Polyether ether ketone: latest developments and applications

Recent developments in additive manufacturing and materials science have enabled a rapid expansion of areas of application for PEEK, including the healthcare industry and the manufacturing of advanced composites.

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Since its commercialization in the 1980s, polyether ether ketone (PEEK) has become one of the most popular engineering thermoplastics, characterized by an unusual combination of high temperature performance, excellent mechanical strength and chemical resistance. exceptional.

Over time, the material has evolved and has been widely used in the aerospace, automotive, electrical and electronics industries.

PEEK is one of the most popular modern thermoplastic materials that is used in many manufacturing applications. It is a high performance semi-crystalline rigid polymer with a combination of unique properties, such as extremely high thermal, chemical and wear resistance.

Due to its high strength-to-weight ratio, PEEK is ideal for critical-weight aerospace applications. It is a material of choice for manufacturing electrical and electronic components due to its electrical insulating properties, and is widely used in chemical manufacturing applications that require long-term mechanical and chemical resistance.

High performance super polymer

Structurally, PEEK consists of alternating ketone and ether bonds. Although these bonds provide a degree of flexibility, PEEK is still considered a rigid polymer. Due to the rigid backbone of the aromatic polymer, the material exhibits some of the highest transition temperatures among commercial polymers, with a functional temperature range of up to 240°C.

Traditionally, PEEK is melt processed in the temperature range of 370-420°C by conventional methods, such as injection molding, extrusion and compression molding, facilitated by the presence of ether linkages in the polymer structure. By adjusting the processing conditions, manufacturers can relatively easily control the crystallinity of PEEK and its mechanical properties. However, PEEK processing is more expensive than other thermoplastics due to its high melting temperature of 343°C.

Why PEEK is becoming a material of choice for demanding applications

Nevertheless, the exceptional thermal, chemical and mechanical properties of PEEK, coupled with the fact that it is a weldable and machinable thermoplastic, have made this material a lightweight and economical substitute for stainless steel, aluminum and even tubing. titanium in the aerospace and oil/gas industries. PEEK is also used as a wear-resistant insulator in heavy-duty electrical wiring, while semiconductor manufacturing has shifted to using PEEK wafer carriers which provide better rigidity, better chemical resistance and minimal weight.

The chemically inert nature of PEEK, along with its resistance to wear and temperature, make it extremely well suited for biomedical applications. Initially, the material was used for the manufacture of diagnostic equipment and reusable medical devices. Over the past decade, several in vitro biocompatibility tests have revealed that PEEK exhibits no mutagenic or cytotoxic effects. As a result, PEEK has gradually been used as a biomaterial for orthopedic implants and prostheses.

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Over the past two years, considerable research effort has been directed towards combining the qualities of PEEK with the capabilities of additive manufacturing. Such a combination allows the creation of personalized implants and scaffolds with complex shapes and structures from a bioinert material capable of withstanding the harshest conditions.

Difficult material for 3D printing applications

PEEK 3D printing poses challenges that have only recently been overcome. For example, fused filament 3D printing technology requires extruders with an operating temperature of up to 450°C (much higher than the extrusion temperatures of other plastics like PLA and ABS). Additionally, the high viscosity of molten PEEK requires new extruder designs with optimized polymer flow. Proper cooling of printed materials is another critical aspect that must be considered when 3D printing PEKK to minimize shrinkage and packing of the final product.

The rapid development of 3D printing technology and the growing demand for high-temperature 3D printers have prompted companies like Roboze, Intamsys, Bond, Apium and others to produce increasingly affordable, larger and more efficient PEEK printers. easier to use for industrial production and rapid prototyping.

Development of PEEK as a biomedical material

More importantly, recently developed PEEK-based composite materials show enormous potential as 3D printing materials. New formulations in which organic (carbon fiber or fiberglass) or inorganic (hydroxyapatite) fillers are added to the PEEK filament make it possible to refine the mechanical properties of 3D printed biomaterials for orthopedics, reconstructive surgery of the column vertebral and bone fusion. 3D-printed PEEK composite biomaterials enable the development of personalized, patient-specific implants and prostheses with a precise fit that cannot be achieved by traditional materials and manufacturing practices.

In a recent study, 3D-printed PEEK implants were used as cartilage prostheses for the reconstruction of the rib cage skeleton as a replacement for natural cartilage that was removed during tumor extraction. These custom 3D-printed PEEK implants not only improve patient satisfaction and safety, but also allow surgeons to respond quickly to a wider range of patient cases.

Surface modifications and treatments of PEEK implants have already shown great promise in further improving the biocompatibility of the material. By adding osteogenic agents and improving the bioactivity of PEEK, scientists aim to improve the growth or bone growth of PEEK implants in the near future.

References and further reading

Verma, S. et al. (2021) Developments of PEEK (polyetheretherketone) as a biomedical material: a focused review. European Polymer Journal147, 110295. Available at: https://www.sciencedirect.com/science/article/abs/pii/S001430572100029X?via%3Dihub

Oladapo, BI, et al. (2021) 3D Printing of PEEK and its Composite to Augment Biointerfaces as a Biomedical Material – A Review. Colloids and B-Surfaces: Biointerfaces203, 111726. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0927776521001703?via%3Dihub

El Magri, A. et al. (2021) An overview of the influence of process parameters through the characteristic of 3D printed PEEK and PEI parts. High performance polymers, 33(8), 862-880. Available at: https://journals.sagepub.com/doi/10.1177/09540083211009961

Yu, Y.-H. and Liu, S.-J. (2021) Polyetheretherketone for orthopedic applications: a review. Current Opinion in Chemical Engineering, 32, 100687. Available at: https://www.sciencedirect.com/science/article/abs/pii/S2211339821000198?via%3Dihub

C. Schwaar (2021) PEEK 3D Printers – The Ultimate Guide [Online] All3dp.com Available at: https://all3dp.com/1/peek-3d-printer (Accessed February 9, 2022)

D. Maloney (2022) Extreme thermal mods for 3D printing exotic materials [Online] Hackaday.com Available at: https://hackaday.com/2022/01/19/extreme-thermal-mods-for-3d-printing-exotic-materials (Accessed February 9, 2022)

Rinaldi, M. et al. (2021) Polyether Ether Ketone (PEEK) Additive Manufacturing for Space Applications: A Nanosat Polymer Structure. Polymers, 1311. Available at: https://www.mdpi.com/2073-4360/13/1/11

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