The synthesis of polyethylene terephthalate PET from terephthalic acid and ethylene glycol typically involves two main steps: esterification and polycondensation. To achieve the highest yield and molecular weight of the resultant polymer, the optimal temperature and pressure conditions for each step are as follows:1. Esterification: In this step, terephthalic acid reacts with ethylene glycol to form bis 2-hydroxyethyl terephthalate BHET . The optimal temperature for this reaction is between 220-260C, and the pressure is typically atmospheric pressure 1 atm or 101.3 kPa .2. Polycondensation: In this step, BHET undergoes polymerization to form PET. The optimal temperature for this reaction is between 270-290C. The pressure should be reduced during this step to facilitate the removal of byproducts such as water or ethylene glycol and to promote the formation of high molecular weight PET. The pressure is typically reduced to 0.1-1.0 mmHg 0.013-0.133 kPa .By maintaining these temperature and pressure conditions during the synthesis process, you can achieve the highest yield and molecular weight of polyethylene terephthalate.