Polylactic Acid (PLA), abbreviated as PLA, is the most commonly used material in FDM(Fused Deposition Modeling) as it’s affordable, stable and easy to print, which is a concord amongst 3D printing industry with regards to this fact. Polyethylene Terephthalate Glycol-modified(PETG), however, has become an increasingly popular material among 3D printing. In this article, a brief introduction shall be rendered with respect to PETG and PLA.
Definition and Characteristics of PETG
PETG is a common thermoplastic material in 3D printing, with its full name of Polyethylene Terephthalate Glycol-modified. It is a co-polymer modified material based on PET (Polyethylene Terephthalate) via introducing additional units into its molecular configuration. Glycol encompasses not only ethylene glycol but also various other diols. One of the commonly found diols in PETG is CHDM (1,4-Cyclohexanedimethanol). PETG inherits the excellent properties of PET, such as high strength, flame retardancy and chemical stability, while also improving the toughness and impact strength of PET.
PETG exhibits great mechanical characteristics, with high strength, toughness, and impact resistance that allow the printing of durable and impact-proof parts. These significant mechanical properties of PETG render it suitable for mechanical components, functional prototypes, and perdurable objects. In addition, PETG demonstrates admirable chemical stability. It shows strong resistance to corrosion from some solvents, acids, alkalis and other chemicals. Furthermore, PETG has good optical transparency, and thus it can print translucent and transparent parts. The optical transparency of PETG originates from its chemical composition and structure. PETG is a polyester material, and its molecular chains contain a large number of ester bonds and methylene groups, which themselves do not absorb visible light, making PETG good optical transparency and making it an ideal material for translucent and transparent parts. This is a unique advantage of PETG compared to other common 3D printing materials such as ABS and PLA. Besides, PETG material is considered food safe. It can be used to make food containers. However, stringing can be an issue that requires optimization of printing parameters. With proper settings, PETG can produce printed parts with an aesthetic surface finish and accurate dimensions.
PETG VS PLA Filament
A. Main difference between PETG and PLA
I.Material properties
PETG: PETG has high strength, great toughness and superior impact resistance, and can withstand large stresses and pressures. It also has good chemical resistance and heat stability, suitable for various applications.
PLA: PLA has lower strength and relatively inferior durability, suitable for some light-load and non-structural applications. It is a biodegradable material that is environmentally friendly.
| Mechanical properties | PLA | PETG |
| Tensile Strength | 61MPa | 61.4MPa |
| Elastic Modulus | 3500MPa | 2990MPa |
| Elongation at break | 3.1% | 5.3% |
| Izod impact strength | 32kJ/㎡ | 35kJ/㎡ |
II.Printability
PETG: PETG has a higher melting point and melt viscosity, thus requiring higher printing and hotbed temperatures. It is very prone to stringing during 3D printing. Some proper adjustment is requisite to ensure optimal results.
PLA: PLA has a lower melting point and melt viscosity and thus its printing temperature is lower than PETG. It is easy to print and suitable for most 3D printers, making it beginner-friendly.
III. Bio-degradability
PETG: PETG is not a bio-degradable material and degrades slowly in the natural environment. It may take a long time to decompose into natural substances.
PLA: PLA is a biodegradable material that can degrade rapidly and eventually decompose into natural substances. It is more environmentally friendly and suitable for disposable and short-term applications.
B. Pros and Cons of PETG
Advantages of PETG:
Strength and durability: PETG is stronger and more durable than PLA, and can undergo greater stress and impact loads.
Chemical resistance: PETG has better chemical resistance. The polymer PETG harbors a robust immunity to a myriad of corrosive compounds. Its chemical constitution confers resilience against the deleterious effects of particular caustic solutions and acidic or basic agents that would otherwise compromise its structural integrity.
Transparency: Due to its unique chemical composition and structure, PETG shows good optical transparency, making it
Heat stability: PETG has higher heat stability and can maintain shape and strength at high temperatures.
Easy formed: PETG is highly versatile, as it can be easily vacuum-formed or thermo formed and has the ability to withstand high pressures without any risk of cracking. It can be molded through injection into various shapes or extruded into sheets.
Recyclability: PETG can be recycled and reprocessed into new products, which is beneficial to the circular economy.
Disadvantages of PETG:
Non-biodegradability: PETG degrades slowly in the natural environment, is not biodegradable, and may potentially accumulate in the environment.
Water absorption: It exhibits a high degree of water absorption. PETG readily absorbs water if not stored properly. This will make parts more brittle.
Exacting printing requirements: Since PETG is more prone to stringing than PLA or ABS, you will have to experiment with retraction and bridging settings to get quality prints.
Advantages of PLA:
Easy to print: PLA is easier to print as its exhibits low shrinkage, well compatibility and great adhesion.
Biodegradability: PLA is a biodegradable material that can degrade rapidly and decompose into natural substances under appropriate conditions.
Environmentally friendly: PLA is made from renewable plant resources, relatively environmentally friendly, and reduces dependence on fossil fuels.
Low heat shrinkage: PLA has a relatively low heat shrinkage rate, which is beneficial for printing large models and reducing print distortion.
Disadvantages of PLA:
- Lower strength and durability: Compared with PETG, PLA has lower strength and durability, and is not suitable for applications requiring high strength.
- Low melting point: PLA's low melting point causes it to soften and deform easily in high temperature environments.
Why PETG can not repalce PLA and PLA+？
Based on the above comparison, it is evident that PETG outperforms PLA in various aspects. Not only is PETG often more affordable than PLA+, but it can even be cheaper than PLA itself. However, despite these advantages, PETG has not managed to replace PLA. The primary obstacle lies in the fact that PETG is more challenging to print and not very beginner-friendly.
Applications of PETG
Manufacturing Industry: PETG finds extensive applications in the manufacturing industry for producing industrial components and functional prototypes. Its high strength and durability make it suitable for manufacturing mechanical parts and fixtures. Moreover, PETG's chemical resistance allows it to be used in the production of components that come into contact with chemicals, such as pipes and valves served as chemical processing equipment.
Medical Field: Some PETG has excellent bio-compatibility and transparency that can be widely employed in the medical field. It can be used to manufacture medical devices, medical models, mask frames, test tube racks, and more. The bio-compatibility of some PETG makes it suitable for applications involving human contact, while its transparency provides clear visual observation.
Packaging Industry: PETG is extensively used in the packaging industry. It can be utilized to produce transparent packaging boxes, bottles, containers, and more. PETG's impact resistance and durability ensure the protection of packaged items from damage. Additionally, its chemical resistance allows for safe contact with various chemicals.
Creative Design: Due to its excellent transparency and dyeability, PETG unlocks the potential for the field of creative design. It can be used to create lampshades, decorative items and artworks. The versatility of PETG allows designers to achieve various shapes and complex structures.
Education Sector: PETG is a relatively safe material and can be employed in 3D printing education in schools and educational institutions. Students can use PETG to fabricate models, prototypes, and tangible displays, enriching their understanding of object structures and design principles.
Signage and Display: PETG is extensively utilized for point-of-sale retail stands and displays. Due to its ability to be easily tinted with transparent colors, it is also highly suitable for signage.
Tips for PETG - Printing
- Temperature: Considering the strength and surface aesthetics of the printed models, outcomes can significantly differ based on the specific 3D printer and filament utilized. In this context, it is essential to adhere to a fundamental principle:
a.For enhanced visual appeal, adjust the temperature accordingly. The PETG print temp is 230-240℃.
b.If the model necessitates increased strength, elevate the printing temperature.
- Cooling: PETG exhibits distinct cooling requisites. It should neither experience inadequate nor excessive cooling, as the latter may compromise layer adhesion. Varying machine specifications and fan requirements render it impractical to provide precise cooling intensity values. Consequently, the specific cooling parameters must be fine-tuned in accordance with real-world circumstances. Herein lies a guiding principle: while ensuring model robustness, maximize cooling intensity to attain the desired aesthetic outcome. For instance, if setting cooling at 100% significantly diminishes model strength, gradually reduce cooling intensity by 20%. Employing this approach, print a temperature tower to identify the optimal fan intensity.
- Retraction: Setting retraction parameters aims to solve stringing. Using SUNLU PETG as an example, 220 degrees Celsius constitutes the minimum temperature threshold for maintaining acceptable model strength. Printing a retraction testing tower is a good way to tackle stringing. Regular retraction of testing tower ranges generally span 1-3mm for proximate extruders and 4-10mm for remote extruders. In the case of noticeable stringing despite high retraction settings, consider increasing the retraction speed. Excessively high retraction values may leave minor blemishes on the model's surface and increase the risk of filament clogging.
- Bed adhesion: PETG exhibits rapid cooling, limited fluidity, and a proclivity for nozzle adhesion. Consequently, it is advisable to slightly increase the Z-axis offset by approximately 0.05mm. Alternatively, employing a glass bed in conjunction with PVP glue can bolster bed adhesion.
In conclusion, PETG is a material that combines the advantages of both ABS and PLA. It achieves a print quality similar to PLA while exhibiting the strength and durability of ABS. Furthermore, PETG has excellent transparency and heat resistance, meeting a variety of user needs. However, it should be noted that PETG places higher demands on printing techniques.
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