Polyetherketones (PEK for short) are

polymer A polymer (; Greek ''poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and ...

s whose molecular backbone contain alternating

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...

(R-CO-R) and

Ether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again b ...

(R-O-R) functionalities. The most common are

Polyaryletherketone Polyaryletherketone (PAEK) is a family of semi-crystalline thermoplastics with high-temperature stability and high mechanical strength whose molecular backbone contains alternately ketone (R-CO-R) and ether groups (R-O-R). The linking group R be ...

s (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 as ...

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 transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle "glassy" state into a viscous or rub ...

and melting temperatures compared to other

plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...

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. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distin ...

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

gear A gear is a rotating circular machine part having cut teeth or, in the case of a cogwheel or gearwheel, inserted teeth (called ''cogs''), which mesh with another (compatible) toothed part to transmit (convert) torque and speed. The basic p ...

s, sealing rings, valve spring retainers,

impeller An impeller or impellor is a 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. In pumps An impeller is a rotating componen ...

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 printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich str ...

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 t ...

handles, hip joint

prostheses In medicine, a prosthesis (plural: prostheses; from grc, πρόσθεσις, prósthesis, addition, application, attachment), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through trau ...

. 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 acids, 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, t ...

water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous p ...

, hot water, and concentrated

alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic 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 ...

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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