Crystallization kinetics of poly(trimethylene terephthalate)

The isothermal crystallization kinetics of poly(trimethylene terephthalate) (PTT) have been investigated using differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Enthalpy data of exotherm from isoth ermal crystallization were analyzed using the Avrami theory. The average va lue of the Avrami exponent, n, is about 2.8. From the melt, PTT crystallize s according to a spherulite morphology. The spherulite growth rate and the overall crystallization rate depend on crystallization temperature. The inc rease in the spherulitic radius was examined by polarized light microscopy. Using values of transport parameters common to many polymers (U* = 1500 ca l/mol, T-infinity = T-g - 30 degrees C) together with experimentally determ ined values of T-m(0) (248 degrees C) and T-g (44 degrees C), the nucleatio n parameter, k(g), for PTT was determined. On the basis of secondary nuclea tion analyses, a transition between regimes III and II was found in the vic inity of 194 degrees C (Delta T congruent to 54 K). The ratio of k(g) of th ese two regimes is 2.1, which is very close to 2.0 as predicted by the Laur itzen-Hoffman theory. The lateral surface-free energy, sigma = 10.89 erg/cm (2) and the fold surface-free energy, sigma(e) = 56.64 erg/cm(2) were deter mined. The latter leads to a work of chain-folding, q = 4.80 kcal/mol folds , which is comparable to PET and PET previously reported. (C) 2000 John Wil ey & Sons, Inc.