PEEK (polyetheretherketone)polymers are carving out niches to replace metals in a variety of applications,particularly medical.

Asemicrystalline thermoplastic with excellent mechanical and chemical resistanceproperties at high temperatures, PEEK is used to makebearings, piston parts, pumps, compressor plate valves and cable insulation.It's one of the few plastics compatible with ultra-high vacuum applications.

"Thismaterial greatly improves the lifespan of sealing elements in the valve," says TimBremner, vice president of materials technology at Hoerbiger Corp., explainingselection of PEEK for a new application. "There is a dramatic increase in overallreliability and high-temperature performance when compared to other commonlyused valve plate materials."

New Series Targets Medical

Acombination of mechanical properties and excellent resistances withbiocompatibility are creating options for Vestakeep aromatic PEEK polymers inmedical applications. A new medical series from Evonik is described as suitablefor short-term body contact. The series includes a medium-viscosity grade, a high-viscositycompound and a powder grade. Engineers often specify PEEK as an inexpensive alternative to metals and othermaterials. PEEK is resistant to gamma rays or X-rays and offers X-raytransparency. Target applications includesurgical instruments and endoscopes.

Machined Shapes are Implantable

Stockshapes made of Zeniva PEEK from Solvay Advanced Polymers offer a combination ofbroad chemical resistance, high strength, stiffness, excellent toughness andfatigue resistance. They are aimed at close tolerance machining of finishedcomponents and for prototypes used in injection molding applications. PEEK is oneof four polymers that comprise the company's family of biomaterials beingoffered for use in implantable medical devices. They comply with ISO 13485manufacturing and meet current Good Manufacturing Practices (GMP).

CFRP PEEK Makes a Tough Valve

HoerbigerCorp., the world's largest independent compressor valve manufacturer, is usinglow-flow, carbon-fiber-reinforced PEEK compound to create a tough compressorvalve plate withhigh thermal and dimensional stability. Tim Bremner, vice president ofmaterials technology at the OEM, says, "Valve plate materials must providea high degree of physical strength while maintaining high impact and cyclicfatigue resistance. In many instances,compressor plates compress highly acidic or caustic gas streams, posing seriouschallenges for the chemical compatibility of the valve plate material."The primary benefit of the PEEK compound from RTP Co. is the high flexuralmodulus achieved through careful incorporation of carbon fiber into the resinmatrix duringcompounding.