Post written by: Amber Jin
1. Introduction
Polyethylene terephthalate glycol (PETG) stands out as a Glycol Modified iteration of PET, a material commonly recognized for its ubiquitous presence in water bottles. This thermoplastic polyester boasts exceptional chemical resistance, durability, and impressive formability, making it a versatile choice for manufacturing applications. Notably, PETG's low forming temperatures facilitate seamless vacuum, pressure-forming, and heat-bending processes (Ksawery et al., 2017). In the realm of additive manufacturing, PETG filament emerges as a preferred build material, particularly prized in the domain of Fused Deposition Modeling (FDM) printers. This paper delves into the intrinsic material properties of PETG, explores its pivotal role in clinical applications through sterilization methods, and culminates in an exploration of the filament's printing processes.
Figure 1: Image of Novus PETG filament.
2. Material Property
Properties of a material determine the usage and application of it. This section will introduce material properties of PETG from two aspects, mechanical property and other properties.
2.1 Mechanical property
According to the experiment conducted by Ksawery et al.(2017), the specimens series with of 5A 5mm thick, Z-PETG and printed in flat direction have the mean value of Young’s Modulus, 5.9 GPa, and median value of Young’s modulus, 6.3 GPa. These values indicate the stiffness of PETG and its ability to resist deformation under load. Moreover, the tensile strength of PETG is a critical mechanical property that determines its resistance to breaking under tension (Ksawery et al., 2017). PETG exhibits a tensile strength in the range of 55-75 Mpa, highlighting its robustness and suitability for structural applications. Additionally, the impact strength of PETG is typically in the range of 5-20 kJ/m², making it a durable material for applications where impact resistance is crucial. Furthermore, the flexural strength of PETG, which measures its resistance to bending, is an essential mechanical property (Ksawery et al., 2017). PETG typically demonstrates a flexural strength of 70-90 MPa, showcasing its ability to maintain structural integrity under bending forces (Ksawery et al., 2017).
Figure 2: PETG specimens testing result of Young’s Modulus (Ksawery et al., 2017).
In conclusion, PETG is a miscible, transparent thermoplastic with excellent tensile strength and flexibility. The mechanical properties of PETG, including its Young’s Modulus, tensile strength, impact strength, and flexural strength, position it as a versatile material suitable for a wide range of applications in various industries.
2.2 Other Properties
After extensive investigation, Mercado-Colmenero et al. (2020) demonstrated that in numerical simulations, FFF-produced PETG may be considered as an isotropic material. The properties of PETG are crucial for its performance and applications. PETG is even more flexible and temperature resistant than Polylactic Acid (PLA). It can endure temperatures up to 75 degrees Celsius, and its qualities are not impacted by ultraviolet light. (Grzelak et. al., 2021). PETG also exhibits excellent chemical resistance and durability, making it resistant to a wide range of chemicals, including acids, alkalis, and solvents. This property makes PETG suitable for applications where exposure to harsh chemicals is a concern, such as chemical storage containers and laboratory equipment.
Furthermore, PETG is known for its low moisture absorption rate, which contributes to its dimensional stability and resistance to environmental factors. The low moisture absorption of PETG also makes it suitable for applications requiring hygienic conditions, such as food packaging and medical devices.
To conclude, such features of PETG enable easier disinfection using high temperatures or alcohols, making it more adaptable to medical solutions than other regularly used materials in medical additive manufacturing.
3. Sterilization
Sterilization of 3D printing materials can be typically performed in two ways: 1) Thermal sterilization with dry heat or steam, also known as wet heat sterilization or autoclave; 2) Low-temperature sterilization with chemicals such as ethylene oxide (EtO) or hydrogen peroxide or radiation with either ionizing or UV light (Oth et al., 2019). The conventional thermal steam sterilization at temperatures of 121 degrees Celsius or higher with significant rates of humidity may lead to deformation of PETG during the sterilization process, owing to its low melting temperature. This is because hydrolytic and thermal degradation have undermined the integrity of the polymer matrix. The time lapse between the production and actual usage of surgical tool may cause major changes to the tensile and flexural characteristics of PETG, in turn altering the surgical tool's overall structure and functionality (Fuentes et al., 2022). Compared to thermal sterilization, morphological deformations caused by EtO and Gamma radiation sterilization are submillimeter, which means their morphological variations less than 0.2mm. Thus, the low temperature sterilization method of PETG is much more suitable for surgical usage (Oth et al., 2019).
4. Clinical Application
PETG filament finds diverse applications in clinical settings due to its unique properties. In the medical field, PETG is commonly used for manufacturing medical equipment, prosthetics, surgical models, and other healthcare-related products. The biocompatibility of PETG makes it suitable for direct contact with skin and tissues, without causing adverse reactions or sensitivities.
4.1 Dental Application
PETG is often deployed in dental applications due to its biocompatibility and durability. Because PETG has a glass transition temperature (Tg) of about 80°C, it may be handled more easily and has characteristics similar to glass (Bichu et al., 2023). In orthodontic applications, the complementary characteristics of PET and PETG, with PET being rigid and crystalline and PETG flexible and amorphous, create a harmonious blend for orthodontic appliances. These materials excel in producing clear aligners due to their optical properties that facilitate efficient light transmission and reflection, ensuring clear visibility of teeth during treatment as shown in Figure 3 below. Research conducted by Iijimia et al. (2015). indicates that PETG, represented by Duran, maintains stable mechanical properties and shape memory even under varying temperatures, withstanding intraoral conditions up to 57°C. Studies further demonstrate PETG’s durability through numerous thermocycles and prolonged wear, highlighting its resilience and stability in dental applications, making it a reliable choice for long-term orthodontic treatments.
Figure 3: The methodical creation of three-dimensional direct-print clear aligners (Bichu et al, 2023)
4.2 Optometry Applications
The patient needs to provide precise measurements for the corrective lenses for prescription glasses to be manufactured. Reliable measurement tools have been developed to support the production process to obtain these measurements. Measurement devices can be made by stereolithography, fused deposition modeling, laser sintering, and plastic injection (FDM). Thermoplastic materials like PETG have drawn attention due to their ability to produce precise measurement instruments for lens fabrication, especially with the current improvements in FDM technology. PETG can be extruded using FDM technology to deposit layers of material and create these measuring mechanisms as needed as shown in the Figure 4 below (Constantin et al., 2023).
Figure 4: An image of general mechanism (side and isometric views) to obtain measurements for construction of lens.
4.3 Surgical Applications
The integration of 3D printing technology has revolutionized the rapid manufacturing of tailor-made surgical instruments, presenting a promising advancement that could enhance physicians' ability to address the unique pathophysiology of individual patients effectively. A predominant challenge associated with employing PETG for crafting surgical tools lies within the vulnerability of the polymer matrix to degradation when subjected to moist heat during the sterilization procedure (Fuentes et al., 2022). The prevalent reliance on traditional sterilization methods by the majority restricts the widespread adoption of PETG in surgical settings. Consequently, there has been a growing focus on developing disposable surgical instruments as a viable alternative.
4.4 Prosthetic Application
Although the myoelectric prosthetics nowadays are expensive, it is difficult for mechanical ones to offer same mobility and flexibility. 3D printed mechanical prosthetics provide a new solution for this problem, which can be designed and customized for the patients. Additionally, the material needs to be lightweight, easy to wear, and well-tolerated when it comes into direct touch with the patient's skin. After comparing price, versatility, durability and mechanical strengths of different 3D printing filaments material, PETG has been shown with prior mechanical strength to stand weight and forces as well as its lower cost and better availability (Desai et al., 2021). The PETG can also combined with other materials to enhance its properties. For example, a carbon-fiber reinforced PETG composite material (PETG-CF15) was found to provide a topology optimized design that coupled compressive strength with movement-permitting critical areas, resulting in a customized ortho-brace for an experimental ankle-foot orthosis as shown in the Figure 5 below (Steck et al., 2023).
Figure 5: The topology optimized PETG-CF15 leg splint. (a) perspective view; (b) wear on the foot.
5. 3D Printing Properties
In the realm of 3D printing, PETG filament emerges as a standout choice, distinguished by a set of unique properties essential for successful printing processes. Notably, PETG showcases exceptional chemical and impact resistance, ensuring the durability of printed objects in various applications. Its commendable thermal stability further enhances its printing capabilities, guaranteeing consistent performance throughout the printing process. Moreover, PETG is recognized as a food-safe material, broadening its utility across industries (Trhlíková et al., 2016). In addition, with an extrusion temperature range of 220-260 °C, PETG offers a precise thermal profile ideal for achieving high-quality prints. Operating at a moderate printing speed of about 40-60 mm/s, PETG strikes a balance between efficiency and print quality. To prevent warping issues, it is crucial to maintain the print bed temperature at approximately 80 °C, as exceeding this threshold can adversely impact the final print quality because of its low melting point (Trhlíková et al., 2016). These inherent properties position PETG as a versatile and reliable filament choice in the realm of 3D printing, catering to a diverse array of printing needs with consistent performance and quality outcomes.
PETG stands out as a preferred material for 3D printing owing to its notable strengths, including high impact resistance, absence of odor in emissions, and commendable thermal stability. Despite these merits, PETG exhibits certain drawbacks when compared with other filaments, for example, Acrylonitrile Butadiene Styrene (ABS). One significant limitation lies in PETG's high hygroscopicity, rendering it challenging to store adequately. Furthermore, a notable constraint of PETG pertains to its poor paintability, presenting difficulties, if not insurmountable obstacles, in achieving satisfactory paint adhesion on PETG surfaces (Trhlíková et al., 2016). The Table 1 below has shown the advantages and limitations of PETG 3D printing filament compared with other filaments, including ABS, Thermoplastic polyurethanes (TPU) and PLA.
Property | PETG | ABS | TPU | PLA |
Fumes | Non-toxic (proper ventilation is still required) | Toxic | Non-toxic (proper ventilation is still required) | Non-toxic (proper ventilation is still required) |
Hygroscopic | Yes | Yes | Yes | Yes |
Heated bed temperature (degree Celsius) | 70-80 | 80-110 | 60-90 | 20-60 |
Melting temperature (degree Celsius) | 220-260 | 210-250 | 190-245 | 180-230 |
Biodegradable | No | No | No | Yes |
Strength Resistance | Very good (but prone to scratches) | Good | Very good | Medium |
Recyclable | Yes | Yes | Yes | Yes |
Table 1: 3D printing properties of PETG and other materials.
6. Conclusion
In conclusion, the versatility and unique properties of PETG filament make it a compelling choice for various applications in the medical, dental, optometry, surgical, and prosthetic fields. Its biocompatibility, durability, and thermal stability render it suitable for manufacturing a wide range of products, from orthodontic appliances and clear aligners to surgical instruments and prosthetics. Despite its strengths in 3D printing, including high impact resistance and food safety, PETG does have limitations such as high hygroscopicity and poor paintability when compared to other filaments like ABS.
The research presented underscores PETG's significance in advancing healthcare technologies and improving patient outcomes through innovative applications. While PETG offers numerous benefits, ongoing research and development efforts are necessary to address its limitations and enhance its utility in diverse settings. By leveraging the strengths of PETG and exploring composite materials like PETG-CF15, there is potential to further optimize its properties for specialized applications. Overall, the findings highlight PETG's potential as a reliable and efficient material in the realm of 3D printing and medical device manufacturing, paving the way for continued advancements in healthcare technology and patient care.
7. References
Bichu, Y. M., Alwafi, A., Liu, X., Andrews, J., Ludwig, B., Bichu, A. Y., & Zou, B. (2023). Advances in orthodontic clear aligner materials. Bioactive Materials, 22, 384-403. https://doi.org/10.1016/j.bioactmat.2022.10.006
Constantin, V., Besnea, D., Gramescu, B., & Moraru, E. (2023). Aspects related to the design and manufacturing of an original and innovative marker support system for use in clinical optometry. Applied Sciences, 13(5), 2859. https://doi.org/10.3390/app13052859
Desai, R., Kelly, K., Lewis, K., Sreenivasan, V., Austin, W., Dinh, C., Labazzo, K., & Nicholas, C. (2021). The eagle hand: Innovations in 3D printing prosthetic hands. 2021 IEEE MIT Undergraduate Research Technology Conference (URTC). https://doi.org/10.1109/urtc54388.2021.9701613
Durgashyam, K., Indra Reddy, M., Balakrishna, A., & Satyanarayana, K. (2019). Experimental investigation on mechanical properties of PETG material processed by fused deposition modeling method. Materials Today: Proceedings, 18, 2052-2059. https://doi.org/10.1016/j.matpr.2019.06.082
Fuentes, J. M., Arrieta, M. P., Boronat, T., & Ferrándiz, S. (2022). Effects of steam heat and dry heat sterilization processes on 3D printed commercial polymers printed by fused deposition modeling. Polymers, 14(5), 855. https://doi.org/10.3390/polym14050855
Grzelak, K., Łaszcz, J., Polkowski, J., Mastalski, P., Kluczyński, J., Łuszczek, J., Torzewski, J., Szachogłuchowicz, I., & Szymaniuk, R. (2021). Additive manufacturing of plastics used for protection against COVID19—The influence of chemical disinfection by alcohol on the properties of ABS and PETG polymers. Materials, 14(17), 4823. https://doi.org/10.3390/ma14174823
Iijima, M., Kohda, N., Kawaguchi, K., Muguruma, T., Ohta, M., Naganishi, A., Murakami, T., & Mizoguchi, I. (2015). Effects of temperature changes and stress loading on the mechanical and shape memory properties of thermoplastic materials with different glass transition behaviours and crystal structures. The European Journal of Orthodontics, 37(6), 665-670. https://doi.org/10.1093/ejo/cjv013
Mercado-Colmenero, J. M., La Rubia, M. D., Mata-Garcia, E., Rodriguez-Santiago, M., & Martin-Doñate, C. (2020). Experimental and numerical analysis for the mechanical characterization of PETG polymers manufactured with FDM technology under pure uniaxial compression stress states for architectural applications. Polymers, 12(10), 2202. https://doi.org/10.3390/polym12102202
Oth, O., Dauchot, C., Orellana, M., & Glineur, R. (2019). How to sterilize 3D printed objects for surgical use? An evaluation of the volumetric deformation of 3D-Printed Genioplasty guide in PLA and PETG after sterilization by low-temperature hydrogen peroxide gas plasma. The Open Dentistry Journal, 13(1), 410-417. https://doi.org/10.2174/1874210601913010410
Steck, P., Scherb, D., Witzgall, C., Miehling, J., & Wartzack, S. (2023). Design and additive manufacturing of a passive ankle–foot orthosis incorporating material characterization for fiber-reinforced PETG-CF15. Materials, 16(9), 3503. https://doi.org/10.3390/ma16093503
Szykiedans, K., Credo, W., & Osiński, D. (2017). Selected mechanical properties of PETG 3-D prints. Procedia Engineering, 177, 455-461. https://doi.org/10.1016/j.proeng.2017.02.245
Trhlíková, L., Zmeskal, O., Psencik, P., & Florian, P. (2016). Study of the thermal properties of filaments for 3D printing. AIP Conference Proceedings. https://doi.org/10.1063/1.4955258
Yan, C., Kleiner, C., Tabigue, A., Shah, V., Sacks, G., Shah, D., & DeStefano, V. (2024). PETG: Applications in modern medicine. Engineered Regeneration, 5(1), 45-55. https://doi.org/10.1016/j.engreg.2023.11.001
Comments