PI film characteristics of mica board

1. According to thermogravimetric analysis, the decomposition temperature of fully aromatic polyimide is generally around 500℃. The polyimide synthesized from biphenyl dianhydride and p-phenylenediamine has a thermal decomposition temperature of 600 ℃, which is one of the high thermal stability varieties of polymers so far.

2. Polyimide can withstand extremely low temperatures, such as not brittle and cracked in liquid helium at -269°C.

3. Polyimide has excellent mechanical properties. The tensile strength of unfilled plastics is above 100Mpa, the Kapton film (Kapton) is above 170Mpa, and the biphenyl type polyimide ( UpilexS) reaches 400Mpa. As an engineering plastic, the amount of elastic film is usually 3-4 Gpa, and the fiber can reach 200 Gpa. According to theoretical calculations, the fiber synthesized by phthalic anhydride and p-phenylenediamine can reach 500 Gpa, second only to carbon fiber.

4. Some polyimide varieties are insoluble in organic solvents, stable to dilute acids, and general varieties are not resistant to hydrolysis. This seemingly shortcoming performance makes polyimide a big difference from other high-performance polymers. The characteristic of this is that the raw materials dianhydride and diamine can be recovered by alkaline hydrolysis. For example, for the Kapton film, the recovery rate can reach 80%-90%. Changing the structure can also produce varieties that are quite resistant to hydrolysis, such as those that can withstand boiling at 120°C for 500 hours.

5. The thermal expansion coefficient of polyimide is 2×10-5-3×10-5°C, Guangcheng thermoplastic polyimide is 3×10-5°C, biphenyl type can reach 10-6°C, and individual varieties are available. Up to 10-7°C.

6. Polyimide has high radiation resistance, and its film strength retention rate is 90% after 5×109rad fast electron irradiation.

7. Polyimide has good dielectric properties. The dielectric constant is about 3.4. Introducing fluorine or dispersing air nanometer size in polyimide, the dielectric constant can be reduced to about 2.5. The dielectric loss is 10-3, and the dielectric strength is 100-300KV/mm. These properties can still be maintained at a high level in a wide temperature range and frequency range.