Synthesis and non-isothermal crystallization kinetics of poly(ethylene terephthalate)-co-poly(propylene glycol) copolymers

Poly(ethylene terephthalate)-co-poly(propylene glycol) (PET-co-PPG) copolymers with PPG ratio ranging from 0 to 0.90mol% were synthesized by the melt copolycondensation. The intrinsic viscosity, structure, non-isothermal crystallization behavior, nucleation and spherulitic growth of the copolymers were investigated by Ubbelohde viscometer, Proton Nuclear Magnetic Resonance (H-1-NMR), differential scanning calorimetry, and polarized optical microscopy, respectively. The non-isothermal crystallization process of the copolymers was analyzed by Avrami, Ozawa, Mo's, Kissinger, and Dobreva methods, respectively. The results showed that the crystallizability of PET was apparently enhanced with incorporating a small amount of PPG, which first rose and then reduced with increasing amount of PPG in the copolymers at a given cooling rate. The crystallization mechanism was a three-dimensional growth with both instantaneous and sporadic nucleation. Particularly, PET-co-PPG containing 0.60mol% PPG exhibited the highest crystallizability among all the copolymers. Copyright (c) 2015 John Wiley & Sons, Ltd.