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Poly ether ether Ketone (PEEK) is an aromatic semi-crystalline linear thermoplastic polymer composed of repeating units of polyaryletherketone (PAEK). Polyetheretherketone has a regular structure, and contains benzene rings, ether bonds and carbonyl groups on the molecular chain. In its polymer, the p-phenylene groups are connected by oxygen bridges (ether and ketone). Due to its special molecular structure, polyetheretherketone has the characteristics of heat resistance, radiation resistance, chemical resistance, and high mechanical strength. Polyetheretherketone can usually be prepared by polycondensation reaction of 4,4'-difluorobenzophenone and hydroquinone under the conditions of alkali metal carbonate and diphenylsulfonium as solvent. Due to its excellent performance, polyetheretherketone is widely used in aerospace, electronics, biomedicine, automotive industry, petrochemical industry and other fields.
Polyaryletherketone is a kind of thermoplastic high-temperature resistant engineering plastic with excellent comprehensive performance. It is the most widely used and largest polymer variety in the polyaryletherketone polymer family (PEK, PEEK, PEEKK, PEKK, PEKEKK). In 1962, DuPont of the United States first synthesized polyetherketoneketone (PEKK) by electrophilic substitution method, which started the research work of polyaryletherketone resins. In 1972, Imperial Chemical Industries (ICI) of the United Kingdom synthesized high molecular weight PEEK by nucleophilic substitution route of 4,4¡ä-difluorobenzophenone and hydroquinone, and started production in 1980. Subsequently, Victrex of the United Kingdom acquired the PEEK business from ICI in 1981 and sold PEEK under the brand name of Victrex, which officially started the commercialization process of polyetheretherketone resin. Subsequently, polyetheretherketone resins were developed by various companies. Among them, the Victrex PEEK product series has developed dozens of special derivative resins since its commercialization, and Victrex? PEEK resin has been certified by the European Aviation Standardization Committee, realizing the lightweight replacement of various parts in aviation equipment.
PEEK has been used for many years. By modifying and developing PEEK, it can have more excellent performance and be applied in different fields. Although PEEK resin has been industrialized as early as the late 1970s, only a few countries such as the United Kingdom, Germany, the United States, China, Japan, Switzerland, and India have truly mastered the PEEK resin synthesis technology. In addition to Victrex in the United Kingdom, PEEK manufacturers include EVONIK in Germany, SOLVEY in Switzerland, Mitsubishi Chemical in Japan, Sumitomo Chemical, DuPont in the United States, Gharda Chemical in India, Jida Special Plastic Engineering Research Co., Ltd. in Changchun, China, Jilin Zhongyan High-Performance Engineering Plastics Co., Ltd., and Panjin Zhongrun Special Plastic Co., Ltd.
Polyetheretherketone is composed of an amorphous phase and a crystalline phase, and its crystalline content depends on the heating process during the preparation of PEEK. Polyetheretherketone molecules contain ketone groups and ether groups, the bond angle of the molecular chain is 125¡ã, and the crystal is formed in a planar zigzag conformation. In the orthorhombic crystal cell of polyetheretherketone, the carbon long axis on its main chain contains 3 aromatic groups, and the center distance between the aromatic groups is 5 ?, corresponding to a long axis length of 15 ?. .
Polyetheretherketone is a thermoplastic aromatic semi-crystalline synthetic polymer with ketone and ether functional groups between the aromatic rings of its main chain. This special chemical structure gives PEEK stable physical and chemical properties and therefore many excellent properties.
High temperature resistance is one of the most outstanding advantages of PEEK. Its melting point is 343 ¡æ, glass transition temperature is 143 ¡æ, long-term use temperature is as high as 260 ¡æ, instantaneous use temperature can reach 300 ¡æ, and it hardly decomposes in a short time at 400 ¡æ, which is much higher than ordinary plastics and engineering plastics. Compared with other high temperature resistant plastics such as polyimide (PI), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polyphenylene ether (PPO), etc., the upper limit of use temperature is nearly 50 ¡æ higher. PEEK also has outstanding heat aging resistance. After 3000 h of heat preservation at 250 ¡æ, the bending strength is almost unchanged.
PEEK has some of the best mechanical strength characteristics among engineering plastics, including: high tensile strength (above 90 MPa), high elastic modulus, high hardness, impact resistance and creep resistance. In addition, PEEK can still maintain high strength at high temperatures. The bending strength at 200 ¡æ can still reach 24 MPa, and the bending strength and compression strength at 250 ¡æ can reach 12 to 13 MPa. It is particularly suitable for manufacturing components that can work continuously at high temperatures. PEEK not only has the characteristics of high strength and large modulus, but also has excellent toughness, impact resistance, creep resistance, fatigue resistance and other properties. Its excellent fatigue resistance to alternating stress is the most outstanding among all plastics and can be comparable to alloy materials. Its comprehensive mechanical properties are higher than those of other thermoplastic resins.
PEEK resin has outstanding tribological properties, certain self-lubricating properties and low friction coefficient, extremely low wear rate, and excellent resistance to sliding wear and micro-wear. In particular, it still maintains good tribological properties at 250 ¡æ, making it suitable for use in applications that strictly require low friction coefficient and wear resistance.
PEEK has very good chemical stability and excellent resistance to various organic solvents, oils, weak acids and weak bases. It is almost insoluble in other acids, bases and organic solvents except concentrated sulfuric acid. Its corrosion resistance is similar to that of nickel steel, and it can maintain strength over a wide temperature range and concentration. It has been proven to be a polymer that is difficult to discolor, swell or rupture.
PEEK has a very stable chemical structure and excellent radiation resistance. PEEK parts can also work normally under high doses of ionizing radiation. PEEK can withstand an irradiation dose of 1100 Mrad without losing its performance, which exceeds the general radiation-resistant material polystyrene. And it can resist gamma ray and electron beam radiation, which are mostly used for sterilization of medical equipment.
PEEK also has good hydrolysis resistance and maintains very low saturated water absorption over a wide temperature range. PEEK can resist chemical damage caused by seawater or high-pressure steam, and will not hydrolyze even in high temperature and high humidity environments. It can withstand more than 1,500 steam sterilization (autoclave) cycles at 134¡ãC.
PEEK resin is a very stable polymer. A 1.45 mm thick sample can reach the highest flame retardant standard without adding any flame retardant. PEEK's flame retardancy reaches UL 94V-0 level, and its limiting anaerobic index (LOI) is 35. It releases less smoke and toxic gases when burning, and is also self-extinguishing.
PEEK polymer exhibits high volume resistivity and surface resistivity, and can maintain good insulation properties over a wide temperature range and environmental changes. PEEK can maintain unchanged electrical properties over a wide frequency and temperature range. The dielectric constant of PEEK is 3.2~3.3, the dielectric loss is 0.0016 at 1k Hz, the breakdown voltage is 17 KV/mm, and the arc resistance is 175 V. Due to its excellent electrical insulation properties, PEEK can be used as a Class C insulating material.
PEEK material is non-toxic and is a biocompatible material. It is also the best long-term bone transplant material certified by the US FDA. PEEK is easy to adapt to the human body and can improve the success rate of medical applications, such as prostheses, stents and other medical implants. PEEK implants will not cause harmful effects when used in patients. It will not release toxic metal ions or particles after being corroded in the body like metal implants, causing allergic reactions or toxic effects.
PEEK has a small thermal expansion coefficient, and its products have good dimensional stability, which is very close to that of metal aluminum.
PEEK's easy processability has made it widely recognized in a large number of commercial applications. Due to its good high-temperature fluidity and high thermal decomposition temperature, it can be processed by the following methods: injection molding, extrusion molding, compression molding, blow molding, melt spinning, rotational molding, powder spraying, etc., and is often used to produce parts with complex geometries.
The industrial preparation method of polyetheretherketone (PEEK) is to condense equimolar amounts of aromatic halides 4,4'-difluorobenzophenone (DFBP) and hydroquinone (HQ) in a solvent diphenyl sulfone (DPS) under essentially anhydrous conditions. Sodium-containing inorganic salts, potassium carbonate, bicarbonate or high alkali metal carbonate can be used as catalysts for this reaction. During the reaction, the reactants need to be heated and stirred between 180 ¡ãC and 320 ¡ãC, and the solid reaction product finally obtained needs to be washed with acetone and water, and finally washed with acetone/methanol solution. The reaction process and reaction equation are as follows:
Polyetheretherketone (PEEK) can be prepared by electrophilic substitution reaction. PEEK can be prepared by dissolving and condensing 4-(4-phenoxy)benzoic acid in fluoroalkanesulfonic acid (trifluoromethylsulfonic acid) (TFMSA), or by reacting and condensing 1,4-diphenoxybenzene and 1,4'-di(4-carboxyl)phenoxybenzene in TFMSA. The obtained product is stirred in a certain concentration of sodium hydroxide solution, and then filtered, evaporated water and vacuum dried to obtain pure PEEK. In the BF?/HF catalytic system, PEEK can be prepared by polycondensation of 1,4-diphenoxybenzene with a derivative of thio or dithiocarbonic acid in a polar solvent, followed by dissolution, filtration, evaporation and drying to obtain pure PEEK.
Under anhydrous conditions, PEEK can be prepared by reacting a dibasic metal salt of a dihydric phenol with a dihalogenated benzene compound having an electron-withdrawing group at the ortho or para position. This reaction needs to be carried out in an organic solvent with high polarity, and dimethyl sulfoxide (DMSO) is commonly used as a solvent. This synthetic route does not require a catalyst. In the reaction, the dibasic metal salt of a dihydric phenol can be directly synthesized by an alkali metal oxide or an alkali metal hydroxide (such as potassium hydroxide) and hydroquinone in the organic solvent of the reaction, and the water formed during the reaction is removed by azeotropic distillation. PEEK can also be prepared by condensation reaction of 4,4'-difluorobenzophenone with a bistrimethylsilyl derivative of hydroquinone (1,4-bis(trimethylsilyloxy)benzene) at 220 - 320 ¡ãC. This route allows the synthesis of high purity PEEK, as the volatile trialkylfluorosilane generated during the reaction escapes from the reaction vessel at the reaction temperature.
PEEK can be synthesized by removing bulky substituents from soluble amorphous prepolymers. During the synthesis, at least one benzene ring in the PEEK prepolymer is substituted with a bulky group, which is then removed in a subsequent separation step. For example, under the conditions of anhydrous potassium carbonate as a base and a reaction temperature of 170 ¡ã C, an alkyl-substituted aromatic diol (tert-butyl hydroquinone) and 4,4¡ä-difluorobenzophenone are condensed in DMSO or cyclopentane sulfone as a solvent, and then the tert-butyl group of the polymer is removed with a Lewis acid (such as TFMSA) to obtain high-purity PEEK.
Polyetheretherketone can replace aluminum and other metal materials to manufacture various aircraft parts. Polyetheretherketone has a low density and good processing performance, so large parts requiring fineness can be directly processed and formed. PEEK is resistant to high temperatures and can withstand friction with dry or lubricating materials, so it can be used as a key engine part; in aircraft external parts, PEEK has excellent resistance to rain erosion; in internal components, its inherent flame retardancy and low smoke and low toxic gas emissions reduce the risk of fire; the polymer is used to manufacture gyrotrons to protect the wires and optical fiber filaments of aircraft electrical systems.
PEEK has excellent electrical properties, making it an ideal electrical insulator. PEEK can provide long-term operational reliability for parts within a wide range of temperature, pressure and frequency fluctuations. Its inherent purity combined with excellent mechanical and chemical stability minimizes contamination and improves safety during the processing of silicon wafers. Excellent thermal properties enable PEEK polymer parts to withstand high temperatures during welding. PPEK can be used for inlay plugs, high-reliability connectors, cable plugs, junction boxes, wiring leads, cage coils for plates, battery casings, etc. In the semiconductor industry, PEEK is used to manufacture wafer carriers, electronic insulation films and various connecting devices, used for wafer carrier insulation films, connectors, printed circuit boards, high-temperature connectors, etc. In addition, it can also be used in the transportation and storage equipment of microgram-per-liter ultrapure water, such as pipes, valves, pumps and containers.
Due to its good biocompatibility, corrosion resistance, thermal stability and excellent mechanical properties, polyetheretherketone has a wide range of applications in the medical field. The polymer can withstand up to 3,000 autoclave sterilization cycles, where the temperature is usually as high as 134 ¡ãC; in the presence of hot water, steam, solvents and chemicals, it can maintain excellent mechanical strength, excellent stress cracking resistance and hydrolytic stability, which improves the biocompatibility of implants. It can be used as an implant in orthopedics, artificial bones, medical catheters, intervertebral fusion devices, orthopedic bone plates, heart valves and stents, and dentistry.
PEEK's important performance advantages are excellent mechanical properties over a wide temperature range, easy processing and excellent fatigue resistance. It can replace metal as a raw material for manufacturing engine inner covers. Various parts such as under-hood piston units, bearings, gaskets, seals, gearboxes, clutch rings, etc. made of it are widely used in automobile transmission, brake and air-conditioning systems.
PEEK is often used to make compressor valves, piston rings, seals and various chemical pump bodies and valve parts. Using PEEK instead of stainless steel to make the impeller of the vortex pump can significantly reduce the degree of wear and noise level and extend the service life. Typical PEEK products include bearing cages, metal bearing linings, clutch parts, vacuum parts of power brakes, pulley loader blades, copier parts, liquid chromatograph filling columns and ultra-fine tubes for connection. Taking advantage of its good resistance to hot water and chemicals, it can be used to manufacture pump bodies and impellers and other parts of hot water and chemical pumps, steam valve O-rings, boiler pH meter sheaths, microscope lampshades, motor wire brackets, rocket battery slots, bolts, nuts and laboratory tweezers, etc.
PEEK has the characteristics of high temperature resistance, not easy to hydrolyze, and radiation resistance, so the wires, cables, ring skeletons, etc. made of it have been successfully used in nuclear power plants. In the oil exploration and production industry, it can be used to manufacture probes of special geometric dimensions involved in production machinery, connectors for oil production, etc.
PEEK can be made into powder coatings and water-based coatings, which can be applied to metal surfaces by brushing, thermal spraying, electrostatic spraying, electrophoretic deposition, etc., to obtain metal PEEK powder coating products with heat resistance, water resistance, good insulation, and strong corrosion resistance, such as oil pump plungers, pipes, reactors, water pumps, bearings, valves, etc., which are widely used in chemical corrosion protection, electronics, machinery and other fields.
PEEK is inert and has good biocompatibility. It is considered to be the preferred medical material for direct contact with organisms during chemical analysis or surgical operations. Its products will not cause adverse reactions or release of ion components, nor will they cause allergic reactions or toxic reactions, so they will not harm the human body.
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