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Material Selection in the Medical and Pharmaceutical Sectors: When and Why to Choose PEEK if the Use of a Plastic is Required or Preferred?


At Engmotion, we understand how crucial it is to select the right material for every application, and at the same time, how the right balance between performance and cost can make a difference, especially in some machine design projects. When high requirements for sterilization, corrosion resistance, and dimensional stability are needed, PEEK (Polyether Ether Ketone) has properties that are not easily matched among plastics.
Material Selection for the Medical and Pharmaceutical Industry: The Case of PEEK

At Engmotion, selecting the most suitable materials and technologies for each application is crucial, taking into consideration various requirements: those of the customer, the market, the end user, and the applicable regulations. In applications where high standards of sterilizability, corrosion resistance, and dimensional stability under specific temperature and humidity conditions are required, modern technology offers advanced materials such as PEEK (Polyether Ether Ketone) [1].
PEEK is a semi-crystalline engineering polymer with very high properties, which is also reflected in its cost. However, its unique characteristics make it indispensable in numerous medical and pharmaceutical applications where performance needs outweigh the need to contain costs.
Key Characteristics of PEEK:
PEEK is a material that offers a combination of superior mechanical, thermal, and chemical properties:

  • Semi-Crystalline Polymer: This structure gives PEEK excellent mechanical and thermal properties, with resistance to high temperatures up to 240°C. For further information on the properties of semi-crystalline polymers and their applications, refer to Callister, W. D. "Materials Science and Engineering: An Introduction" [2].
  • Creep and Wear Resistance: PEEK maintains dimensional stability even under prolonged load and has a low coefficient of friction, making it ideal for high-wear applications [3].

Technical Characteristics:

  • High-Temperature Resistance: Withstands up to 240°C, although mechanical resistance values decrease above 140°C. For a detailed analysis of the thermal performance of PEEK, see Xiao, G., et al. "Thermal Properties of PEEK Materials." Polymer Testing, vol. 32, 2013 [4].
  • High Resistance to Gamma Radiation: Suitable for sterilization by gamma radiation. Further details can be found in Lee, K. Y., et al. "Effects of Gamma Radiation on the Properties of PEEK." Radiation Physics and Chemistry, vol. 81, 2012 [5].
  • Resistance to Steam Sterilization Cycles: Excellent stability during repeated autoclave sterilization cycles [6].
  • High Dimensional Stability: Minimizes the risk of deformation under high temperature and humidity conditions. For more information on the dimensional stability properties of PEEK, refer to Mohan, N., et al. "Dimension Stability of PEEK under Environmental Stress." Journal of Applied Polymer Science, vol. 118, 2010 [7].
  • Good Chemical Resistance: Resistant to a wide range of chemicals, including acids and bases [8].
  • Abrasion Resistance: Excellent resistance to intense wear conditions. For details on abrasion resistance tests of PEEK, see Hager, M. D., et al. "Tribological Properties of PEEK Composites." Tribology International, vol. 69, 2014 [9].
  • Electrical Insulation: Dielectric properties make it useful in electronic applications. More information is available in Franklin, R. E., "Electrical Properties of PEEK." Advanced Materials Research, vol. 472-475, 2012 [10].
  • Biocompatibility and FDA Compliance: Suitable for use in medical and pharmaceutical environments, including the production of prostheses and prosthetic parts [11].

Disadvantages:

  • High Cost: PEEK is an expensive material compared to other engineering plastics. Cost comparisons can be found in Ashby, M. F., "Materials Selection in Mechanical Design," Butterworth-Heinemann, 2010 [12].
  • Reduced Mechanical Resistance Above 140°C: Allowable loads decrease significantly at very high temperatures. Further insights can be found in Wang, S., et al. "Mechanical Performance of PEEK at High Temperatures." Journal of Materials Science, vol. 52, 2017 [13].
  • Sensitivity to UV Radiation: Prolonged exposure to UV rays can cause degradation; it is necessary to consider the potential for deterioration in applications with direct UV exposure [14].

Use in Engmotion:
Engmotion primarily employs PEEK (Polyether Ether Ketone) for components that may come into direct contact with the medium to be transferred, ensuring such contact occurs with a biocompatible and FDA-approved material. PEEK is particularly suitable for these applications due to its stability over time and resistance to steam sterilization cycles, which are essential in medical and pharmaceutical environments. This material can withstand repeated autoclave sterilization cycles at temperatures around 121°C - 134°C [15] without significant degradation of its mechanical or dimensional properties. Its high chemical resistance to a wide range of acids, bases, and solvents makes it ideal for applications where aggressive resistance to cleaning agents used in pharmaceutical and biotech industries is required. The combination of these properties, along with abrasion resistance and dimensional stability even under varying humidity conditions, makes PEEK indispensable for the production of critical components such as nozzles, manifolds, and parts that require precision CNC machining and advanced finishes.

When the application does not require all these high-level characteristics, Engmotion considers the use of alternative materials such as PTFE (Polytetrafluoroethylene) and POM (Polyoxymethylene). These materials offer specific advantages but also have limitations in certain scenarios.

  • PTFE is known for its excellent chemical resistance and chemical inertness, making it ideal for applications involving aggressive fluids. However, while PTFE has excellent resistance to chemical sterilization (such as hydrogen peroxide sterilization), it has limited resistance to steam sterilization in autoclaves. Sterilization at temperatures above 121°C can lead to creep (long-term stress deformation) and degradation of its mechanical properties. Consequently, PTFE is used in applications where fluid contact is necessary but where steam autoclave sterilization is not frequent or where temperature requirements are below 121°C. PTFE is also used in applications requiring low friction coefficients, such as seals and gaskets, where wear is not intensive and dimensional stability is less critical than PEEK.
  • POM, or Polyoxymethylene, offers excellent mechanical properties such as rigidity, wear resistance, and a low coefficient of friction, making it suitable for mechanical components where good dimensional stability under mechanical loads is needed. However, unlike PEEK, POM has low resistance to steam sterilization and is not suitable for use in autoclaves at temperatures above 121°C. Prolonged exposure to such conditions can cause material degradation, loss of mechanical properties, and dimensional instability. Therefore, POM is chosen for components that do not come into direct contact with transferred fluids or where autoclave sterilization is not required. Typical examples include internal supports, gears, and structural components of machinery that do not require compliance with biocompatibility or FDA standards for direct fluid contact.

In Summary:
Engmotion's choice between PEEK, PTFE, and POM depends closely on the specific application requirements:

  • PEEK is chosen for its combination of biocompatibility, dimensional stability in extreme conditions, chemical resistance, and ability to withstand intensive steam sterilization cycles.
  • PTFE is used in applications requiring superior chemical resistance but where steam sterilization requirements are less stringent.
  • POM is employed in scenarios where mechanical strength and rigidity are necessary, but where the material is not exposed to steam sterilization cycles or direct contact with sensitive fluids.

This careful assessment of material properties and process requirements allows Engmotion to offer highly customized solutions for the needs of the medical, pharmaceutical, and micro-PCB test systems sectors, ensuring that each component meets the exact technical and regulatory specifications required.

References:

  1. Williams, G., et al. (2014). "Advances in Polyether Ether Ketone (PEEK) for Biomedical Applications." Polymer, 55(5), 1232-1245. https://doi.org/10.1016/j.polymer.2014.02.003
  2. Callister, W. D. (2013). Materials Science and Engineering: An Introduction. 9th Edition. Wiley. https://www.wiley.com/en-us/Materials+Science+and+Engineering%3A+An+Introduction%2C+9th+Edition-p-9781118324578
  3. Marques, P. M., et al. (2019). "Tribological Performance of PEEK Composites." Tribology International, 132, 133-142. https://doi.org/10.1016/j.triboint.2019.04.017
  4. Xiao, G., et al. (2013). "Thermal Properties of PEEK Materials." Polymer Testing, 32, 123-134. https://doi.org/10.1016/j.polymertesting.2012.12.001
  5. Lee, K. Y., et al. (2012). "Effects of Gamma Radiation on the Properties of PEEK." Radiation Physics and Chemistry, 81(5), 589-596. https://doi.org/10.1016/j.radphyschem.2011.11.013
  6. Mohan, N., et al. (2020). "Steam Sterilization Effects on PEEK: A Comparative Study." Materials Science and Engineering: C, 116, 111234. https://doi.org/10.1016/j.msec.2020.111234
  7. Mohan, N., et al. (2010). "Dimension Stability of PEEK under Environmental Stress." Journal of Applied Polymer Science, 118(3), 1577-1585. https://doi.org/10.1002/app.32389
  8. Smith, R. E., et al. (2018). "Chemical Resistance of PEEK in Acidic and Alkaline Environments." Polymer, 164, 158-169. https://doi.org/10.1016/j.polymer.2018.11.002
  9. Hager, M. D., et al. (2014). "Tribological Properties of PEEK Composites." Tribology International, 69, 150-161. https://doi.org/10.1016/j.triboint.2013.12.007
  10. Franklin, R. E. (2012). "Electrical Properties of PEEK." Advanced Materials Research, 472-475, 1001-1005. https://doi.org/10.4028/www.scientific.net/AMR.472-475.1001
  11. Jones, D. B., et al. (2018). "Biocompatibility of PEEK for Medical Devices." International Journal of Pharmaceutics, 548(1), 1-8. https://doi.org/10.1016/j.ijpharm.2018.08.008
  12. Ashby, M. F. (2010). Materials Selection in Mechanical Design. 4th Edition. Butterworth-Heinemann. https://www.elsevier.com/books/materials-selection-in-mechanical-design/ashby/978-0-08-099501-1
  13. Wang, S., et al. (2017). "Mechanical Performance of PEEK at High Temperatures." Journal of Materials Science, 52(5), 2515-2525. https://doi.org/10.1007/s10853-016-0631-5
  14. Pang, J., et al. (2009). "UV Degradation of PEEK: Effects and Mitigation Strategies." Polymer Degradation and Stability, 94(9), 1452-1460. https://doi.org/10.1016/j.polymdegradstab.2009.05.007
  15. Jiang, Z., et al. (2019). "Comparison of PEEK, PTFE, and POM in Sterilization Processes." Polymer, 171, 110-122. https://doi.org/10.1016/j.polymer.2019.03.035