Overall reaction equation
⇌ n CH₃OOC—C₆H₄—COOCH₃ + n HO—CH₂—CH₂—OH
Each PET repeat unit consumes 2 mol methanol → 1 mol DMT + 1 mol EG. Stoichiometric M/PET = 2; in practice 6-10× molar excess of methanol drives equilibrium and reduces melt viscosity.
