Kinetics of polycondensation and copolycondensation of Bis(3-hydroxypropyl terephthalate) and Bis(2-hydroxyethyl terephthalate)

The kinetics of polycondensation and copolycondensation reactions of bis(3-hydroxypropyl) terephthalate (BHPT) and bis(2-hydroxyethyl) terephthalate (BHET) as monomers were investigated at 270°C, in the presence of titanium tetrabutoxide (TBT) as a catalyst. BHPT was prepared by ester interchange reaction of dimethyl terephthalate (DMT) and 1,3-propanediol (PD). Applying second-order kinetics for polycondensation, the rate constants of polycondensation of BHPT and BHET, k11 and k22, were calculated as 3.975 and 2.055 min−1, respectively. The rate constants of cross-reactions in the copolycondensation of BHPT and BHET, k12 and k21, were obtained by using the results obtained from a proton nuclear magnetic resonance spectroscopy. The rate constants during the copolycondensation of BHPT and BHET at 270°C decreased in the order k11 > k12 > k22 > k21, indicating the block nature of the copolycondensation.