Crystallization regime behavior of poly(pentamethylene terephthalate)

Abstract

AbstractPoly(pentamethylene terephthalate) (PPT), a less studied aryl polyester, was synthesized by polycondensation and characterized by 1H NMR and gel permeation chromatography. The crystallization kinetics were investigated by means of differential scanning calorimetry and polarized light microscopy. The average value of the Avrami exponent was calculated to be 2.9, which indicated an athermal nucleation process followed by three‐dimensional crystal growth. The kinetics of spherulitic growth of PPT were analyzed with the Lauritzen–Hoffman (L–H) secondary nucleation theory, and the nucleation constants (Kg) for regimes II and III were thus determined from the slope of the L–H plot with an activation energy (U*) of 3500 cal/mol. The validity of the U* value was examined. Meanwhile, the existence of a transition from regime II to regime III at 95 °C was determined, and the value of Kg(III)/Kg(II) was 2.04. The equilibrium melting temperature of PPT was estimated to be 149.4 °C with the linear Hoffman–Weeks extrapolation method. The lateral surface free energy, fold surface free energy, and work of chain folding were estimated. These thermodynamic properties of PPT were then compared to those of other terephthalic polyesters. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1265–1274, 2004