Morphology and kinetics studies of spherulitization of polyethylene terephthalate

A modified method of registration of small‐angle scattering of polarized light using the principles of the Fraunhofer diffraction permits the study of fast processes of spherulitization with averaging from a large amount of the scattering elements (several million). With the aid of this method the dependencies on temperature of the growth rate of the spherulites and the lag time have been studied for isothermal crystallization from the melt and from the glassy state. It has been shown that the maximum growth rate of spherulites in the course of the crystallization from the melt is observed at 155°C, and that from the glassy state is observed at 190°C. The thermodynamic parameters of the secondary nucleation determining the spherulite growth have been established. The energies of the formation of the lateral surfaces of cylindrical nucleus in the crystallization from the glassy state, and from the melt were found, to be equal, (σu = 5.75 erg/cm2) and those for the end ones were different (in the first case σe is 5.5 erg/c2 and in the second one σe is 14 erg/cm2). The morphology of spherulites depends strongly on the initial state of the system and the crystallization temperature. Spherulites are observed to have polarizability ellipsoids oriented along the radius and at an angle of 45° to it; in the course of the growth of spherulites changes in ellipsoid orientation are possible.