Poly (trimethylene terephthalate) copolyester containing ethylene glycol moieties. Part 1: Crystallization kinetics and melting behavior

A copolyester was characterized to have 91 mol% trimethylene terephthalate unit and 9 mol% ethylene terephthalate unit in a random sequence by using C-13 NMR. Differential scanning calorimeter (DSC) was used to investigate the isothermal crystallization kinetics in the temperature range (T-c) from 180 to 207 degrees C. The melting behavior after isothermal crystallization was studied by using DSC and temperature modulated DSC (TMDSC). The exothermic behavior in the DSC and TMDSC curves gives a direct evidence of recrystallization. No exothermic flow and fused double melting peaks at T-c = 204 degrees C support the mechanism of different morphologies. The Hoffman-Weeks linear plot gave an equilibrium melting temperature of 236.3 degrees C. The kinetic analysis of the growth rates of spherulites and the morphology change from regular to banded spherulites indicated that there existed a regime II -> III transition at 196 degrees C. (C) 2007 Elsevier Ltd. All rights reserved.