In 1908, Boger and rebshaw first prepared polyimide (PI) by melt self polycondensation of aminobenzoic anhydride. But it was only in the 1950s that PI was widely used as a polymer material with excellent comprehensive properties. In 1955 DuPont applied for the first patent in the world concerning the application of PI in materials. Subsequently Du Pont developed a series of PI materials, such as polyisophthalides thin developed in 1961 Membrane, developed and produced polyisophtylimide plastic in 1964, has been developing rapidly in PI era. So far, P1 has been developed as the most widely used material in heat-resistant aromatic heterocyclic polymers.
As of 2000, there are more than 20 famous manufacturers of large varieties, including Du Pont, general electric and Amoco in the United States, BASF and Ciba geigy in Europe, Dongli, Hitachi chemical, Zhongyuan, xuhuacheng industry, synthetic rubber company, Mitsui Dong pressure, Nissan Chemical, Shiji chemical, Yubu industry and Dongli Industrial company in Japan.
PI has superior comprehensive performance, so it is widely used in high-tech fields such as aviation, aerospace, machinery, petrochemical industry, microelectronics and so on. For example, PI can be used as gas separation film with high permeability and selectivity, orientation arrangement agent for vertical arrangement of liquid crystal molecules and photoresist directly photolithography into micro graphics. In addition, the PI can be reinforced with glass fiber, graphite and boron fiber to obtain higher hardness and strength, which can replace metal to make jet engine structural parts [3,4]. The excellent comprehensive properties of PI make PI one of the research points of high performance polymer. In recent years, people attach great importance to PI resin, and the research and application of PI resin have been developed rapidly.
Shanghai haohang Chemical Co., Ltd. has also been researched in PI material industry at present. For example, diamine fluorene (CAS 15499-84-0), 2-nitro-1-naphthol (CAS 607-24-9) are important intermediates applied to PI materials.
The main chain of polyimide contains benzene ring and imide ring structure. Because of the electron polarization and crystallinity, PI has strong inter chain effect, which leads to the close accumulation of pi molecular chain, which leads to the following shortcomings: the traditional commercialized Pi is insoluble and insoluble and difficult to process; The film is dark in color (usually dark yellow or brown), poor optical performance (strong absorption when it is close to 500nm), which is difficult to meet the needs of optical waveguide and optical communication field; the dielectric constant is high, which is difficult to meet the needs of the rapid development of K in modern microelectronics industry; the curing temperature is too high, and the synthesis process requires high. In addition, due to the high cost of raw materials and high production cost, the intermediate product, polyamide acid (PPA), is easy to decompose when it is in water, and it needs cold storage at low temperature, which is difficult to transport and save. In order to solve these problems, develop new performance and application fields of PI and adapt to the development of high technology, the research of PI is also developing towards the direction of high performance, multi-function and easy processing.
