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PETG
(Polyethylene Terephthalate Glycol)
The Ultimate Balance of Unyielding Strength, Glass-Like Clarity, and Effortless Versatility.
Why 3D Print with PETG?
Benefits of PETG:
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High Impact Resistance: PETG is highly durable and flexible, making it significantly less brittle than standard PET or PLA. It can absorb impact without shattering.
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Excellent Clarity: It offers glass-like transparency, which is ideal for applications requiring see-through components, such as display cases, signage, or custom bottles. However, from our experience - Clarity can take a lot of practice!
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Chemical Resistance: It holds up exceptionally well against water, acids, and alkalis, making it a reliable choice for medical and food-safe environments.
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Ease of Fabrication: Whether thermoforming, bending, or 3D printing, PETG is highly workable. In 3D printing specifically, it exhibits minimal warping and shrinkage compared to materials like ABS.
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Odorless Printing: Unlike ABS, PETG does not emit strong or toxic fumes during the heating or melting process.
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Recyclability: It is fully recyclable (usually categorized under plastic recycling code #1), which appeals to environmentally conscious consumers.
A Few Drawbacks of PETG:
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Prone to Scratching: While impact-resistant, its surface is relatively soft and scratches easily compared to glass or acrylic.
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UV Sensitivity: Prolonged exposure to direct sunlight can weaken the material and cause it to become brittle over time, making it less ideal for permanent outdoor use. Use ASA if you are worried about Sun exposure.
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Hygroscopic Nature: PETG readily absorbs moisture from the air. If used in 3D printing, the filament must be stored in a dry environment; otherwise, moisture absorption will lead to poor extrusion, stringing, and weak layer adhesion.
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Printing Quirks (for 3D Printing): It is notorious for "stringing" (leaving fine hairs of plastic between gaps) and does not bridge over empty spaces as cleanly as PLA. But, we have printed with it a lot so understand how to minimize this.
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Environmental Persistence: While recyclable, it is still a petroleum-based plastic that will not naturally biodegrade if it ends up in a landfill.
PETG is a great 3D Printing material that we use a lot here at Outlaw Prototyping. It is strong, fairly inexpensive, and stands up to most applications for our clients prototypes. If you would like to discuss building your prototype in PETG, let us know!
PETG Tech Specs
PETG Mechanical Properties:
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Tensile Strength: 50 - 53 MPa (This measures how much pulling force the material can withstand before breaking)
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Tensile Modulus: ~ 2,050 MPa (This indicates the material's stiffness or resistance to deformation)
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Elongation at Break: 15 - 50% (This shows how much the material can stretch before breaking)
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Flexural Strength: 70 - 77 MPa (This measures the material's ability to resist bending)
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Flexural Modulus: ~ 2,100 MPa (This indicates the material's stiffness in bending)
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Hardness: ~ Shore D 70 (This measures the material's resistance to indentation)
PETG Thermal Properties:
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Glass Transition Temperature: ~ 80 °C (This is the temperature at which the material transitions from a rigid state to a more flexible state)
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Heat Deflection Temperature (1.8 MPa): 62 - 68 °C (This measures the material's resistance to deformation under heat and load)
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Melting Temperature: No true melting point (Amorphous), but extrudes at 220 to 250 °C
Other Properties
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Density: 1.23 - 1.27 g/cc
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Moisture Absorption: PETG is highly hygroscopic and absorbs moisture from the air, which can cause stringing, bubbling, and weak layer adhesion if not dried before printing.
When Should I Choose PETG Over PLA or ABS?
PETG is often described as the "Goldilocks" of 3D printing filaments because it sits perfectly between PLA and ABS. PLA is exceptionally easy to print and holds fine details beautifully, but it is rigid, brittle, and deforms at relatively low temperatures. ABS, on the other hand, is tough and highly heat-resistant, but it is notoriously difficult to print without a heated enclosure due to severe warping and toxic fumes.
You should choose PETG when you need the mechanical strength and durability of ABS without the associated printing headaches. It is the go-to material for functional parts that need to survive impacts, drops, or continuous stress, but don't necessarily need to survive the extreme temperatures of a car dashboard in the middle of summer. Because it barely warps during printing, it is also ideal for producing large, dimensionally accurate mechanical parts.
Conversely, you should stick to PLA if you only need a quick, highly detailed visual model or if you are printing complex geometries with steep overhangs, as PLA cools faster and bridges across gaps much cleaner. If your part will be subjected to high heat (exceeding 70°C), you will need to step up to ABS or ASA, as PETG will begin to soften and lose its shape.
Is PETG Tough Enough for Functional, Snap-Fit Prototypes?
Absolutely. PETG excels in functional prototyping precisely because it possesses a slightly lower flexural modulus than PLA, meaning it has a bit of natural "give." Instead of remaining rigidly stiff until it suddenly shatters under pressure, PETG will flex and deform before it breaks.
For snap-fit joints, living hinges, or interlocking mechanisms, this flexibility is crucial. When a plastic clip is pushed into place, it needs to flex over a lip and quickly snap back to its original position. PLA will often snap in half during this process because it cannot absorb the temporary stress, whereas PETG will stretch, slide into place, and recover its shape securely.
Additionally, PETG boasts exceptional layer adhesion. In 3D printing, the Z-axis (the vertical direction where layers stack) is usually the weakest point where parts split under a heavy load. Because PETG layers fuse together so strongly during extrusion, functional brackets, mechanical enclosures, and load-bearing fixtures printed in PETG are significantly more reliable than those made from stiffer, more brittle filaments.
How Does PETG Handle Chemical Exposure and the Elements?
PETG is highly resilient when it comes to environmental hazards, making it a favorite for industrial and workshop environments. It stands up incredibly well against a wide variety of chemicals, including weak acids, alkalis, oils, and greases. This chemical resistance means you can confidently use PETG for automotive fluid funnels, workshop organization containers, or protective casings for batteries and electronics.
It is also highly water-resistant. Unlike some materials that degrade or swell when exposed to moisture over long periods, printed PETG parts maintain their structural integrity and won't break down in damp environments. This makes it an excellent choice for hydroponics setups, custom aquarium plumbing, or indoor plant pots that require constant contact with water.
However, when it comes to permanent outdoor exposure, you must consider ultraviolet (UV) light. While PETG handles moisture and chemicals beautifully, prolonged exposure to direct sunlight will gradually degrade the plastic, making it brittle and prone to cracking over time. If your prototype or final part will live outside 24/7, you should either paint it with a UV-resistant clear coat or opt for a naturally UV-resistant material like ASA.
Can PETG Parts Be Sanded, Painted, or Glued?
Post-processing PETG requires a slightly different approach than other common plastics. While it can certainly be sanded and painted, its inherent toughness and chemical resistance make it a bit stubborn. Sanding PETG takes more elbow grease than PLA; because it has a lower melting point than ABS, it tends to soften and gum up the sandpaper if friction generates too much heat. Wet sanding is highly recommended to keep the surface cool and achieve a smooth finish.
When it comes to painting, PETG's slick, chemically resistant surface means paint struggles to adhere directly to the raw plastic. To get a professional finish, you must scuff the surface and use a plastic-adhesion promoter or an automotive primer before applying your base coats. Once properly primed, standard acrylics and spray paints will stick beautifully, allowing you to achieve a polished, presentation-ready model.
Gluing PETG also requires specific adhesives. Because it resists chemical solvents, traditional model glues (like plastic cement) or acetone—which melt and fuse ABS perfectly—will simply roll off PETG. Instead, you need mechanical adhesives. Cyanoacrylate (super glue), especially when paired with a chemical activator spray, works exceptionally well. For heavy-duty structural bonds, a two-part epoxy is your most reliable option.