Using the Functional Group Approach

Reaction Mechanism In this section, the polymer segment approach, which is in the framework of functional group approaches is presented [38]. The model is 

On the basis of these functional groups, the following mechanism is assumed to represent the kinetics of the esterification process [7]. 

Reactions (4.6)-(4.9) represent the typical esterification reactions, while reaction (4.10) is the polycondensation reaction, occurring mainly in the second step of polyester formation. Finally, reaction (4.11) is a side reaction resulting in diglycol repeating units, with ether Hnkages in the oligomeric chain. ki(i = 1,6) and k. i = 1,5) representing the kinetic rate constants of the six elementary reactions (lmol min ). 

Development of the Mathematical Model In order to develop a mathematical model for the esterification reaction the following assumptions are made  

On the basis of the reaction mechanism Equations 4.6—4.11, the reaction rates can be expressed in terms of the different functional groups present in the reactor and the corresponding rate constants [38]. The terms in parentheses denote mole numbers of each component. 

---