Chemical Structure and Properties
Polyether ether ketone, commonly known as PEEK, is an engineered thermoplastic polymer belonging to a class of polymers called polyaryletherketones (PAEKs). At the molecular level, PEEK contains aromatic ether and ketone functional groups arranged in a repeating pattern along the polymer chain. This unique chemical makeup gives PEEK several desirable properties.

The repeated aromatic ether and ketone groups within the PEEK polymer backbone make it highly stable at elevated temperatures. PEEK retains its shape and mechanical properties up to 260°C, with some performance even up to 320°C. Its high melting point of 343°C allows it to withstand short exposure to even higher temperatures without degradation. PEEK is also highly resistant to hydrolysis, most acids and bases, and has very low moisture absorption.

In addition to heat resistance, Polyether Ether Ketone (PEEK)  possesses impressive mechanical properties. It has high strength and stiffness similar to metals like aluminum but with greater toughness. PEEK has a tensile strength of 90-100 MPa, tensile modulus of 3.6 GPa, and impact strength above 45 kJ/m^2. Its fatigue resistance and creep resistance at high temperatures are also outstanding. These properties, along with chemical stability, make PEEK suitable for engineering applications that demand performance under harsh conditions.

Applications in Medical Devices
PEEK's excellent biocompatibility, strength, and ability to be modified through composites and blends have fueled its widespread use in medical devices. Orthopedic and spinal implants made from PEEK offer key advantages over metal implants. PEEK implants are non-allergenic, lightweight and durable enough for load-bearing applications while allowing less obstruction during postoperative imaging studies like MRI and CT scans compared to metal implants.

Spinal fusion cages and interbody fusion devices used in lower back surgeries are commonly made from PEEK. These devices provide structural support and stability to facilitate bony fusion. PEEK is rigid enough to maintain disc height and lordosis but has elasticity mimicking bone to reduce stress shielding. Its radiolucency also allows monitoring of fusion without metal artifacts obscuring views.

In hip and knee replacements, PEEK is gaining popularity as a bearing surface material alternative to cross-linked polyethylene or ceramic. PEEK bearings couple well with metallic femoral and tibial components. Wear studies show PEEK generates ultra-low wear debris and is more scratch resistant than traditional materials. Coupled with its strength, PEEK bearings offer longevity and natural joint movement.

Aerospace and Transportation Applications
PEEK's strength, low weight, and durability make it well-suited for demanding applications in the aerospace, automotive, and transportation sectors. Aircraft components like engine cowlings, inlet guide vanes, ductwork, and electrical panels are being manufactured from PEEK composites. PEEK withstands jet engine heat and vibration better than metals. Additionally, its radio frequency transparency allows integration of radio antennas within PEEK parts.

In high-performance cars and racing vehicles, PEEK is the material of choice for turbocharger housings and other hot components near engines. Its high heat deflection temperature of 260°C allows it to perform reliably even under severe heating conditions. Many F1 race cars now use PEEK composites for brake ducts, suspension components and other structural and safety critical parts.

The transportation industry is increasingly adopting PEEK for rail, marine, and off-highway vehicle applications. PEEK composites provide strength and corrosion resistance for rail undercarriages, tunnel boring machine parts, marine rudder stocks, and hydraulic components in construction and mining equipment. PEEK's fatigue and impact resistance at low temperatures make it suitable even for use in cryogenic vessels.

Electrical and Electronics Applications
PEEK's thermal and dielectric properties enable diverse electrical and electronics applications. PEEK printed circuit boards (PCBs) offer low-loss dielectric substrates ideal for high frequency applications such as 5G networking. Its resistance to moisture uptake and dimensional stability over temperature variations give PEEK PCBs long-term reliability.

PEEK is the insulation material of choice for connecting rods, bushings, and other components in downhole drilling motors. It withstands high pressures and drilling fluid temperatures exceeding 200°C experienced downhole. Subsea oil and gas components like connector housings, valve parts and manifolds also use glass or carbon reinforced PEEK for strength in corrosive environments.

PEEK thermoplastics find increasing use as housings and structural parts in industrial controls, power generation equipment, and electrical distribution gear. PEEK composite casings shield electronic circuits from water, dust, chemicals and temperature extremes while offering electromagnetic transparency. Its flame retardancy makes PEEK suitable for applications near ignition sources.

Processing and Market Potential
PEEK polymer is commercially produced through nucleophilic aromatic substitution or direct arylation methods. It can then be formed into products using common thermoplastic processing techniques like injection molding, extrusion, machining and 3D printing. Carbon or glass filled PEEK composites provide increased strength-to-weight ratios for structural applications.

The global PEEK market was valued at over $500 million in 2020 and is projected to grow at 8-10% annually through 2027. Expanding use of PEEK in aerospace, medical, automotive and other industries underpins this growth. As more designers recognize the benefits of PEEK over conventional materials, new product innovations will drive further market expansion in years to come. With its versatility across sectors and ability to perform reliably under extreme conditions, PEEK will play an increasingly critical role in future technologies.

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