Polyetheretherketone (PEEK) is a high-performance, semi-crystalline thermoplastic renowned for its exceptional combination of mechanical strength, thermal stability, chemical resistance, and biocompatibility. As a member of the polyaryletherketone (PAEK) family, PEEK maintains its properties under extreme conditions, making it a preferred material for challenging applications across industries like aerospace, automotive, electronics, and notably, medical device manufacturing. Its ability to replace metals while offering benefits like reduced weight and radiolucency drives its adoption in critical components manufactured through processes like injection molding, machining, and other precision manufacturing services.
PEEK possesses a unique set of characteristics that distinguish it as a leading engineering thermoplasticused in custom manufacturing solutions.
PEEK exhibits outstanding thermal stability, capable of continuous operation at temperatures up to 260°C (500°F). It retains a significant portion of its mechanical properties even at these elevated temperatures, far exceeding the capabilities of many other polymers. Its high glass transition temperature (around 143-150°C (289°F-302°F)) and melting point (around 343°C (649°F)) contribute to its dimensional stability under thermal load. This thermal resilience makes it suitable for applications involving steam sterilization or high-temperature operating environments.
PEEK offers impressive mechanical properties, including high tensile strength, stiffness (modulus), and hardness. It demonstrates exceptional resistance to creep (deformation under sustained load) and fatigue, ensuring long-term reliability in structural applications. Even unfilled grades maintain significant strength, while reinforced grades can achieve properties competitive with some metals. Its inherent toughness also provides good impact resistance.
This material displays broad resistance to a wide range of chemicals, including many organic solvents, oils, weak acids, and bases, even at elevated temperatures. It shows excellent resistance to hydrolysis, meaning it resists degradation from prolonged exposure to water and steam, a critical property for medical devices undergoing repeated sterilization cycles. While highly resistant, PEEK can be attacked by concentrated strong acids like sulfuric and nitric acid, and certain halogenated solvents.
Specific medical grades of PEEK, such as those produced by Victrex (PEEK-OPTIMA™) or Ensinger (TECAPEEK MT), have demonstrated great biocompatibility and are often certified to USP Class VI and ISO 10993 standards for medical device use, including for implants with body contact. PEEK is considered biologically inert, meaning it generally does not elicit harmful responses from the body. This property, combined with its mechanical attributes, makes it a popular choice for orthopedic, spinal, and dental implants.
Unlike metallic implant materials like titanium or stainless steel, PEEK is radiolucent, meaning it is transparent to X-rays and compatible with Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) scans. This allows for clearer post-operative imaging and assessment of surrounding tissues without the artifacts generated by metals.
PEEK exhibits impressive wear and abrasion resistance, coupled with a naturally low coefficient of friction. This makes it suitable for demanding tribological applications such as bearings, seals, gears, and sliding components, especially in high-temperature or chemically aggressive environments where traditional lubricants might fail. Modified grades incorporating fillers like PTFE, graphite, and carbon fiber further enhance these properties.
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PEEK's high performance profile enables its use in some of the most demanding applications across various sectors.
PEEK is extensively used in the medical field, particularly for implants due to its biocompatibility, bone-like modulus (reducing stress shielding compared to metal implants), and radiolucency. Common applications include spinal fusion cages, trauma fixation plates (often carbon-fiber reinforced), joint replacement components (like acetabular cups), dental implants (abutments, frameworks), and surgical instruments. Its ability to withstand sterilization methods like autoclaving, EtO, and gamma radiation is crucial. Medical injection molding is a key process for producing complex PEEK medical components with high precision.
In aerospace, PEEK's high strength-to-weight ratio, thermal stability, chemical resistance to jet fuels and hydraulic fluids, and inherent flame retardancy (low smoke and toxic gas emission) are highly valued. It is used for structural components, cable insulation, connectors, thermal acoustic blankets, and interior parts, helping to reduce aircraft weight and improve fuel efficiency.
Under the hood, PEEK components can withstand high temperatures, aggressive automotive fluids, and mechanical stresses. Applications include thrust washers, seal rings, bearings, gears, valve components, and sensor housings. Its wear resistance contributes to longer part life in demanding powertrain and transmission systems.
PEEK's chemical resistance and mechanical strength make it suitable for components in chemical processing, oil and gas exploration, and semiconductor manufacturing. Examples include pump components, valve seats, seals, bearings, downhole sensor housings, wafer handling equipment, and insulators. Its ability to operate in harsh chemical and high-temperature environments often extends equipment life and reduces maintenance.
With stable dielectric properties and low outgassing, PEEK is excellent for high-frequency electronics, semiconductor sockets, and cable sheathing—perfect for precision manufacturing solutions in the electronics sector.
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While neat PEEK offers exceptional performance, its properties can be further tailored through the incorporation of additives and reinforcements or via surface modification techniques.
Adding carbon fibers (CF) or glass fibers (GF) significantly increases PEEK's stiffness, strength, creep resistance, and thermal conductivity. Carbon fiber-reinforced PEEK (CFR-PEEK) offers maximum mechanical performance and is used in demanding structural use cases, including medical implants like trauma plates and spinal rods. Glass fiber-reinforced grades provide enhanced strength and stiffness at a lower cost than carbon fiber options.
For enhanced tribological performance, PEEK is often compounded with solid lubricants like Polytetrafluoroethylene (PTFE), graphite, and carbon fiber. These additives reduce the coefficient of friction and improve wear resistance, making these grades ideal for bearings, bushings, and seals operating under high loads or speeds, often without external lubrication.
While biocompatible, PEEK is considered bioinert, meaning it doesn't naturally integrate well with bone tissue (osseointegration). Research focuses on surface modifications to enhance bioactivity and encourage bone growth. Techniques include plasma spraying, creating porous structures, applying bioactive coatings (like hydroxyapatite), chemical etching, and incorporating bioactive materials directly into the PEEK matrix. Antimicrobial agents can also be added or coated to reduce infection risk.
By adding conductive fillers like carbon fibers or carbon nanotubes, PEEK's electrical properties can be modified from insulating to static dissipative or conductive, suitable for specific electronic or safety applications.
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Despite its numerous advantages, PEEK also has limitations that need consideration during material selection.
PEEK is significantly more expensive than commodity plastics and many engineering plastics. It is typically used in situations where its high performance characteristics are essential and cannot be met by lower-cost alternatives.
Due to its high melting point (around 343°C (649°F)), PEEK requires high processing temperatures for injection molding (typically 360-400°C (680°F-752°F) melt temperature) and extrusion. This necessitates specialized equipment capable of reaching and maintaining these temperatures accurately, potentially increasing manufacturing complexity and cost. Proper drying is also critical, as PEEK is hygroscopic and moisture can degrade it during processing.
PEEK has relatively low surface energy, which can make bonding or adhering other materials (like coatings or cements in dental applications) challenging without surface pre-treatment (e.g., plasma treatment, etching). Its inherent bioinertness, related to surface properties, can also be a drawback for implants requiring direct bone integration, necessitating modifications.
Like many high-strength plastics, PEEK can exhibit some sensitivity to sharp corners or notches, which can act as stress concentrators. Careful design considerations are needed to avoid sharp internal corners in load-bearing applications.
Choosing PEEK is often driven by the need for a material that can reliably perform in extreme conditions where other materials fail. Its unparalleled combination of high temperature resistance, robust mechanical properties, broad chemical inertness, excellent wear resistance, and proven biocompatibility makes it an invaluable asset in demanding sectors like medical, aerospace, and energy. While its cost and processing requirements are higher than many plastics, the long-term durability, reliability, and unique capabilities PEEK offers often provide significant value, enabling designs and applications that would otherwise be impossible. From lightweight metal replacement in aircraft to life-saving medical implants, PEEK delivers performance when it matters most.
At Aprios, we can help you choose the right PEEK material for your specific needs. Get in touch for expert advice and solutions tailored to your project!