Cationic yarn belongs to modified polyester, the chemical name: polybutylene terephthalate (elastic polyester), abbreviation: PBT, which is also indicated by CD in the factory. Because ordinary polyester (polyethylene terephthalate) has low moisture absorption, poor dyeing performance, easy to accumulate static electricity, easy to fluff, etc., it is usually modified with sulfonate as a modifier to be dyed with cationic dyes. Polyester, or add cationic active agent to prepare modified polyester before or during spinning. This kind of yarn is called cationic yarn. This kind of yarn does not need high temperature dyeing like ordinary polyester, and can be dyed at normal temperature.