Polyetheretherketone (PEEK) is an engineering thermoplastic with an unusual combination of properties- high mechanical strength, fatigue and creep resistance, excellent chemical resistance, and the ability to perform in high temperatures. It is so robust and does so many things well, it is the most utilitarian ‘Swiss Army Knife’ in the high performance material thermoplastic group.
First synthesized in 1978 by Victrex, it quickly became an excellent alternative to imidized materials (VESPEL® PI, Torlon® PAI). Offering lower cost and superior chemical and hydrolysis (steam) resistance, PEEK is an ideal material for seals, bearings and insulators in oil/gas/chemical processing and other high temperature/pressure applications. PEEK offers higher strength than fluoropolymers (Teflon®) at room and elevated temperatures.
There was only one resin source at the time, so pricing was high and general industry acceptance was slow. In recent years, new sources have introduced PEEK based materials, reducing the price and accelerating application development, making it attractive to more markets.
Processing techniques have also increased with shapes now being available via injection molding, extrusion, and compression molding.
Unfilled PEEK has the highest toughness and elongation of all the PEEK materials, and by itself has good bearing & wear properties. The most popular filled grades are 30% glass filled, 30% carbon fiber filled and a bearing grade with a carbon/graphite/PTFE additive package.
The addition of fiber reinforcement gives PEEK dimensional stability approaching that of metals.
Here’s a brief comparison of the properties of extruded PEEK variant shapes (at 73⁰F):
PROPERTY | Unfilled PEEK | 30% Glass Filled PEEK | 30% Carbon Filled PEEK | Bearing Grade PEEK |
Tensile Strength | 16,000 | 14,000 | 19,000 | 11,000 |
Elongation % | 40 | 2 | 5 | 2 |
Flexural Strength | 25,000 | 23,000 | 26,000 | 27,500 |
Heat Deflection Temperature ⁰F | 320 | 450 | 518 | 383 |
Coefficient of Thermal Expansion | 2.6 | 1.2 | 1.0 | 1.7 |
Dynamic Coefficient of Friction | .32 | n/a | .20 | .21 |
| Relative Wear Rate | 375 | n/a | 150 | 100 |
PEEK products are found in highly critical applications from High-Performance Liquid Chromatography columns to food applications as unfilled PEEK is FDA and USDA compliant. It is one of the few plastics compatible with ultra-high vacuum applications, which makes it suitable for aerospace applications ultra-pure specialty grade PEEK is considered an advanced biomaterial used in medical implants, used with a high-resolution magnetic resonance imaging (MRI), and for creating a partial replacement skull in neurosurgical applications.
Have a need for high performance at high temperatures? Call the experts at WS HAMPSHIRE to walk you through the candidate material selection process. You’re in the right place!
Tom Connelly is a self proclaimed “Street Engineer’ with over 40 years in the plastics industry.