Polyaryletherketone plastics are also known as polyetherketone plastics, abbreviated as PAEK in English. There are many kinds of PAEK, and the main ones that have been developed are: polyetheretherketone (PEEK), polyetherketone (PEL), polyetherketone ketone (PEKK), phenolphthalein polyetherketone, polyetheretherketone (PEEEK) and polyetherketone etherketone ketone (PEKEKK), etc., the first four have been industrially produced.
PAEK plastics are a new type of heat-resistant engineering plastics with excellent comprehensive properties, high heat resistance level (can be used for a long time in the range of 200~260 °C), and good radiation resistance. The factor restricting its development is the high price, which is currently about 50~700,000 yuan/ton.
1. Introduction to polyaryletherketone (PEEK, PEK, PEKK).
PEEK is the only polyaryletherketone variety that can be produced in large quantities, while the output of PEK and PEKK is smaller. They are mainly used in electronic appliances, compressor parts, auto parts, mechanical parts and medical equipment.
2. Structural performance
(1) Structure PEEK, PEK, PEKK three varieties are linear structure, thermoplastics. On the one hand, the macromolecular backbone contains a large number of aromatic rings and polar ketone groups, and the molecular chain presents greater rigidity and strong intermolecular force, resulting in heat resistance and mechanical strength to the polymer. On the other hand, the macromolecule contains a large number of ether bonds, which gives the polymer toughness, and the more ether group content, the better its toughness, for example, PEEK has better toughness than PEKK.
(2) Performance The three varieties are crystalline plastics, which have high mechanical properties and tensile strength of more than 100MPa, but the rigidity is low at high temperature, and the strength decreases quickly with the increase of temperature, and the temperature drops sharply at 100~150 °C.
The stress cracking resistance of the three plastics is much better than that of polysulfone (PSF), polyarylsulfone (PES), polycarbonate (PC), modified polyphenylene ether (MPPO) and other varieties, and the creep resistance and fatigue resistance are higher than those of PES.
The three varieties have good heat resistance and can be used for a long time in the range of 230~260 °C; excellent electrical properties, can still maintain a small dielectric constant and dielectric loss at high frequency, so they can be used in high-frequency occasions; good radiation resistance, the performance is basically not affected by γ rays below 2×107GY; good flame retardancy, with self-extinguishing performance.
The chemical stability of the three varieties is good, which is better than that of PC, MPPO, PES and other varieties. It is resistant to any chemical agents except concentrated sulfuric acid and retains good corrosion resistance even at higher temperatures. They are insoluble in solvents such as acetone, trichloroethylene, xylene, chloroform, isoacetone and gasoline, but are not resistant to concentrated sulfuric acid. They have the best resistance to hot water and steam among all engineering plastics, and can be used for a long time in steam at 200°C or in high-pressure steam at 300°C for a short period of time.
3. Molding processing
PEAK is a thermoplastic with the processability of a molten plastic and can be molded by injection molding, extrusion and blow molding. PEAK has a high processing temperature and high melt viscosity, but the melt is thermally stable at processing temperature.
The processing conditions have a great influence on the crystallinity and crystal structure of the product, and the conditions that are conducive to improving the crystallinity should be used as much as possible in the processing to improve the mechanical properties of the product. PEAK requires drying before processing and post-processing to relieve internal stress.
4. Scope of application
(1) Electronic and electrical appliances Due to its excellent heat resistance and electrical properties, PEAK can be used for Class C (>180°C) insulating materials, including cable sheaths, marine cables, lubricating oil resistant wires for aircraft, high-temperature boiling water resistant wires, seawater corrosion-resistant wires, high-temperature binding posts, wiring boards, motor lining materials and capacitor films.
(2) Mechanical instrumentation Due to its high strength, PEAK can be used as a structural material, including bearing cages, sensors, piston rings, engine components, aircraft structural materials and parts. PEEK is blended with molybdenum disulfide and F4 for wear-resistant materials.
(3) Nuclear power plant can be used for various plastic products such as containers that are irradiated in nuclear power plants due to its good radiation resistance.
