Introduction To The Properties Of PI Materials

  Aromatic polyimide is a kind of super engineering plastics with excellent comprehensive properties (long-term service temperature is above 250 ℃), and it has excellent mechanical, thermal, dielectric, wear resistance and weather resistance characteristics, so it is called "problem-solving expert". Its outstanding comprehensive performance, widely used in aerospace, automotive, electronics and other fields. Most polyimides are insoluble or insoluble and difficult to process. As a kind of high-performance engineering plastics, thermoplastic polyimide gcpitm not only has excellent heat resistance, mechanical, dielectric, corrosion resistance and radiation resistance, but also shows excellent hot working characteristics. It can be molded by hot pressing, extrusion and injection molding. Gcpitm is compounded with carbon fiber, glass fiber, polytetrafluoroethylene and graphite, which can significantly improve the mechanical strength, self lubrication and wear resistance of the material.

  1. The initial decomposition temperature of all aromatic polyimide is about 500 ℃ according to thermogravimetry. Polyimide, synthesized from biphenyl dianhydride and p-phenylenediamine, has the highest thermal stability in polymer at a temperature of 600 ℃.

  2. Polyimide can withstand extremely low temperature, such as in liquid helium at -269 ℃ will not crack.

  3. Polyimide has excellent mechanical properties, and the tensile strength of unfilled plastics is over 100MPa, the film of homobenzene polyimide is over 170Mpa, while that of biphenyl polyimide (upilex s) is 400MPa. As engineering plastics, the elastic film is usually 3-4gpa, and the fiber can reach 200GPa. According to the theoretical calculation, the fiber synthesized by the isophthalic anhydride and p-phenylenediamine can reach 500gpa,second only to carbon fiber.

  4. The thermal expansion coefficient of polyimide is 2 × 10-5－3 × 10-5, Guangcheng thermoplastic polyimide 3 × The results showed that the biphenyl type was 10-6 ℃ and 10-7 for individual varieties.

  5. Some polyimide varieties are insoluble in organic solvents, stable for dilute acids, and general varieties are not resistant to hydrolysis. However, the performance of this seemingly defective makes polyimide different from other high-performance polymers. It can be used to recover raw materials dicalch and diamine by alkaline hydrolysis, for example, for Kapton films, the recovery rate can reach 80% - 90%. The varieties with high hydrolysis resistance can be obtained by changing the structure, such as 120 ℃ and 500 hours water boiling.

  6. Polyimide has a high radiation resistance, and its film is in the range of 5 × After 109 rad fast electron irradiation, the intensity retention rate is 90%.

  7. Polyimide has good dielectric properties, and the dielectric constant is about 3.4. The dielectric constant can be reduced to about 2.5 by introducing fluorine or dispersing air nano size in polyimide. The dielectric loss is 10-3, the dielectric strength is 100-300kv / mm, the GPI is 300kV / mm, and the volume resistance is 1017 Ω / cm. These properties can be maintained at a high level in a wide temperature range and frequency range.

  8. Polyimide is a self extinguishing polymer with low smoke rate.

  9. The amount of outgassing of polyimide is very small under extremely high vacuum.

  10. Polyimide is nontoxic and can be used to make tableware and medical appliances, and can withstand thousands of times of disinfection. Some polyimides also have good biocompatibility. For example, they are non hemolytic in blood compatibility test and non-toxic in vitro cytotoxicity test.