① General plastics generally refer to plastics with large output, wide use, good formability and low price.
② Engineering plastics generally refer to plastics that can bear certain external forces, have good mechanical properties, high and low temperature resistance and good dimensional stability, and can be used as engineering structures, such as polyamide and polysulfone.
③ Special plastics generally refer to plastics with special functions, which can be used in special application fields such as aviation and aerospace.