Polyimide (PI) refers to a class of polymers containing an imide ring (-CO-N-CO-) on the main chain. Among them, the polymers containing phthalimide structure are the most important and are comprehensive. One of the best-performing organic polymer materials. The high temperature resistance of PI is above 400℃, the long-term use temperature range is -269～260℃, some parts have no obvious melting point, and have high insulation performance.

Polyimide is listed as one of "the most promising engineering plastics in the 21st century", and its research, development and utilization have been included in the medium and long-term development plans of various advanced industrial countries.

Aromatic polyimide is an important material in the microelectronics industry. According to chemical composition, polyimides can be divided into aliphatic and aromatic polyimides. According to processing characteristics, polyimides can be divided into thermoplastic and thermosetting. Aromatic polyimide has the most stable thermal properties which is a commonly used polyimide material in the microelectronics industry. Polyamic acid or polyamide ester is obtained by imidization (cyclization) by a certain method.

Polyimide products have a wide range of applications. Polyimide products are mainly as format as films, composite materials, foamed plastics, engineering plastics, fibers, etc., which can be applied to aerospace, electrical insulation, liquid crystal display, automotive medical, atomic energy, satellites, nuclear submarines, microelectronics, precision machinery packaging, etc. many fields.