How to Choose the Right Grade of Polyether Ether Ketone (PEEK)

Polyether ether ketone (PEEK) is a high-temperature polymer renowned for its outstanding mechanical, thermal, and chemical properties. It is widely used in aerospace, automotive, medical, and electronics industries.

But what sets PEEK apart from other high-performance plastics? Why do engineers choose PEEK over alternatives?

In this guide, we’ll explain how PEEK is manufactured and its molecular structure, and help you select the ideal PEEK grade for your applications.

What Is PEEK Plastic?

PEEK belongs to the polyaryletherketone (PAEK) family, which includes PEK, PEEK, PEEKK, PEKK, and PEKEKK. Among these, PEEK is the most widely used and produced on a large scale.

The abbreviation PEEK reveals its chemical backbone:

• Poly: many repeating units (polymer)
• Ether: an oxygen linkage in the chain
• Ether: another oxygen linkage
• Ketone: a carbonyl group (C=O) linkage

This specific arrangement gives PEEK its exceptional properties. Since commercialization in the early 1980s by Imperial Chemical Industries (ICI, now part of Victrex PLC), PEEK has been fully recyclable.

Performance Comparison with Other High-Temperature Polymers

Physical Properties

• Semi-crystalline, high-performance engineering thermoplastic
• Excellent resistance to liquids and fatigue
• Insoluble in common solvents and hydrolysis-resistant
• Can withstand steam or high-pressure water for 1,000 hours without degradation
• High dimensional stability, inherent purity, and biocompatibility

Mechanical Properties

• Excellent tensile strength, toughness, and creep resistance
• Balanced flexural and tensile properties for high-load, high-temperature applications
• Retains flexural modulus at very high temperatures
• Lightweight components suitable for harsh environments

Thermal Properties

• High melting point (Tm): 343°C
• High glass transition temperature (Tg): 143°C
• Continuous-use temperature: up to 260°C

Electrical Properties

• High volume and surface resistivity
• Excellent insulating performance across a wide temperature range

Flammability

• V0 flame rating at 1.45 mm thickness
• Limiting Oxygen Index (LOI): 35%
• Low smoke and toxic gas emissions

Reinforced Materials

• Glass or carbon fibers improve flexural modulus, creep resistance, thermal conductivity, and heat distortion temperature
• Carbon fiber-reinforced PEEK maintains performance at 299°C with tensile strengths up to 29,000 psi (~200 MPa)

PEEK vs. Other High-Temperature Polymers

• Fluoropolymers: PEEK excels in tensile strength, heat distortion temperature, operating temperature, adhesion, processability, and toxic gas emissions; slightly lower in chemical resistance, cost, toughness, and UV resistance.
• Polyphenylene Sulfide (PPS): PEEK has superior heat resistance, toughness, and flash control.
• Polyethersulfone (PES): PEEK offers better temperature performance, wear resistance, chemical resistance, and fatigue resistance.

PEEK generally isn’t blended with other polymers but can form miscible blends with other PAEKs and polyetherimides (PEI).

• PEEK/PEI blends: higher Tg
• Blends with PES and PPS: high compatibility

Limitations of PEEK

• High cost – best for high-performance applications
• Requires high-temperature processing
• Vulnerable to concentrated sulfuric, nitric, and chromic acids
• Susceptible to halogens and sodium
• Low UV resistance

Applications of Polyether Ether Ketone (PEEK)

PEEK is used across aerospace, automotive, electrical, medical, chemical, and engineering industries. Typical components include bearings, piston parts, pumps, HPLC columns, compressor valves, and cable insulation.

Automotive Industry

• Lightweight, noise-reducing, and functionally integrated alternative to metals
• Excellent dry/lubricated surface interaction, mechanical performance, fatigue resistance
• Applications: piston unit seals, gaskets, bearings, and moving parts in transmissions, brakes, and AC systems

Aerospace

• Replacing aluminum and other metals
• Large, high-precision parts can be molded efficiently without assembly
• Applications:
  • Engine components: withstand high temperatures and friction
  • External parts: rain erosion resistance
  • Internal parts: flame retardancy, low smoke/toxicity
  • Electrical systems: wire and fiber protection

Medical and Healthcare

• High wear, heat, chemical resistance, and electrical insulation
• Applications: dental instruments, endoscopes, dialysis equipment
• Examples:
  • Dental syringe handles and sterile boxes replacing aluminum
  • Withstands up to 3,000 high-pressure sterilization cycles at ~134°C
  • Maintains mechanical strength and hydrolytic stability
  • Improved biocompatibility for implants

Electrical and Electronics

• Excellent insulator for high reliability across temperature, pressure, and frequency variations
• Minimizes contamination in wafer processing
• Applications:
  • Coaxial connector sockets
  • Surface-mounted micro-adjust potentiometers (SMD)
  • Insulators for subsea environmental control equipment

Other Key Markets

• Outperforms metals in industrial, chemical, and processing components
• FDA-approved PEEK for food-contact applications
• Examples:
  • Replacing stainless steel impellers in regenerative pumps
  • Pipe and hose connectors for pressures up to 25,000 psi and temperatures up to 260°C