Polyethylene terephthalate PET is synthesized through a two-step process: esterification and polycondensation. The reaction between terephthalic acid and ethylene glycol involves the formation of an ester linkage, which then polymerizes to form PET.1. Esterification: In this step, terephthalic acid reacts with ethylene glycol to form bis 2-hydroxyethyl terephthalate BHET intermediate. The optimal temperature for this reaction is between 220-260C, and it is usually carried out at atmospheric pressure.2. Polycondensation: In this step, the BHET intermediate undergoes polymerization to form PET. The optimal temperature for this reaction is between 270-290C. The pressure should be reduced to create a vacuum, typically around 0.1-1.0 mbar, to facilitate the removal of byproducts ethylene glycol and water and drive the reaction towards the formation of high molecular weight PET.In summary, the optimal conditions for the synthesis of PET from terephthalic acid and ethylene glycol are temperatures between 220-260C for esterification and 270-290C for polycondensation, with atmospheric pressure during esterification and a vacuum 0.1-1.0 mbar during polycondensation.