Polyesters are condensation polymers that contain ester functional groups within a category of polymers, or more particularly, their main bonds. Ethylene glycol is added to one or more batch reactors along with the terilenic acid. If DMT (Dimethyl telephthalate) is used as a raw material to create polyester monomer, glycol and water are evaporated and removed from the reactor. The polyester monomer process continues by being shaken in more than one reactor. Polymerization is carried out under high temperature and increased vacuum. During polymerization, ethylene glycol is evaporated. They are widely used for fiber and yarn purposes. It is known as polyethylene telephthalate, abbreviated as PET, and when mixed with cotton is used by the textile industry in a wide range.