What is PETG?
PETG (Polyethylene Terephthalate Glycol-modified) is a thermoplastic polyester that has become increasingly popular in the 3D printing community. To understand PETG, it helps to first know about its predecessor, PET (Polyethylene Terephthalate). PET is the same material used in water bottles and food containers. PETG is a modified version of PET, with glycol added during the polymerization process. This glycol modification prevents the material from crystallizing when heated, which gives PETG improved thermal properties and makes it more suitable for 3D printing.
At the molecular level, the glycol groups disrupt the regular pattern that would normally allow PET molecules to pack tightly together in crystalline structures. This disruption results in a more amorphous polymer with greater transparency, flexibility, and easier processing characteristics—all valuable traits for 3D printing applications.
History of PETG
The journey of PETG into 3D printing is relatively recent compared to materials like PLA and ABS, which dominated the early consumer 3D printing landscape. While PET itself was developed in the 1940s by chemists at DuPont, PETG modifications came later as manufacturers sought to improve PET's properties for various applications.
PETG began gaining traction in the 3D printing community around 2014-2015, as users searched for materials that combined the ease of printing found in PLA with the durability and temperature resistance closer to ABS, but without ABS's notorious warping and odor issues.
Companies like ColorFabb (with their "XT" filament) and Eastman Chemical Company were among the early promoters of PETG filaments for 3D printing. As desktop 3D printers became more capable of handling higher temperatures reliably, PETG steadily gained market share. By 2017-2018, PETG had established itself as the third major filament type in the consumer 3D printing market, offering a middle ground between PLA and ABS.
What are the advantages of PETG for 3D Printing?
PETG offers a remarkable combination of properties that make it attractive for many 3D printing applications:
Durability and impact resistance: PETG has excellent impact strength, significantly outperforming PLA in this regard. It can absorb shocks and impacts without cracking or shattering, making it suitable for functional parts.
Chemical resistance: PETG stands up well to many chemicals, acids, alcohols, and alkalis. This resistance makes it useful for parts that might come into contact with various substances.
Water resistance: Unlike materials like PLA that can degrade when exposed to moisture over time, PETG maintains its structural integrity even in humid conditions or when submerged.
Temperature resistance: PETG can withstand higher temperatures than PLA before deforming. With a glass transition temperature of around 80°C (176°F), PETG parts maintain their shape in moderately warm environments.
Food safety: Many PETG filaments are FDA approved for food contact, making them suitable for items like custom containers or kitchen gadgets. Always verify specific manufacturer claims about food safety.
Clarity and light transmission: PETG can be produced in highly transparent formulations, allowing for the creation of clear parts. This property is difficult to achieve with many other 3D printing materials.
Layer adhesion: PETG exhibits excellent layer adhesion, creating strong bonds between printed layers that enhance the overall strength of printed objects along their Z-axis.
Minimal warping: Compared to ABS, PETG has substantially less thermal shrinkage during cooling, resulting in less warping and better bed adhesion. This makes printing larger parts more reliable.
Low odor during printing: PETG emits minimal odors while printing, making it more pleasant to use in home environments compared to materials like ABS.
Recyclability: As part of the polyester family, PETG is recyclable (recycle code 1), though specialized facilities may be required for processing.
What are the disadvantages of PETG?
Despite its many positive attributes, PETG does have some limitations that users should consider:
Stringing and oozing: PETG has a tendency to string between separate parts of a print due to its slightly sticky nature when molten. This can require more post-processing work to clean up prints.
Surface scratching: While durable against impacts, PETG is somewhat prone to surface scratches compared to materials like ABS.
Moisture sensitivity: Though water-resistant once printed, PETG filament absorbs moisture from the air during storage, which can affect print quality. Proper storage in airtight containers with desiccant is recommended.
Stickiness to print surface: PETG can adhere so strongly to certain build surfaces that it might damage them upon removal or be difficult to remove without harming the print.
UV sensitivity: Extended exposure to ultraviolet light can cause PETG to yellow and become more brittle over time, though this happens more slowly than with many other plastics.
Print cooling challenges: PETG requires a careful balance of cooling—too much can weaken layer adhesion, while too little can result in poor overhangs and details.
Precise temperature requirements: PETG generally has a narrower optimal temperature range than PLA, requiring more precise temperature control for best results.
Post-processing limitations: Unlike ABS, which can be easily smoothed with acetone vapor, PETG lacks a simple chemical smoothing method to remove layer lines.
Higher cost: PETG typically costs more than standard PLA filament, though prices have been decreasing as its popularity increases.
3D Printer Requirements for PETG
Successfully printing with PETG requires certain printer capabilities:
Heated bed: While not always strictly necessary, a heated bed set to 70-90°C significantly improves first layer adhesion and reduces warping.
Hot end temperature capability: PETG typically prints at 230-250°C, so your printer must be able to reach and maintain these temperatures. Printers with all-metal hot ends are ideal but not essential.
Build surface considerations:
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Glass beds work well with PETG but should be used with a separator like glue stick to prevent the PETG from bonding too strongly
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PEI surfaces work excellently but may require a release agent
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BuildTak and similar surfaces generally work well with PETG
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Removable spring steel sheets coated with PEI are particularly useful for PETG as they allow for easy print removal by flexing
Part cooling fan: A controllable part cooling fan is important as PETG benefits from reduced cooling compared to PLA, typically running at 30-50% fan speed.
Enclosure (optional): While not strictly necessary (unlike ABS), an enclosure can help maintain consistent temperatures and improve print quality, especially for larger prints.
Filament path considerations: Due to PETG's slightly higher flexibility compared to PLA, direct drive extruders can provide more reliable feeding, though Bowden setups can work well with proper settings.
Material Properties of PETG
Bed Temp | 75-90°C |
Density | 1.23 g/cm3 |
Heated Bed | Required |
Coefficient of Thermal Expansion | 60 µm/m-°C |
Ultimate Strength | 53 MPa |
Extruder Temp | 230-250°C |
Printability | Very Easy |
Max Service Temp | 73°C |
Stiffness | Medium |
Durability | High |
How to Print with PETG - Tips and Tricks
To achieve the best results when printing with PETG, consider these practical tips:
Optimal print settings:
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Nozzle temperature: 230-250°C (start at 240°C and adjust based on results)
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Bed temperature: 70-90°C (80°C is a good starting point)
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Print speed: 30-60 mm/s (slower than PLA is generally better)
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Layer height: 0.1-0.3mm depending on the desired detail level
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Cooling: 30-50% fan speed after the first few layers
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Retraction: Slightly higher than PLA, typically 4-8mm for Bowden setups and 1-3mm for direct drive
Storage: Keep PETG filament in airtight containers with desiccant when not in use. If filament shows signs of moisture absorption (popping or hissing during printing), dry it at 65-70°C for 4-6 hours in a filament dryer or food dehydrator.
Common print issues and solutions:
Stringing:
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Increase retraction distance and speed
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Lower printing temperature by 5-10°C
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Enable "wiping" or "coasting" in your slicer if available
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Print a test tower to find optimal temperature
Poor bed adhesion:
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Ensure bed is properly leveled and at the correct temperature
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Use glue stick, hairspray, or specialized adhesives
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Slow down first layer speed to 10-20 mm/s
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Increase first layer width to 120-150%
Overhangs issues:
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Increase cooling for small overhangs while maintaining overall reduced cooling
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Design with support structures for angles greater than 45 degrees
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Consider printing a sacrificial tower nearby to allow more cooling time between layers
Z-banding or inconsistent extrusion:
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Check that filament is dry
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Ensure consistent filament diameter
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Clean nozzle regularly as PETG can sometimes cause more buildup than other materials
Finishing techniques:
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Sanding works well but requires progression through multiple grits
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Wet sanding can produce better results with PETG
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Paint adheres well, especially with appropriate primers
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For transparent prints, coating with clear epoxy can enhance clarity
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Heat guns can be used carefully to remove stringing (but with caution to avoid deforming the part)
Environmental Considerations of PETG
The environmental impact of PETG is an important consideration for environmentally conscious users:
Recyclability: PETG falls under recycling code 1 (same as PET bottles) and is theoretically recyclable. However, not all recycling facilities process PETG, and 3D printed items may have additives or colorants that complicate recycling.
Biodegradability: Unlike PLA, PETG is not biodegradable. It will persist in the environment for many decades if not properly disposed of or recycled.
Production footprint: The production of PETG requires petroleum resources, though less energy is typically used in its production compared to some other engineering plastics.
Reusability: Failed prints can potentially be reprocessed into new filament with appropriate equipment, though this may affect material properties.
Longevity considerations: PETG's durability means products last longer, potentially reducing the environmental impact of replacement cycles.
PETG vs. Other Common Filaments
To better understand PETG's place in the 3D printing material landscape, it's helpful to compare it directly with other popular filaments:
PETG vs. PLA:
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PETG is more durable, flexible, and temperature resistant than PLA
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PLA is easier to print, produces crisper details, and is more environmentally friendly
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PETG requires higher printing temperatures but offers better mechanical properties
PETG vs. ABS:
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PETG has better layer adhesion and less warping than ABS
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ABS has better heat resistance and is easier to post-process (acetone smoothing)
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PETG produces less odor and doesn't require an enclosure like ABS typically does
PETG vs. Nylon:
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Nylon is more flexible and has superior wear resistance compared to PETG
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PETG is easier to print and less hygroscopic than nylon
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Nylon requires much higher printing temperatures and typically an enclosed printer
PETG vs. TPU:
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TPU is significantly more flexible and elastic than PETG
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PETG provides better structural rigidity and is easier to print
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PETG offers better temperature resistance than most TPU variants
What is PETG-CF?
PETG Carbon Fiber is a composite filament made by blending PETG (Polyethylene Terephthalate Glycol) with carbon fiber. The addition of carbon fiber gives the filament enhanced properties, making it suitable for applications that require extra strength, rigidity, and resistance to wear. Here's a breakdown of what makes PETG Carbon Fiber unique:
Strength and Durability: Carbon fiber reinforcement makes PETG Carbon Fiber much stronger and stiffer than regular PETG. It has improved impact resistance and tensile strength, making it suitable for more demanding applications.
Lightweight: Despite the added carbon fibers, the filament remains lightweight, offering a strong material without adding too much weight to the final print.
Increased Rigidity: The carbon fiber gives the PETG filament better rigidity and structural stability, making it ideal for creating parts that need to maintain their shape under stress or heavy use.
Improved Print Quality: The addition of carbon fiber results in a matte, textured finish on printed parts, which can be aesthetically appealing. It also improves the surface finish of the final product by reducing visible layer lines.
Enhanced Thermal Resistance: PETG Carbon Fiber has a higher heat resistance than regular PETG, meaning it can withstand temperatures up to 70-80°C before softening, which makes it more durable in environments with moderate heat.
Improved Wear Resistance: The carbon fiber adds abrasion resistance, making PETG Carbon Fiber more durable in wear-prone areas like gears, bearings, and other moving parts.
Not right for you? Learn about other materials here.
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