PLA (Polylactic Acid)
polymersemi-crystalline bio-derived thermoplastic polyester
Polylactic acidPolylactidePLA+PolyLite PLAUltimaker PLAESUN PLABio-PLA
Mechanical & thermal properties — 3 conditions
| Property | FDM as-built (XY) | FDM as-built (Z — upright) | FDM annealed (55°C / 1 h, XY) |
|---|---|---|---|
| Elastic modulus | 3–4 GPa | — | 3–4 GPa |
| Ultimate tensile strength | 50–65 MPa | 35–45 MPa | — |
| Elongation at break | 3.0–10.0 % | 1.0–6.0 % | — |
| Density | 1.22–1.26 g/cm³ | — | — |
| Glass transition (Tg) | 55–65 °C | — | — |
| As-built surface Ra | 6.0–18.0 µm | — | — |
Values shown as min–max where a spread is reported, otherwise as typical ± unit. Ranges reflect inter-source variation, not single-sample scatter. All values are for AM-processed specimens unless noted.
Engineering considerations
- Heat resistance is the decisive selection criterion. If the part will ever exceed 45°C under load (sun exposure, near electronics, automotive interior) — do not use standard PLA. Consider PETG (Tg ~80°C), ABS (Tg ~105°C), or ASA instead.
- Orientation strategy: maximise load-bearing in XY direction. Z-direction strength is 70–80% of XY. For critical cross-sections, flat-print with load in the horizontal plane. Wall thickness minimum 1.2 mm for structural parts; 0.8 mm possible for cosmetic features.
- Infill pattern and density drive structural properties more than material choice for FDM. At 20% gyroid infill, strength is ~30–40% of solid. Use 100% rectilinear infill in load-bearing cross-sections. Model hollow bodies with thick walls rather than high-infill solids for optimal stiffness-to-weight.
- Moisture management: PLA absorbs moisture during storage (Hygroscopic). Wet filament causes bubbles, stringing, poor layer adhesion, and reduced mechanical properties. Dry at 45–50°C for 4h before printing if stored >2 weeks unsealed. Vacuum-seal with desiccant for long-term storage.
- Post-processing: PLA cannot be smoothed with acetone (unlike ABS). Ethyl acetate vapour works but is flammable and requires extraction. For smooth surfaces: sand through 220→400→800→1200 grit then prime. Polyurethane or epoxy coating provides UV protection and sealing.
- Biodegradability in context: PLA only biodegrades in industrial composting facilities (55°C+, specific microorganism mix). It does not degrade in landfill, ocean, or home compost at a meaningful rate. The bio-derived carbon content reduces lifecycle CO₂ but part longevity is not guaranteed for outdoor applications.
- PLA+ grades: many suppliers offer 'PLA+' formulations with toughening additives (PBAT, TPU blends) that significantly increase impact resistance and elongation. These are proprietary blends — verify properties with supplier datasheet. Impact resistance can be 3–5× standard PLA at modest cost increase.
Advantages
- Easiest FDM material to print: sticks to build plate, minimal warping, no heated chamber needed, low odour
- Highest stiffness of common FDM polymers (~3.5 GPa): stiffer than PETG (~2.2 GPa) and ABS (~2.1 GPa)
- Bio-derived from renewable feedstock (corn starch, sugarcane): lower carbon footprint per kg vs petroleum-based polymers
- Industrially compostable (EN 13432 certified grades): meets EU single-use plastics legislation for some applications
- Wide filament ecosystem: available in every colour, diameter, and specialty blend (PLA+, metal-fill, wood-fill, carbon-fill)
- Dimensionally stable: low shrinkage during printing — easier to achieve dimensional accuracy than ABS
- Lowest cost of common FDM filaments — commodity grades available from ~£15–25/kg
- Good optical clarity in transparent grades; excellent surface finish achievable with sanding and painting
Limitations
- Very low heat resistance: HDT ~50–60°C at 0.45 MPa. Parts permanently deform in hot cars, near heating vents, or in direct sunlight
- Brittle: lowest impact resistance of the common FDM polymers. Snap-fits and impact-loaded parts require PETG or ABS instead
- UV degradation: PLA yellows and loses toughness with prolonged UV exposure. Not suitable for long-term outdoor use without UV-stabiliser coating
- Hygroscopic: absorbs moisture in storage, causing print quality problems (bubbles, stringing). Store in sealed containers with desiccant
- Not suitable for powder-bed fusion (SLS/MJF): insufficient thermal stability and unsuitable crystallisation kinetics
- Biodegrades in industrial composting conditions (not home compost) — may be a limitation for long-life product applications
- Low chemical resistance: attacked by ketones (acetone) and some esters; not suitable for chemical-contact applications
- Post-processing: acetone smoothing does NOT work on PLA (unlike ABS). Requires sanding or vapour smoothing with ethyl acetate
Typical applications
Visual prototypes, concept models, and display partsLow-stress functional parts at room temperatureEducational and hobby applications — most widely used consumer FDM materialPackaging prototypes and ergonomic handlesMedical device non-implantable mockups and anatomical modelsArchitectural models and scale modelsJigs and fixtures for room-temperature assembly operationsConsumer product housings and enclosures not exposed to heatEco-packaging: compostable in industrial compost facilities
Industries
consumerindustrialmedicalautomotive
Standards & certifications
iso-527-3-2018established
Tensile testing of plastics films and sheets — applicable to FDM PLA specimens
consumerindustrial
ISO 527-3:2018 for thin plastic films. ISO 527-2 Type 1B specimens are more commonly used for FDM test coupons.
Compatible AM processes (1)
Other polymer materials
PA12 (Polyamide 12)semi-crystalline thermoplastic polyamidePA12-CF (Carbon Fibre PA12)carbon fibre reinforced polyamide-12 compositePA11 (Polyamide 11)semi-crystalline thermoplastic polyamide (bio-based)PEEK (Polyether Ether Ketone)semi-crystalline high-performance aromatic thermoplasticPEKK (Polyetherketoneketone)semi-crystalline high-performance aromatic thermoplastic (PAEK family)ULTEM 1010 (Polyetherimide PEI)amorphous high-performance thermoplastic (polyetherimide family)PETG (Polyethylene Terephthalate Glycol)amorphous/semi-crystalline copolyester thermoplasticABS (Acrylonitrile Butadiene Styrene)amorphous engineering thermoplastic terpolymerTPU (Thermoplastic Polyurethane)elastomeric thermoplastic block copolymerPC (Polycarbonate)amorphous engineering thermoplastic polycarbonateASA (Acrylonitrile Styrene Acrylate)amorphous engineering thermoplastic terpolymerNylon PA6 / PA66 (Polyamide 66)semi-crystalline engineering thermoplastic polyamidePP (Polypropylene SLS/MJF)semi-crystalline thermoplastic polyolefinPEBA (Polyether Block Amide / TPA)thermoplastic elastomeric polyether block amide copolymer
Related calculators
Extrusion WidthActual extrusion width from nozzle diameter, layer height, and flow rate multiplier. Wall perimeter count from nominal thickness. FFF/FDM design rule compliance check.RoughnessTheoretical Ra and Rz from layer thickness and surface angle (staircase effect). Upward, downward, and vertical faces. LPBF, SLS, FDM, SLA, DED. Per Grimm et al.Dimensional AccuracyExpected dimensional deviation (mean bias ± 1σ) for XY and Z axes by process, material class, and geometry type. Based on aggregated published accuracy datasets. Answers: what tolerance can I realistically hold?Cost-Per-Part EstimatorMachine hourly + material + labor + post-processing → unit cost with margin. Currency-agnostic.
Last reviewed: 2026-05-13 · v1 · Sources: ultimaker-pla-datasheet-2022, song-2017-pla-fdm-params, iso-527-3-2018
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