Polyetherketones (PEK for short) are

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

s whose molecular backbone contain alternating

ketone In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...

(R-CO-R) and

Ether In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R� ...

(R-O-R) functionalities. The most common are Polyaryletherketones (PAEK), in which there is an

aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used ...

group linked in the (1–4)-position between each of the functional groups. The backbone, which is thus very rigid, gives the materials very high

glass transition The glass–liquid transition, or glass transition, is the gradual and Reversible reaction, reversible transition in amorphous solid, amorphous materials (or in amorphous regions within Crystallinity, semicrystalline materials) from a hard and rel ...

and melting temperatures compared to other

plastic Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...

Synthesis

Polyetherketones can be obtained by condensation of 4,4′-difluorobenzophenone and potassium or sodium salt of

hydroquinone Hydroquinone, also known as benzene-1,4-diol or quinol, is an aromatic organic compound that is a type of phenol, a derivative of benzene, having the chemical formula C6H4(OH)2. It has two hydroxyl groups bonded to a benzene ring in a ''para' ...

: :

Types

The most common of these high-temperature resistant materials is polyetheretherketone (PEEK). Other types of polyetherketone are: * PEKK = Polyetherketoneketone * PEEKK = Polyether ether ketone ketone * PEKEKK = Polyetherketoneetherketoneketone

Applications

Space and aviation: aircraft parts (fins, wing flaps, nose caps, seats). Replacements for metal parts, also in the

military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. Militaries are typically authorized and maintained by a sovereign state, with their members identifiable by a d ...

field. Machinery and automotive industry: high-performance molded parts such as bearing cages,

gear A gear or gearwheel is a rotating machine part typically used to transmit rotational motion and/or torque by means of a series of teeth that engage with compatible teeth of another gear or other part. The teeth can be integral saliences or ...

s, sealing rings, valve spring retainers,

impeller An impeller, or impellor, is a driven rotor used to increase the pressure and flow of a fluid. It is the opposite of a turbine, which extracts energy from, and reduces the pressure of, a flowing fluid. Strictly speaking, propellers are a sub-clas ...

s. Coatings when high resistance to temperatures above 200 °C is required. Coatings made of PEEK or PEK, for example, are suitable for applications up to 230 °C (450 °F). Electronics industry: wire and cable sheathing, flexible

printed circuit board A printed circuit board (PCB), also called printed wiring board (PWB), is a Lamination, laminated sandwich structure of electrical conduction, conductive and Insulator (electricity), insulating layers, each with a pattern of traces, planes ...

s, semiconductor production, offshore connectors. Medical technology:

endoscope An endoscope is an inspection instrument composed of image sensor, optical lens, light source and mechanical device, which is used to look deep into the body by way of openings such as the mouth or anus. A typical endoscope applies several modern ...

handles, hip joint prostheses. Because polyetherketones can be sterilized without damaging them, PEK is often used for surgical applications.

Properties

PEK has a high temperature resistance. It is also characterized by high wear resistance. In addition, polyetherketones are highly resistant to chemicals: They are resistant to non-oxidizing

acid An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...

s, grease,

lubricant A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, ...

water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...

, hot water, and concentrated

alkali In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The a ...

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Literature

* Beland, S. (1990). ''High performance thermoplastic resins and their composites''. William Andrew. * Díez-Pascual, A. M., Naffakh, M., Marco, C., Ellis, G., & Gómez-Fatou, M. A. (2012). High-performance nanocomposites based on polyetherketones. ''Progress in Materials Science'', ''57''(7), 1106–1190.

References

Ethers Ketones Polymers