The product is a truly fully soluble polyimide (PI) without the precursor - polyamic acid. The glass transition temperature (Tg) of the product is 320-330 °C, the temperature of thermal weight loss is about 525 °C, the intrinsic viscosity is 0.5-0.7dl/g (in NMP, 30 °C test), the product is 100% imidized, pure solid powder. At room temperature, it is soluble in common solvents. The dissolved concentration can reach more than 20%.