A coupled kinetic‐transport model for inhibiting etherification in synthesis of polyethylene naphthalate

During the polycondensation of polyethylene naphthalate (PEN), diethylene glycol (DEG) units induced via etherification side reactions significantly weaken the thermal properties of the resulting PEN. The DEG content is determined by both the polymerization rate and the mass transfer of condensation by‐products, and decoupling these two processes is essential to minimize DEG formation. In this study, we developed a coupled kinetic and transport model by introducing a fraction factor ( f i ) to quantitatively describe the partitioning of ethylene glycol molecules between diffusive mass transfer and participation in etherification side reactions. The maximum of f i together with its uncertainty bounds defines an optimal reaction temperature window at which ethylene glycol preferentially undergoes mass transfer rather than etherification, thereby minimizing DEG formation. The optimized PEN exhibits a low DEG content of 0.388%, 49% lower than values reported in previous studies (0.76–1.35%). This model clarifies DEG formation mechanisms and guides industrial PEN production.