What are the requirements of precision injection molding for injection molding machines?
TIME：2021-10-7
As a typical special engineering plastic, polyether ether ketone (PEEK) has excellent physical and mechanical properties. Compared with other high-temperature resistant plastics, peek has the highest heat-resistant grade and the best comprehensive performance among special engineering plastics, with a long-term heat-resistant temperature of more than 250 ℃. In addition, peek also has excellent self-lubricating, flame retardant and chemical resistance. Peek's excellent comprehensive performance makes it widely used in automobile, aviation, electronic information, transmission pipeline and other fields.
However, peek has the following problems in practical application:
(1) Poor surface adhesion, weak interface adhesion with filler, poor thermal conductivity, easy to cause thermal expansion, thermal deformation and thermal fatigue;
(2) The wear resistance still can not meet the needs of the project, such as support materials, sealing rings, valves, etc;
(3) The forming process is difficult. The melting temperature of PEEK is 334 ℃, the melting viscosity is large, the processing temperature is high, and the processing process is unstable.
With the development of technology in various fields, higher and higher requirements are put forward for the properties of materials. The research on the modification of PEEK and expanding its application range has become a research hotspot in the industry.
Main modification methods of PEEK
At present, the main modification methods of PEEK include polymer blending modification, fiber reinforcement modification, whisker modification, inorganic particle filling modification and synergistic modification.
polymer blending modification
Peek blends with other engineering plastics or some special engineering plastics. Although the blend composites can reduce the cost and optimize some properties such as wear resistance, they will greatly reduce other properties of peek.
Fiber reinforced modification
Carbon fiber (CF) and glass fiber (GF) are commonly used in fiber reinforced modified peek, but with the development of material technology, a large number of other fiber materials have emerged, such as PTFE fiber, steel fiber and so on.
Adding fiber reinforced materials to the polymer can effectively improve the wear resistance of PEEK Composites and reduce the production cost. However, there are some limitations in the production process of fiber-reinforced PEEK composites. For example, in the hot pressing process, fiber unity is easy to occur in the mixing process of fiber and peek, resulting in poor uniformity of the mixture.
Whisker reinforced modification
Whisker is a salt or metal oxide with a certain aspect ratio. It has a low price, and its macro is powder, while its microstructure is fibrous. When filled with polymer, it has a significant reinforcing effect different from the general powder filler.
However, the surface treatment technology of whiskers is not mature and still needs to be improved, so the realization of industrial production is low. In addition, Whisker Reinforced PEEK materials can improve the wear resistance of the composites, but will reduce other properties, such as impact properties.
Inorganic particle filling modification
When the particle size is reduced to nano size, various performance behaviors of the material will change qualitatively, and the wear resistance will be significantly improved. At present, many studies use Al2O3 particles to fill and strengthen peek materials.
In addition, other particles such as Si3N4, SiO2, MoS2 and Cu are filled to improve the processability and manufacturing process properties of the composites.
Application of PEEK
Oilfield field
Because peek after reinforcement and modification has been further improved in mechanical properties, chemical corrosion resistance, radiation resistance and high temperature resistance, it is widely used in some special fields. For example, peek reinforced by 30% glass fiber can withstand 200 ℃ temperature and 140MPa pressure, and has excellent chemical, electrical and radiation resistance to harsh environment. It is used as drilling materials in oil exploration.
Electronic and electrical field
Peek can still maintain good electrical insulation in harsh environments such as high temperature, high voltage and high humidity, and is not easy to deform in a wide temperature range. Therefore, peek is gradually applied in the field of electronics and appliances as an ideal electrical insulation material.
PEEK material is used to make the shell of aluminum electrolytic container, which can meet the requirements of lead-free welding technology in the electronic industry; The wafer cartridge made of PEEK material can control the dissipation of electrostatic charge, protect the wafer from damage, and protect the wafer from pollution caused by electrostatic attraction by reducing and preventing electrostatic accumulation.
Automotive field
Karcoma amaturen umbh company of Germany produces truck oil filter with 30% GF Reinforced PEEK composite with brand name of 450 GL 30, which has been successfully used in Mercedes Benz truck. Moreover, because it can maintain outstanding mechanical and fatigue performance in a wide temperature range, it is selected as the engine end cover for first-class square racing and the racing distributor gear produced by it, Compared with bronze alloy gear, the weight is reduced by 81%.
In addition, Robert Bosch umbh uses PEEK / CF instead of metal as the functional component of ABS. The lighter composite parts reduce the rotational inertia, minimize the reaction time, greatly enhance the reaction performance of the whole system, and reduce the cost compared with the metal parts previously used.
In addition, after inorganic and organic reinforcement and modification, some peeks are widely used in automobile friction parts such as automobile gears, bearings, piston rings, clutch gear rings and so on because of their superior friction properties.
Medical field
Peek resin has the advantages of non-toxic, light weight and wear resistance. It is the closest material to human bone and can be organically combined with human body. Therefore, peek resin and its composites have been deeply studied and applied in spine and joints as orthopedic implants in recent years.
Solvay launched a series of biomaterials for implantable medical devices called solviva, which provides products in long-term and permanent contact with body fluids and tissues in the human body, including four types of polymers. Zeniva peek is one of the plastics with the strongest biological stability, with high strength and stiffness, excellent toughness and fatigue resistance, Meet the requirements of ASTM f2026-07 for peek for surgical implants.
Aerospace field
Because of the special and excellent properties of PEEK materials, it has a wide range of applications in the field of aerospace. Using light peek thermoplastic can not only improve fuel efficiency and meet environmental protection requirements, but also make assembly faster and more reliable, and reduce operators and manufacturing costs, representing the future performance development trend.
At present, peek materials have been widely used in radar radome, fuel tank, cover plate, pipeline and fastening system. In 2017, ESA has launched a 3D printing CubeSat stereo small satellite project of PEEK materials, and is gradually promoting the commercial application of microsatellites.
