Introduction to High-Performance Engineering Thermoplastics

Ever since their introduction in the 1970s, high-performance engineering thermoplastics have transformed industries ranging from aerospace and automotive to medical devices and electronics. Offering properties like heat resistance, strength and stiffness combined with manufacturability advantages over thermosets, these plastics opened up new possibilities for part and component design. Among the earliest members of this class of materials was polyetherimide (PEI), marketed under the trade name Ultem. While PEI established thermoplastics in demanding applications, one polymer was about to emerge and raise the bar even higher - Polyether ether ketone or PEEK.

The Discovery and Development of PEEK

First created in the U.K. in the late 1970s by Imperial Chemical Industries (ICI), Polyether Ether Ketone (PEEK)  is a semi-crystalline thermoplastic whose core molecular structure consists of aromatic ether ketone units. ICI filed the first patent for PEEK in 1981 and began marketing it under the brand name Victrex PEEK shortly after. Early research showed PEEK to have a unique blend of properties that exceeded other engineering resins available at the time. It exhibited extraordinary heat resistance up to 260°C, strong mechanical performance even at elevated temperatures, excellent chemical resistance and a self-extinguishing property. These attributes made PEEK highly suitable for applications in aerospace, automotive, oil & gas and medical industries.

PEEK Gains Widespread Adoption

As PEEK manufacturing processes improved to enable complex part production, its use expanded rapidly across multiple sectors in the late 1980s and 1990s. In aerospace, PEEK helped enable higher heat applications in areas like fastener joins, bushings and seals. Its combination of strength, stiffness and toughness also found roles in airframe components. The automotive industry took note for under-hood applications requiring heat resistance along with machinability. Medical implant manufacturers were drawn to PEEK’s biocompatibility and MRI compatibility. PEEK connectors helped enable downhole tools to operate reliably in extreme oil & gas environments as well.

Today, PEEK continues powering innovations by allowing the creation of high-performance parts and devices previously impossible or impractical to produce. With successful space on the International Space Station and proven track records across many industries, PEEK has established itself as a leading high-performance thermoplastic.

PEEK Processing Methods

While PEEK exhibits attractive properties, transforming it into net shape parts requires specialized processing know-how. Here are some of the prominent techniques used:

Injection Molding: Efficient for high volumes, injection molding PEEK involves elevated temperatures of 380°C or more along with specialized molds made from alloys like inconel or ceramics to withstand wear. Intricate parts for medical devices are a key application.

Machining: As a machinable engineering plastic, PEEK lends itself well to computer-numeric controlled (CNC) milling and turning. Close tolerances can be achieved.

3D Printing: Laser sintering and multi-jet fusion 3D printing allow geometrically complex PEEK parts to be built layer by layer for applications such as customized implants.

Extrusion: Continuously extruding PEEK into rods, tubes or profiles for subsequent machining is common for automotive and medical components.

Continued Innovation with PEEK Composites

To further augment properties and expand economic viability, PEEK is often reinforced with fibers. Glass-fiber reinforced PEEK (PEEK-GF) delivers enhanced stiffness, impact strength and machinability retention at elevated temperatures compared to unfilled PEEK. Carbon-fiber reinforced PEEK (PEEK-CF) provides additional strength and stiffness gains for structural parts. With the FDA clearing carbon fiber PEEK for implant use, its adoption is growing. Other fillers being investigated include Kevlar, ceramic and carbon nanotubes to achieve multifunctional composite blends. Overall, reinforced PEEK composites have strengthened this material platform’s relevance across high-tech sectors.

Applications Pushing the Boundaries of PEEK

As an engineering material with continuous property enhancements, PEEK keeps finding roles in new frontiers. Aerospace leverages its strength-to-weight and burn resistance for components like engine blades. Medical implants demand its MRI-compatibility and durability. Connectors in downhole drilling depend on its corrosion resistance. Electric vehicles need its heat deflection abilities. PEEK also shows promise for hydrogen fuel cell seals. Going forward, as additive manufacturing of high-performance plastics matures, digital optimization of PEEK parts at microstructures may further expand its design space. With properties still exceeding most other thermoplastics, PEEK will likely remain a keystone polymer driving technological advancement.

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