The English name of pyromellitic dianhydride is Pyromellitic Dianhydride (abbreviated as PMDA, the same below), which is mainly used to synthesize polyimide. Since polyimide has excellent ultra-high heat resistance, acid and alkali resistance, excellent mechanical properties, electrical properties and dimensional stability, it is widely used in high-tech fields such as aviation, aerospace, microelectronics and atomic energy that have strict requirements on material properties.