The optimal temperature and pressure conditions to effectively synthesize high molecular weight polyethylene terephthalate PET from terephthalic acid and ethylene glycol are as follows:1. Temperature: The synthesis of PET typically occurs in two stages. In the first stage, which is the esterification reaction, the temperature range is between 240-260C. In the second stage, which is the polycondensation reaction, the temperature range is between 270-290C.2. Pressure: The esterification reaction occurs at atmospheric pressure. However, during the polycondensation reaction, a reduced pressure of around 0.1-2.0 torr 0.013-0.27 kPa is applied to facilitate the removal of byproducts and promote the formation of high molecular weight PET.It is important to note that the exact temperature and pressure conditions may vary depending on the specific catalysts and process conditions used in the synthesis.