Development Of Polyimide Film in Locomotive Traction Motor in China
Aug 29, 2022
In recent years, with the development of high and new technologies, especially Aerospace_ Polyimide film has played a very important role in the development of industry, electrical and electronic industry and information industry. Polyimide film is the most important insulating material in variable frequency motors. Polyimide is an aromatic heterocyclic polymer containing polyimide group in the repeating unit. Because of the very stable aromatic heterocyclic structural units in polyimide molecules, it has excellent properties that other polymers can not match.
(1) The heat resistance of polyimide is very good. The polyimide synthesized from biphenyl dianhydride and p-phenylenediamine has a thermal decomposition temperature of 600 ℃. It is one of the most thermally stable varieties of polymers so far. It can withstand 555 ℃ for a short time while basically maintaining its physical properties. It can be used for a long time below 333 ℃.
(2) The polyimide can withstand extremely low temperatures, and will not crack even in liquid helium at 269 ℃.
(3) Polyimide has high mechanical strength, and the tensile strength of unfilled plastics is more than 150 MPa. The film (Kapton) of homobenzene polyimide is 170 MPa, and the biphenyl polyimide (ijpiex s) reaches 400 MPa. As long-range plastics, the elastic modulus is usually 3-4 GPA, and the fiber can reach 200 GPa. According to theoretical calculation, the fiber synthesized from pyromellitic anhydride and p-phenylenediamine can reach 500 GPA, which is second only to carbon fiber.
(4) Polyimide has stable chemical properties, some varieties are insoluble in organic solvents, stable to dilute acids, hydrolysis resistant, and can withstand boiling at 120 ℃ for 500 H.
(5) Polyimide has strong creep resistance, and its creep speed is even lower than that of aluminum at higher temperatures.
(6) Polyimide has good radiation resistance, is stable under high temperature, high vacuum and irradiation, and has less volatile matter × The intensity retention rate was 90% after 1010 rad fast electron irradiation.
(7) Polyimide has excellent friction performance. When it rubs with metal under dry friction, it can transfer to the friction surface and play a self-lubricating role. Moreover, the static friction coefficient is very close to the dynamic friction coefficient, and the ability to prevent creep is good.
(8) Polyimide has excellent dielectric properties, with a dielectric constant of about 3.4, a dielectric loss of 10-3, and a dielectric strength of 100-200 kV / mm. These properties can be maintained at a high level over a wide temperature range and frequency range.
(9) Polyimide is a self extinguishing polymer with low smoke rate.
(10) Polyimide outgassing volume is very small under extremely high vacuum.
(11) Polyimide is non-toxic, can be used to make tableware and medical appliances, and can withstand thousands of disinfection. Some polyimides also have good biocompatibility. For example, it is non hemolytic in the blood compatibility test. The cytotoxicity test in vitro was non-toxic.
When polyimide is used in variable frequency motor, high frequency electric pulse will inevitably be generated due to variable frequency speed regulation technology, and its side effects will have a huge impact on the insulation performance of polyimide. Therefore, whether a new type of PD resistant material can be found to replace the traditional insulation material will become a key factor affecting the continued promotion and development of variable frequency motors.
