Effect of antimony catalyst on solid-state polycondensation of poly(ethylene terephthalate)

The effect of antimony trioxide (Sb2O3) catalyst on the solid-state polycondensation (SSP) of poly(ethylene terephthalate) (PET) has been rigorously studied. It has been determined that the rate constant increases, while the activation energy decreases, linearly with increasing catalyst concentration within the range of 0–100 ppm Sb. The SSP rate reaches its maximum value at about 150 ppm Sb. The activation energies are 30.7 and 23.3 kcal/mol respectively for the uncatalyzed and fully catalyzed SSP. The frequency factor decreases with increasing catalyst concentration due to the decreased mobility of catalyzed end groups. A mechanism of Sb catalysis has been proposed to explain these observations.