's is approximately 40 MPa [3]. These are well-established figures published in material data sheets from manufacturers worldwide.
Choosing the Right Material: A Practical Guide
Instead of asking "which is stronger?", ask these questions about your specific part:
Choose PLA When
- The part needs to resist steady, static loads (shelf brackets, mounts, clips)
- Maximum stiffness matters (the part shouldn't flex at all)
- The part will stay indoors at room temperature
- Surface finish and dimensional accuracy matter
- You want the easiest possible print with the least troubleshooting
- You're prototyping and want reliable results quickly
Choose ABS When
- The part may be dropped, hit, or subjected to sudden impacts
- Heat exposure above 50°C is possible (cars, electronics enclosures, outdoor use)
- The part needs to flex repeatedly without cracking
- Long-term UV exposure is a concern
- You need a material that can be sanded, acetone-smoothed, or chemically welded
Consider Alternatives
- PETG — If you want better toughness than PLA with easier printing than ABS, PETG is often the best compromise. It has moderate tensile strength (~50 MPa) [8], good impact resistance, and a glass transition temperature around 80°C.
- PLA+ / Tough PLA — Modified PLA formulations from brands like Polymaker, Overture, and SUNLU that improve impact resistance while retaining most of PLA's printability and tensile strength.
- ASA — ABS's UV-resistant cousin, ideal for outdoor applications where both toughness and weather resistance matter.
The Bottom Line
PLA is stronger. ABS is tougher. These are not the same thing.
PLA handles more tensile force before breaking (~65 MPa vs ~40 MPa per ASTM D638 [1]), making it the better choice for static load-bearing applications at room temperature. ABS absorbs more impact energy, resists cracking, handles heat, and flexes instead of snapping — making it better for parts that get dropped, bumped, or exposed to temperature swings.
Next time you see a chart rating ABS as "High" strength and PLA as "Low-Medium," ask yourself: strength in what sense? The answer changes which filament you should reach for.
Sources
- [1]ASTM D638, "Standard Test Method for Tensile Properties of Plastics" — the standard test for measuring tensile strength of thermoplastics. https://www.astm.org/d0638-22.html
- [2]NatureWorks, "Ingeo Biopolymer 4043D Technical Data Sheet" — PLA ultimate tensile strength ~65 MPa. https://www.natureworksllc.com/products/ingeo-biopolymer-4043d
- [3]SABIC, "Cycolac MG94 ABS Technical Data Sheet" — ABS ultimate tensile strength ~40 MPa. https://www.sabic.com/en/products/polymers/acrylonitrile-butadiene-styrene-abs
- [4]NatureWorks, "Ingeo Biopolymer 4043D Technical Data Sheet" — PLA glass transition temperature (Tg) 55–60°C. https://www.natureworksllc.com/products/ingeo-biopolymer-4043d
- [5]SABIC, "Cycolac MG94 ABS Technical Data Sheet" — ABS glass transition temperature (Tg) 100–105°C. https://www.sabic.com/en/products/polymers/acrylonitrile-butadiene-styrene-abs
- [6]LEGO Group, "LEGO Sustainable Materials" — ABS is the primary material used in LEGO brick manufacturing. https://www.lego.com/en-us/sustainability/materials
- [7]MatWeb Material Property Data — PLA Young's Modulus ~3.5 GPa; ABS Young's Modulus ~2.0 GPa. https://www.matweb.com/
- [8]MatWeb Material Property Data — PETG (Polyethylene Terephthalate Glycol-modified) tensile strength ~50 MPa. https://www.matweb.com/